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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0000901719-08-000013.txt : 20080221
<SEC-HEADER>0000901719-08-000013.hdr.sgml : 20080221
<ACCEPTANCE-DATETIME>20080221163446
ACCESSION NUMBER:		0000901719-08-000013
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080219
FILED AS OF DATE:		20080221
DATE AS OF CHANGE:		20080221

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MoSys, Inc.
		CENTRAL INDEX KEY:			0000890394
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				770291941
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		755 N MATIHILDA AVENUE
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94085
		BUSINESS PHONE:		408 731 1800

	MAIL ADDRESS:	
		STREET 1:		755 N MATIHILDA AVENUE
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94085

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MONOLITHIC SYSTEM TECHNOLOGY INC
		DATE OF NAME CHANGE:	19960613

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BERG CARL E
		CENTRAL INDEX KEY:			0000901719
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-32929
		FILM NUMBER:		08633316

	BUSINESS ADDRESS:	
		STREET 1:		BERG & BERG DEVELOPERS
		STREET 2:		10050 BANDLEY DRIVE
		CITY:			CUPERTINO
		STATE:			CA
		ZIP:			95014
		BUSINESS PHONE:		4087250700

	MAIL ADDRESS:	
		STREET 1:		C/O BERG & BERG DEVELOPERS
		STREET 2:		10050 BANDLEY DR
		CITY:			CUPERTINO
		STATE:			CA
		ZIP:			95014
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-02-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000890394</issