The information in this prospectus is not complete and may be changed. No securities may be sold until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities, and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

SUBJECT TO COMPLETION,

Dated: October , 2017June 30, 2021

PROSPECTUS

MoSys, Inc.

$10,000,000100,000,000

Common Stock

Warrants to Purchase CommonPreferred Stock

MoSys, Inc.Warrants

3301 Olcott StreetUnits

Santa Clara, CA 95054Subscription Rights

(408) 418‑7500

We may offer from time to time:

We may offer from time to time to sell the securities described in this prospectus separately or together in any combination, in one or more classes or series, in amounts, at prices and on terms that we will determine at the time of the other securities that may be sold under this prospectus.any such offering.

The securities we offer will have an aggregate public offering price of up to $10 million.$100,000,000. We will provide specific terms of any offering in supplements to this prospectus. The securities may be offered separately or together in any combination and as separate series. You should read this prospectus and any prospectus supplement carefully before you invest.

We may sell these securities on a continuous or delayed basis directly, through agents, dealers or underwriters as designated from time to time, or through a combination of these methods. We reserve the sole right to accept, and together with any agents, dealers and underwriters, reserve the right to reject, in whole or in part, any proposed purchase of securities. If any agents, dealers or underwriters are involved in the sale of any securities, the applicable prospectus supplement will set forth any applicable commissions or discounts. Our net proceeds from the sale of securities also will be set forth in the applicable prospectus supplement.

Our common stock is listed on the Nasdaq Capital Market, of the NASDAQ Stock Marketor Nasdaq, under the symbol “MOSY.” The last reported sales price of our shares of common stock on July 28, 2021 was $4.73 per share.

As

Investing in any of our securities involves a high degree of risk. Please read carefully the datesection entitled “Risk Factors” on page 5 of this prospectus and the aggregate market value of our outstanding common stock held“Risk Factors” section contained in any applicable prospectus supplement and in the documents incorporated by non-affiliates was approximately $7 million, based on 8,002,010 shares of outstanding common stock, of which approximately 7,819,427 shares were held by non-affiliates, and a price of $   per share, which was the last reported sale price of our common stock on The NASDAQ Capital Market on October   , 2017. As of the date ofreference in this prospectus we have sold $2,252,500 ofbefore investing in our securities pursuant to General Instruction I.B.6. of Form S‑3 during the prior 12 calendar month period that ends on, and includes, the date of this prospectus.securities.

INVESTING IN OUR SECURITIES INVOLVES RISKS.

SEE “RISK FACTORS” ON PAGE 6.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is                       October                     , 2017.2021.

TABLE OF CONTENTS

In this prospectus, “MoSys,” “we,” “us,”“us” and “our” refer to MoSys, Inc. and its subsidiaries.

You should rely only on information contained or incorporated by reference in this prospectus. We have not authorized any person to provide you with information that differs from what is contained or incorporated by reference in this prospectus. If any person does provide you with information that differs from what is contained or incorporated by reference in this prospectus, you should not rely on it. This prospectus is not an offer to sell or the solicitation of an offer to buy any securities other than the securities to which it relates, or an offer of solicitation in any jurisdiction where offers or sales are not permitted. The information contained in this prospectus is accurate only as of the date of this prospectus, even though this prospectus may be delivered or shares may be sold under this prospectus on a later date.

About This Prospectus

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or the SEC or the Commission, using a “shelf” registration process. Under the shelf process, we may, from time to time, issue and sell to the public any or all of the securities described in the registration statement in one or more offerings.

This prospectus provides you with a general description of the securities we may offer. Each time we offer securities, we will provide a prospectus supplement that will describe the specific amounts, prices, and terms of the securities we offer. The prospectus supplement also may add, update, or change information contained in this prospectus. This prospectus, together with applicable prospectus supplements, includes all material information relating to this offering. If there is any inconsistency between the information in this prospectus and the information in the accompanying prospectus supplement, you should rely on the information in the prospectus supplement. Please carefully read both this prospectus and any prospectus supplement together with the additional information described below under the section entitled “Where You Can Find More Information.”

We may sell the securities to or through underwriters, dealers, or agents or directly to purchasers. We and our agents reserve the sole right to accept and to reject in whole or in part any proposed purchase of securities. A prospectus supplement, which we will provide each time we offer securities, will provide the names of any underwriters, dealers or agents involved in the sale of the securities, and any applicable fee, commission, or discount arrangements with them.

Special Note Regarding Forward-Looking Statements

Some of the statements in this prospectus constitute forward-looking statements. These statements involve known and unknown risks, uncertainties, and other factors that may cause our or our industry’s actual results, levels of activity, performance, or achievements to be materially different from any future results, levels of activity, performance, or achievements expressed or implied by such forward-looking statements. These factors include, among others, those incorporated by reference under “Risk Factors” below.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expects,” “plans,” “anticipates,” “believes,” “estimates,” “predicts,” “potential,” or “continue” or similar terms.

Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity, performance, or achievements. Our actual results could differ materially from those expressed or implied by these forward-looking statements as a result of various factors, including the risk factors incorporated by reference under the heading “Risk Factors” below and a variety of other factors, including, without limitation, statements about our future business operations and results, the market for our technology, our strategy and competition.competition and the widespread outbreak of contagious diseases, including the outbreak in 2020 of a respiratory illness caused by a novel coronavirus known as COVID-19.

Moreover, neither we nor any other person assumes responsibility for the accuracy and completeness of these statements. We undertake no obligation to update or revise any of the forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law. In light of these risks, uncertainties and assumptions, the forward-looking events discussed or incorporated by reference in this prospectus may not occur.

Our Company

We were founded in 1991. Our principal executive offices are located at 3301 Olcott Street, Santa Clara, CA 95054.  Our telephone number at that address is (408) 418‑7500.

We are a fabless semiconductor company focused on the development and sale of integrated circuits, or ICs, for the high-speed cloud networking, communications, storagesecurity appliance, video, monitor and test, data center and computing markets. Our solutions deliver time-to-market, performance, power, area and economic benefits for system original equipment manufacturers, or OEMs. We have developed two families of ICsOur primary product line is marketed under the Bandwidth Engine®Accelerator Engine name and LineSpeed™ product names.comprises our Bandwidth Engine ICs combineand Programmable HyperSpeed Engine IC products, which integrate our proprietary, 1T-SRAM®1T-SRAM high-density embedded memory and a highly-efficient serial interface protocol resulting in a monolithic memory IC solution optimized for memory bandwidth and transaction access performance. Further performance benefits can be achieved to offload statistical, search or other custom functions using our optional integrated macro functionslogic and processor elements.

As data rates and the amount of high-speed processing increase, critical memory access bottlenecks occur. Our Accelerator Engine ICs dramatically increase memory accesses per second, removing these bottlenecks. In addition, the serial interface and high-memory capacity reduce the board footprint, number of pins and complexity, while using less power. To complement our Accelerator Engine ICs and utilize our technology we have been developing our Virtual Accelerator Engine, or VAE, product line that leverages our proprietary graph memory engine technology to provide data classification capabilities through the use of high-speed memories. Our VAE products include software, firmware and related intellectual property, or IP, and are hardware agnostic and operate with or without one of our Accelerator Engine IC products.

Our LineSpeed IC product line comprises non-memory, high-speed serialization-deserialization interface, or SerDes I/O, with our intelligent access technology and a highly efficient interface protocol. The LineSpeed IC product linephysical layer, or PHY, devices that ensure signal integrity between interfaces which is comprised of non-memory, high-speed SerDes I/O devices withcommonly referred to as clock data recovery, gearbox andor CDR, or retimer functionality, which convert lanes of data receivedperform multiplexing to transition from one speed to another, commonly referred to as Gearbox functionality. These PHY devices reside within optical modules and on networking equipment line cards designed for next-generation Ethernet and optical transport network applications.

The address and phone number of our principal executive offices are MoSys, Inc., 2309 Bering Drive, San Jose, CA 95131, (408) 418-7500.

COVID-19

The full effects of COVID-19 and other potential future public health crises, epidemics, pandemics or similar events are uncertain and could have a material and adverse effect on our business, financial condition, operating results and cash flows.

The global outbreak of the coronavirus disease 2019, or COVID-19, was declared a pandemic by optical modules into different configurationsthe World Health Organization and a national emergency by the U.S. government in March 2020. This has negatively affected the world economy, disrupted global supply chains, significantly restricted travel and transportation, resulted in mandated closures and orders to “shelter-in-place” and created significant disruption of the financial markets. The extent of the impact on our operational and financial performance will depend on future developments, including the duration and spread of the pandemic and related actions U.S. and foreign government agencies continue to take to prevent disease spread, all of which are uncertain, out of our control and cannot be predicted.

In accordance with applicable U.S. governmental ordinances generally exempting essential businesses and/or ensure signal integrity. Incritical infrastructure workforces from mandated closures and orders to “shelter-in-place,” we are operating in support of essential products and services, subject to limitations and requirements in applicable state and county orders. We have been complying with county and state orders and have implemented a teleworking policy for our employees and contractors and significantly minimized the quarter ended September 30, 2017,number of employees who visit our office. Since the outbreak of COVID-19, while we notifiedhave experienced increased lead times for wafers, substrates and assembly services, we have experienced minimal impact on our customers that we intendproduction operations and have been able to discontinue our LineSpeed IC product line. We are currently supporting existing LineSpeed IC customers and accepting last-time product orders. Going forward, we expect to focussatisfy all customer purchase orders timely. However, a facility closure, work slowdowns or temporary stoppage at one of our efforts onmanufacturing suppliers could occur, which could have a longer-term impact and could delay our Bandwidth Engine IC product line. Historically, our primary business was the design, development, marketing, sale and support of differentiated intellectual property, or IP, including embedded memory and high-speed parallel and SerDes I/O used in advanced systems-on-chips, or SoCs.

Our future successproduction and ability to achieveconduct business and maintain profitability are dependentnegatively impact our business, financial condition, operating results and cash flows.

If our workforce is unable to work effectively, including because of illness, quarantines, absenteeism, government actions, facility closures, travel restrictions or other restrictions in connection with the COVID-19 pandemic, our operations will be negatively impacted. We may be unable to produce and sell our IC products, and our costs may increase as a result of the COVID-19 outbreak. The impacts could worsen if there is an extended duration of any COVID-19 outbreak or a resurgence of COVID-19 infection in affected regions after they have begun to experience improvement.

The continued spread of COVID-19 has also led to disruption and volatility in the global capital markets. We may be unable to access the capital markets in the future, and additional capital may only be available to us on the marketingterms that could be significantly detrimental to our existing stockholders and sales ofto our Bandwidthbusiness.

Our Products

Accelerator Engines

Our Accelerator Engine IC products into networking, communicationsinclude the Bandwidth Engine, which is targeted for high-performance applications where throughput is critical, and other markets requiring high-bandwidth memory access.

We incurred a net loss of $4.0 million for the quarter ended June 30, 2017 and had an accumulated deficit of $222.4 million as of June 30, 2017. In addition, we incurred net losses of approximately $32.0 million and $31.5 million

forProgrammable HyperSpeed Engine, which combines the years ended December 31, 2016 and 2015, respectively. These and prior year losses have resulted in significant negative cash flows for almost a decade and have required us to raise substantial amounts of additional capital during this period. To date, we have primarily financed our operations through multiple offerings of common stock to investors and affiliates, as well as asset sale transactions. In March 2016, we entered into a 10% Senior Secured Convertible Note Purchase Agreement with the purchasers of $8.0 million principal amount of 10% Senior Secured Convertible Notes due August 15, 2018 (the "Notes"), at par, in a private placement transaction. The Notes bear interest at the annual rate of 10%. Accrued interest is payable semi-annually in cash or in-kind through the issuance of identical new Notes, or with a combinationfeatures of the two, at our option. Since issuance of the Notes, we have made the interest payments in-kind through the issuance of additional notes totaling approximately $0.8 million. Further, the Notes restrict our abilityBandwidth Engine with 32 RISC processors to incur any indebtedness for borrowed money, unless such indebtedness by its terms is expressly subordinatedallow user-defined functions or algorithms to the Notes in right of payment and to the security interest of the Note holder(s) in respect to the priority and enforcement of any security interest in our property securing such new debt; provided that the Note holder(s) security interest and cash payment rights under the Notes shall be subordinate to a maximum of $5 million of indebtedness for a secured accounts receivable line of credit facility under certain conditions.

We expect to continue to incur operating losses for the foreseeable future as we secure customers for and continue to investembedded in the commercialization of our Bandwidth Engine IC products. We will need to increase revenues substantially beyond levels that we have attained in the past in order to generate sustainable operating profit and sufficient cash flows to continue doing business without raising additional capital from time to time. As a result of our expected operating losses and cash burn for the foreseeable future, recurring losses from operations, and the need to repay the Notes and accrued interest in 2018, if we are unable to raise sufficient capital through additional debt or equity arrangements, there will be uncertainty regarding our ability to maintain liquidity sufficient to operate our business effectively, which raises substantial doubt as to our ability to continue as a going concern. There can be no assurance that such additional capital, whether in the form of debt or equity financing, will be sufficient or available and, if available, that such capital will be offered on terms and conditions acceptable to us. We are primarily focusing our resources on producing and selling our existing products, and have substantially curtailed new product development. If we are unsuccessful in these efforts, we will need to implement additional cost reduction strategies, which could further affect our near- and long-term business plan. These efforts may include, but are not limited to, further reducing headcount and curtailing business activities.Programmable HyperSpeed Engine.

Our Strategy

Our primary business objective is to be an IP-rich fabless semiconductor company offering ICs that deliver unparalleled bandwidth performance for next generation data center, networking and communications systems.

Our Products

Bandwidth Engine

The Bandwidth Engine is a memory-dominated IC that has been designed to be a high-performance companion IC to packet processors. While the Bandwidth Engine primarily functions as a memory device with a high-performance and high-efficiency interface, it also can accelerate certain processing operations by serving as a co-processor element. Our Bandwidth Engine ICs combine: (1) our proprietary high-density, high-speed, low latency embedded memory, (2) our high-speed serial interface technology, or SerDes, (3) an open-standard interface protocol and (4) intelligent access technology. We believe an IC combining our 1T-SRAM memory and serial I/Ointerface with logic and other intelligence functions provides a system-level solution and significantly improves overall system performance at lower cost, size and power consumption. Our Bandwidth Engine ICs can provide up to and over 4.56.5 billion memory accesses per second externally and 12 billion memory accesses per second internally, which we believe is more than twicethree times the performance of current memory-based solutions. They also can enable system designers to significantly narrow the gap between processor and memory IC performance. CustomersOur customers that design Bandwidth Engine ICs onto the line cards in their networking systems will re-architect their systems at the line-card level and use our product to replace traditional memory solutions. When compared with existing commercially available solutions, our Bandwidth Engine ICs may:

Our first generation Bandwidth Engine 2 IC or BE1, products contain 576 megabytes,megabits, or MB,Mb, of memory and use a serial I/OSerDes interface with up to 16 lanes operating at up to 10.3 Gbps12.5Gbps per lane. Variations of the BE1 can have up to two interface ports, with up to eight serial receiver and eight serial transmitter lanes per port for a total of 16 lanes of 10.3 Gbps SerDes interface. These ICs include an arithmetic logic unit, which can perform read-modify-write operations. We have been shipping our BE1Bandwidth Engine 2 IC products since 2012.2013. We have notified customers, however, that we intendcontinue to discontinuewin new designs for this device family, and expect these products to be our BE1 products. We expect to complete final shipments of our BE1 products byprimary revenue source for the end of 2018.foreseeable future.

Our second generation Bandwidth Engine 3 IC  BE2, products contain 576 MB1152Mb of memory and use serial I/Oa SerDes interface with up to 16 lanes operating at up to 15 Gbps25Gbps per lane. In addition to a speed improvement of up to 50%, the architecture enables several family member parts with added specialized features. To date, we have announced three unique devices in this product family:

MSR620 with burst features optimized for oversubscription buffer applications;

MSR720 with a write cache and memory coherency capability that allows for deterministic look-ups optimized for state and queue type applications; and

MSR820 with increased intelligence for lookup, metering and statistics applications by adding dual counters, atomic and extensive metering functions.

We have been shipping our BE2 products since 2013. These products represented the majority of our revenues in 2016. We expect our BE2 products to represent the majority of our revenues for the foreseeable future.

Our third generation Bandwidth Engine IC, or BE3, products contain 1152 MB of memory and use serial I/O with up to 16 lanes operating at up to 30 Gbps per lane. BE3 targets3 ICs target support for packet-processing applications with up to five billion memory single word accesses per second, as well as burst mode to enable full duplex buffering up to 400Gbps400 Gbps for ingress, egress and oversubscription applications. To date, we have announced three uniqueThe devices in this product family:provide benefits of size, power, pin count, and cost savings to our customers.

MSR630 enables high rate lookup or high-performance buffer capabilities; and

MSR830 offers additional offload capabilities for functions such as statistics and metering to increase performance and add features for next-generation networking and communications equipment; and

MSRZ30 builds upon the capabilities and performance of the MSR830, with data rates, interface protocol and data structures that are optimized for the EZchip NPS‑400 network processing unit, or NPU, and can increase memory bandwidth by up to 50%.

We commenced sampling of our BE3 products in 2016, and expect to qualify these products for mass production in the first half of 2018. We do not anticipate significant revenues from our BE3 products until 2019 or later.

Our Programmable Search Engine

We brought our Programmable SearchHyperSpeed Engine IC (“PSE”) products to market in early 2016 to further leverage our proven serial interface technology and high-density integrated memory with the processor engine architecture to enable high-speed customizable search, security, and data analysis functions for networking, security, and data center applications. Our PSEapplications, as well as new markets such as video and compute acceleration. The product architecture features 32 search-optimized processor engines, data flow schedulers, and over a

terabit of internal access bandwidth. The device leverages our GCI interface technology and high-density integrated memory (1152 Mb(1152Mb of 1T-SRAM®1T-SRAM embedded memory).

QPR

During 2020, we launched a new line of memory ICs, our quad partition rate, or QPR, family of low cost, ultra-high speed SRAM memory devices optimized for FPGA-based systems.

Our QPR memory technology features an architecture that allows for parallel accesses to multiple partitions of the memory simultaneously and allows access of up to 576 bits per read or write cycle. The PSE device’s 32 processor elements have direct accessQPR device includes four independent partitions per input/output and each partition functions as a stand-alone random-access SRAM. The high-performance interface, larger density and the multiple partitions work together to integrated tablesupport multiple independent functional blocks within an FPGA with one QPR device. The MoSys MSQ220 and MSQ230 QPR devices are ideally suited for random-access applications. MoSys also offers an optional FPGA RTL memory throughcontroller to simplify the interface to its high capacity 567Mb or 1Gb devices. We also offer an internal interconnectRTL memory controller that presents an SRAM-like interface to simplify the QPR design effort.

The target applications are FPGA-based and scheduler architecture. To date, we have not soldinclude a broad range of markets, including test and measurement, 5G networks, router, switching, security, computational storage, database acceleration, Big Data, aerospace and defense, advanced video, high-performance computing, machine learning and AI and other data-driven areas.

LineSpeed Flex PHYs

Our LineSpeed Flex family of 100G PHYs, is designed to support industry standards and includes gearbox, Multi-Link Gearbox, or MLG, and high density CDR/retimer devices designed to enable Ethernet and OTN line card applications to support the PSE in significant quantities,latest electrical and have suspended our efforts to qualify the PSE until we identify a lead customer.optical interfaces.

IP Licensing and Distribution

1T-SRAM

Historically, we have offeredlicensed our IT-SRAM memory and I/OSerDes interface technologies on a worldwide basis to semiconductor companies, electronic product manufacturers, foundries, intellectual property companies and design companies through product development, technology licensing and joint marketing relationships. We licensed our IP technology to semiconductor companies whocompanies. Most of these licensees incorporated our technology into ICs that they sold to their customers. Ascustomers, and, in the case of IT-SRAM licenses, pay a result of the change inroyalty to us for each IC shipped that incorporates our corporate strategy, since early 2012,technology. Royalty and other revenue generated from our legacy IP licensing activities have been limited,agreements represented 13% and we expect this to continue. However, for the six months ended June 30, 2017 and the year ended December 31, 2016, approximately 20% and 24%, respectively,7% of our total revenues were generated from licensingfor 2020 and royalties related2019, respectively.

Virtual Accelerator Engines

Recently, we announced our new VAE product line that consists of software, firmware and other IP, such as register-transfer level, or RTL, code and utilizes a common application programming interface and common RTL interface to facilitate platform portability. This new product line will include multiple function accelerator platform products, which target specific application functions and will use a common software interface to allow performance scalability over multiple hardware environments. These function accelerator platform products are hardware agnostic and operate with or without one of our Accelerator Engine ICs. For example, our VAE IP can run on a processing unit IC or FPGA that is not attached to a MoSys IC or an FPGA that is attached to a MoSys IC, such as the Bandwidth Engine or Programmable HyperSpeed Engine.

Our initial VAE product is our graph memory engine, or GME, accelerator IP, which is part of our packet classification platform, for performing embedded search and classification of packet headers. A typical use would be an alternative to ternary content-addressable memory, or TCAM, which is a specialized type of high-speed memory that searches its entire contents in a single clock cycle. While TCAMs enable the highest levels of performance, they are monolithic ICs that are limited in capacity and consume large amounts of power. In comparison, our GME IP can be integrated into the existing licensing arrangements, as we continuedprocessor chip or chipset with no additional stand-alone IC required. Our proprietary platform software enables the compilation of TCAM images into graphs for GME processing utilizing a wider range of memory types including DRAM.

We believe the technology will generate new opportunities that require less up-front architectural changes by system designers and provide a scalable capacity and performance roadmap of options using our Accelerator Engine ICs. We began pursuing license opportunities for our VAE products in 2020 and expect to perform and deliver under outstanding license agreements and collect royalties from 1T- SRAM licensees. To date, we have completed our performance obligations under our existing licensing agreements, and we expect licensing and royalty revenues to be minimalbegin achieving production licenses for these products in future years.2021.

Risk Factors

An investment in our common stocksecurities is risky. Prior to making a decision about investing in our common stock,securities, you should carefully consider the specific risks discussed in our other filings with the SEC, which are incorporated by reference in this prospectus, together with all of the other information contained in this prospectus, any applicable prospectus supplement, or otherwise incorporated by reference in this prospectus. The risks and uncertainties described in our SEC filings are not the only ones facing us. Additional risks and uncertainties not presently known to us, or that we currently see as immaterial, may also harm our business. If any of the risks or uncertainties described in the applicable prospectus supplement or our SEC filings or any such additional risks and uncertainties actually occur, our business, results of operations, cash flows and financial condition could be materially and adversely affected. In that case, the trading price of our common stocksecurities could decline, and you might lose part or all of your investment.

Use of Proceeds

We intend to use the net proceeds for working capital, and other general corporate purposes.purposes (including research and development and sales and marketing, and capital expenditures) and in furtherance of our corporate strategy, which may include investing in, acquiring businesses or technologies, or other strategic transactions to facilitate our long term growth, increase our revenues, and enhance our technology and product offerings. We have not entered into any definitive agreements with respect to any acquisitions or other

strategic transactions as of the date of this prospectus supplement. However, the amount and timing of what we actually spend for these purposes may vary and will depend on a number of factors, including our future revenue and cash generated by operations and the other factors described in “Risk Factors.” Accordingly, our management will have discretion and flexibility in applying the net proceeds of this offering. Pending use of the net proceeds as described above, we intend to invest the net proceeds in money market funds and investment-grade debt securities.

The amounts we plan to spend on each area of our operations, including capital expenditures, as well as the timing of any expenditures, are determined by internal planning and budgeting processes, and may change over time. Pending such uses, the net proceeds of this offering will be invested according to a cash management policy adopted by our board of directors and focused on preservation of capital.

Dilution

We will set forth in a prospectus supplement the following information regarding any material dilution of the equity interests of investors purchasing securities sold by us in a primary offering under this prospectus:

General Description of Securities That We May Sell

We may offer and sell, at any time and from time to time:

The terms of any securities we offer will be determined at the time of sale. When particular securities are offered, a supplement to this prospectus will be filed with the SEC, which will describe the terms of the offering and sale of the offered securities.

Description of Capital Stock

General

The following description of our capital stock and provisions of our certificate of incorporation and bylaws is a summary only and not a complete description.

Our authorized capital stock consists of 120,000,000 shares of common stock, par value $0.001 per share, and 20,000,000 shares of preferred stock, par value $0.01 per share.

Common Stock

As of October 1, 2017, 8,002,010At June 30, 2021, 8,660,382 shares of our common stock were outstanding and held of record by 16five stockholders. The actual number of stockholders is significantly greater than this number of record stockholders and includes stockholders who are beneficial owners but whose shares are held in street name by brokers and other nominees. This number of stockholders of record also does not include stockholders whose shares may be held in trust by other entities.

Each holder of our common stock is entitled to—to:

Holders of common stock have no cumulative voting rights, redemption rights or preemptive rights to purchase or subscribe for any shares of our common stock or other securities. All of the outstanding shares of common stock are fully paid and nonassessable.  The rights, preferences and privileges of holders of our common stock are subject to, and may be adversely affected by, the rights of the holders of shares of any series of preferred stock that we may designate and issue in the futurefuture.

Preferred Stock

We have designated 120,000 shares of our preferred stock as Series AA preferred stock for issuance pursuant to the exercise of rights under our rights plan, none of which are outstanding. For more information on the rights plan, see the discussion below. We have no current intention to issue any other shares of preferred stock.

Our board of directors has the authority, subject to any limitations prescribed by Delaware law, to issue shares of preferred stock in one or more series and to fix and determine the relative rights and preferences of the shares constituting any series to be established, without any further vote or action by the stockholders. Any shares of our preferred stock so issued may have priority over our common stock with respect to dividend, liquidation and other rights.

Our board of directors may authorize the issuance of our preferred stock with voting or conversion rights that could adversely affect the voting power or other rights of the holders of our common stock. Although the issuance of our preferred stock could provide us with flexibility in connection with possible acquisitions and other corporate purposes, under some circumstances, it could have the effect of delaying, deferring or preventing a change of control.

Antitakeover Effects of Provisions of Our Certificate of Incorporation and Bylaws and of Delaware Law.Law

Certain provisions of our charter documents and Delaware law could have an anti-takeover effect and could delay, discourage or prevent a tender offer or takeover attempt that a stockholder might consider to be in its best interests, including attempts that might otherwise result in a premium being paid over the market price of our common stock.

Certificate of Incorporation and Bylaws.  Our certificate of incorporation provides that stockholders can take action only at a duly called annual or special meeting of the stockholders and not by written consent. At the same time, our bylaws

provide that special meetings of stockholders may be called only by our chairman of the board, our chief executive officer, a majority of the total number of authorized directors or any individual holder of 25% of the outstanding shares of common stock. These provisions could delay consideration of a stockholder proposal until the next annual meeting. Our bylaws provide for an advance notice procedure for the nomination, other than by or at the direction of our board of directors, of candidates for election as directors, as well as for other stockholder proposals to be considered at annual meetings of stockholders.  In addition, under our bylaws newly created directorships resulting from any increase in the number of directors or any vacancies in the board resulting from death, resignation, retirement, disqualification, removal from office or other cause during a director’s term in office can be filled by the vote of the remaining directors in office, and the board is expressly authorized to amend the bylaws without stockholder consent. These provisions may preclude a third party from removing incumbent directors and can control of our board of directors. Accordingly, these provisions could discourage a third party from initiating a proxy contest, making a tender offer or otherwise attempting to gain control of our company.

Delaware TakeoverAnti-Takeover Statute.  Section 203 of the Delaware General Corporation Law, or DGCL, generally prohibits a publicly-held Delaware corporation from engaging in an acquisition, asset sale or other transaction resulting in a financial benefit to any person who, together with affiliates and associates, owns, or within three years did own, 15.0% or more of a corporation’s voting stock. The prohibition continues for a period of three years after the date of the transaction in which the person becomes an owner of 15.0% or more of the corporation’s voting stock, unless the business combination is approved in a prescribed manner. The statute could prohibit, delay, defer or prevent a change in control with respect to our company.

Antitakeover EffectsMarket-Making, Stabilization and Other Transactions

There is currently no market for any of Our Rights Plan

On November 10, 2010, we executed a rights agreement in connection with the declaration by our board of directors of a dividend of one preferred stock purchase right to be paid on November 10, 2010, referred to as the "record date," for each share ofoffered securities, other than our common stock issued and outstanding atwhich is traded on Nasdaq.  If the close of business on the record date. Each right entitles the registered holder to purchase one one-thousandth of a share of our Series AA Preferred Stock, $0.01 par value per share,offered securities are traded after their initial issuance, they may trade at a discount from their initial offering price, of $48.00 per one one-thousandth ofdepending upon prevailing interest rates, the market for similar securities and other factors.  While it is possible that an underwriter could inform us that it intends to make a share ofmarket in the offered securities, any such Series AA Preferred Stock, subjectunderwriter would not be obligated to adjustment, includingdo so, and any such market-making could be discontinued at any time without notice.  Therefore, no assurance can be given as a result ofto whether an active trading market will develop for the offered securities.  We have no current plans for listing the preferred stock, warrants or subscription rights on any securities

exchange or quotation system.  Any such listing with respect to our one-for-ten reversepreferred stock, split in February 2017 (which adjustment is not reflected here). Thewarrants or subscription rights will not be exercisable until a third party acquires 15% of our common stockdescribed in the applicable prospectus supplement or commences or announces its intent to commence a tender offer for at least 15% of our common stock, other than holders of "grandfathered stock"offering materials, as defined below.

"Grandfathered stock" refers to stock held by Carl E. Berg, formerly a member of our board of directors for approximately 20 years, and his affiliates. The beneficial ownership threshold for a holder of grandfathered stock is 20%, rather than 15%. In addition, under the rights agreement, the firm of Ingalls & Snyder, or I&S, and its managed account beneficial owners collectively will not trigger the rights as long as none of their shares are held for the purpose of acquiring control or effecting change or influence in control of us. This exclusion applies only to shares of common stock for which there is only shared dispositive power and I&S has only non-discretionary voting power.

The rights agreement could delay, deter or prevent an investor from acquiring us in a transaction that could otherwise result in our stockholders receiving a premium over the market price for their shares of common stock.case may be.

Transfer Agent

The transfer agent and registrar for our common stock is Wells Fargo Bank, National Association.Equiniti Trust Company.

Description of Warrants

The following description, together with the additional information we include in any applicable prospectus supplement, summarizes the material terms and provisions of the warrants that we may offer under this prospectus and any related warrant agreements and warrant certificates. While the terms we have summarized below will apply generally to any warrants we may offer, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement, which may differ from the terms we describe below.

General

We may issue, together with other securities or separately, warrants to purchase shares of our common stock or our preferred stock. We may issue the warrants directly to the purchasers of the warrants or under warrant agreements to be entered into between us and a bank or trust company, as warrant agent, all as set forth in the applicable prospectus supplement. A warrant agent will act solely as our agent in connection with the warrants of the series being offered and will not assume any obligation or relationship of agency or trust for or with any holders or beneficial owners of warrants.

The prospectus supplement will describe the following terms, where applicable, of warrants that we may offer:

Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including the right to receive dividends, if any, or payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Exercise of Warrants

Each warrant will entitle the holder thereof to purchase for cash the number of shares of common stock or preferred stock at the exercise price as will in each case be set forth in, or be determinable as set forth in, the applicable prospectus supplement. Warrants may be exercised at any time up to the close of business on the expiration date set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

Warrants may be exercised as set forth in the applicable prospectus supplement relating to the warrants offered thereby. Upon receipt of payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will, as soon as practicable, forward the purchased securities. If less than all of the warrants represented by the warrant certificate are exercised, a new warrant certificate will be issued for the remaining warrants.

Enforceability of Rights of Holders of Warrants

Each warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, that holder’s warrants.

Description of Units

We may, from time to time, issue units comprised of one or more of the other securities described in this prospectus in any combination. A prospectus supplement will describe the specific terms of the units offered under that prospectus supplement, and any special considerations applicable to investing in those units. You must look at the applicable prospectus supplement and any applicable unit agreement for a full understanding of the specific terms of any units. We will incorporate by reference into the registration statement of which this prospectus is a part the form of unit agreement, including a form of unit certificate, if any, that describes the terms of the series of units we are offering before the issuance of the related series of units. While the terms we have summarized below will generally apply to any future units that we may offer under this prospectus, we will describe the particular terms of any series of units that we may offer in more detail in the applicable prospectus supplement and incorporated documents. The terms of any units offered under a prospectus supplement may differ from the terms described below. 

General

We may issue units consisting of common stock, preferred stock, warrants or any combination thereof in such amounts and in such numerous distinct series as we determine. Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each included security. The unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately, at any time, or at any time before a specified date.

We will describe in the applicable prospectus supplement and any incorporated documents the terms of the series of units, including the following:

The provisions described in this section, as well as those described under “Description of Capital Stock - Common Stock,” “Description of Capital Stock - Preferred Stock” and “Description of Warrants” will apply to each unit and to any common stock, preferred stock or warrant included in each unit, respectively.

Enforceability of Rights by Holders of Units

Each unit agent will act solely as our agent under the applicable unit agreement and will not assume any obligation or relationship of agency or trust with any holder of any unit. A single bank or trust company may act as unit agent for more than one series of units. A unit agent will have no duty or responsibility in case of any default by us under the applicable unit agreement or unit, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a unit, without the consent of the related unit agent or the holder of any other unit, may enforce by appropriate legal action its rights as holder under any security included in the unit.

Title

We, the unit agent, and any of their agents may treat the registered holder of any unit certificate as an absolute owner of the units evidenced by that certificate for any purposes and as the person entitled to exercise the rights attaching to the units so requested, despite any notice to the contrary.

Description of Subscription Rights

We may issue subscription rights to purchase shares of our common stock, preferred stock or warrants. These subscription rights may be issued independently or together with any other security offered hereby and may or may not be transferable by the stockholder receiving the subscription rights in such offering.  In connection with any offering of subscription rights, we may enter into a standby arrangement with one or more underwriters or other purchasers pursuant to which the underwriters or other purchasers may be required to purchase any securities remaining unsubscribed for after such offering.

The applicable prospectus supplement will describe the specific terms of any offering of subscription rights for which this prospectus is being delivered, including the following:

The description in the applicable prospectus supplement of any subscription rights we offer will not necessarily be complete and will be qualified in its entirety by reference to the applicable subscription rights certificate, which will be filed with the SEC, if we offer subscription rights.

Plan of Distribution

We may sell the securities in and outside the United States through underwriters or dealers, directly to purchasers, including our affiliates, through agents, or through a combination of any of these methods. The prospectus supplement will include the following information:

Sale through Underwriters or Dealers

If underwriters are used in the sale of any of these securities, the underwriters will acquire the securities for their own account. The underwriters may resell the securities from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. Underwriters may offer securities to the public either through underwriting syndicates represented by one or more managing underwriters or directly by one or more firms acting as underwriters. Unless we inform you otherwise in any prospectus supplement, the obligations of the underwriters to purchase the securities will be subject to certain conditions, and the underwriters will

be obligated to purchase all the offered securities if they purchase any of them. The underwriters may change from time to time any public offering price and any discounts or concessions allowed or reallowed or paid to dealers.

During and after an offering through underwriters, the underwriters may purchase and sell the securities in the open market. These transactions may include overallotment and stabilizing transactions and purchases to cover syndicate short positions created in connection with the offering. The underwriters may also impose a penalty bid, which means that selling concessions allowed to syndicate members or other broker-dealers for the offered securities sold for their account may be reclaimed by the syndicate if the offered securities are repurchased by the syndicate in stabilizing or covering transactions. These activities may stabilize, maintain or otherwise affect the market price of the offered securities, which may be higher than the price that might otherwise prevail in the open market. If commenced, the underwriters may discontinue these activities at any time.

Some or all of the securities that we offer though this prospectus may be new issues of securities with no established trading market. Any underwriters to whom we sell these securities for public offering and sale may make a market in those securities, but they will not be obligated to and they may discontinue any market making at any time without notice. Accordingly, we cannot assure you of the liquidity of, or continued trading markets for, any securities that we offer.

If dealers are used in the sale of securities, we will sell the securities to them as principals. They may then resell those securities to the public at varying prices determined by the dealers at the time of resale. We will include in the prospectus supplement the names of the dealers and the terms of the transaction.

Direct Sales and Sales through Agents

We may sell the securities directly, and not through underwriters or agents. We may also sell the securities through agents designated from time to time. In the prospectus supplement, we will name any agent involved in the offer or sale of the offered securities, and we will describe any commissions payable to the agent. Unless we inform you otherwise in the prospectus supplement, any agent will agree to use its reasonable best efforts to solicit purchases for the period of its appointment.

We may sell the securities directly to institutional investors or others who may be deemed to be underwriters within the meaning of the Securities Act of 1933, as amended, or the Securities Act, with respect to any sale of those securities. We will describe the terms of any such sales in the prospectus supplement.

Issuance of Common Stock Pursuant to Certain Warrant Exercises

We may also offer and sell our common stock or preferred stock upon the exercise of warrants issued by us, pursuant to the exemption from the registration requirements provided by Section 3(a)(10) of the Securities Act, in connection with a settlement of litigation against us. No underwriter would be used in connection with such offer and sale of common stock or preferred stock or the exercise of

such warrants. We would issue the shares of our common stock or preferred stock directly to the holders of such warrants, upon the exercise of such warrants, from time to time. We will describe the terms of any such offers, sales and warrants in a prospectus supplement.

General Information

We may have agreements with the agents, dealers and underwriters to indemnify them against certain civil liabilities, including liabilities under the Securities Act, or to contribute with respect to payments that the agents, dealers or underwriters may be required to make. Agents, dealers and underwriters may be customers of, engage in transactions with or perform services for us in the ordinary course of their businesses.

ExpertsExperts

The consolidated financial statements of MoSys, Inc. as of December 31, 2016 and 20152020 and for each of the three years in the periodyear then ended December 31, 2016, incorporated in this Registration Statement on Form S‑3prospectus and elsewhere in the registration statement by reference to its

the Annual Report on Form 10‑K10-K for the year ended December 31, 2016,2020, have been so incorporated in reliance on the report (which containsof Weinberg & Company, P.A. an explanatory paragraph relatingindependent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

The consolidated financial statements of MoSys, Inc. as of December 31, 2019 and for the year then ended incorporated in this prospectus and elsewhere in the registration statement by reference to the Company’s ability to continue as a going concern as describedAnnual Report on Form 10-K for the year ended December 31, 2020, have been so incorporated in Note 1 toreliance on the consolidated financial statements)report of BPM LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

Legal Matters

The validity of the issuance of shares of any securities offered hereby will be passed upon for us by Pillsbury Winthrop Shaw PittmanMitchell Silberberg & Knupp LLP, Palo Alto, California.New York, New York.

Where You Can Find More Information

We file annual, quarterly and specialcurrent reports, proxy statements and other information with the SEC. In addition,Our SEC filings are available to the public at the SEC’s website at www.sec.gov. Our website is located at www.mosys.com. Through links on the “Investors” portion of our website, we havemake available free of charge all reports, any amendments to those reports and other information filed with, or furnished to, the SEC pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Such material is made available through our website as soon as reasonably practicable after we electronically file the information with, or furnish it to, the SEC. The information contained on or that can be accessed through our website does not constitute part of this prospectus, except for reports filed with the SEC that are specifically incorporated herein by reference.

This prospectus is part of a Registration Statementregistration statement on Form S‑3,S-3 that we filed with the SEC. This prospectus does not contain all of the information included in the registration statement. Forms of any indenture or other documents establishing the terms of the offered securities are filed as exhibits to the registration statement of which this prospectus isforms a part or will be filed through an amendment to our registration statement on Form S-3 or under the Securities Act, with respectcover of a Current Report on Form 8-K or other filed document and incorporated into this prospectus by reference. Statements in this prospectus about these documents are summaries and each statement is qualified in all respects by reference to the sharesdocument to which it refers. You should refer to the actual documents for a more complete description of common stock offered hereby. Youthe relevant matters. The full registration statement, including exhibits thereto, may read and obtain copies at prescribed rates of any document that we file withbe obtained from the SEC at its Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1‑800‑SEC‑0330 for further information on the operation of the Public Reference Room. Our SEC filings are also available to you free of charge at the SEC’s web site at http://www.sec.gov, which contains reports, proxy and information statements and other information regarding issuers that file electronically with the SEC.or us as indicated above.

Our common stock is traded on the Capital Market of the NASDAQ Stock Market. Material filed by us can be inspected at the offices of the Financial Industry Regulatory Authority, 1735 K Street, N.W., Washington, D.C. 20006.

Incorporation by Reference

The SEC allows us to “incorporate by reference” the information we file with them, which means that we can disclose important information by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC will automatically update and supersede the information that is either incorporated by reference, or contained in, this prospectus and will be considered a part of this prospectus from the date those documents are filed. We incorporate by reference the documents listed below:

(a)our Annual Report on Form 10‑K for the fiscal year ended December 31, 2016, filed with the SEC on March 30, 2017;

(b)our Current Report on Form 8‑K filed with the SEC on February 14, 2017;

(c)our Quarterly Report on Form 10‑Q for the three months ended March 31, 2017, filed with the SEC on May 12, 2017;

(d)our definitive proxy statement on Schedule 14A filed with the SEC on June 6, 2016;

(e)our Current Report on Form 8‑K filed with the SEC on June 30, 2017;

(f)our Quarterly Report on Form 10‑Q for the three and six months ended June 30, 2017, filed with the SEC on August 10, 2017;

(g)our Current Report on Form 8‑K filed with the SEC on October 2, 2017;

(h)our Current Report on Form 8‑K filed with the SEC on October 9, 2017; and

(i)the description of our capital stock set forth in our Registration Statement on Form 8‑A, filed with the SEC on June 26, 2001, as amended by Amendment No. 2 to Registration Statement on Form 8‑A/A, filed with the SEC on November 12, 2010, Amendment No. 3 on Form 8‑A/A, filed on July 27, 2011, and Amendment No. 4 on Form 8‑A/A, filed on May 24, 2012.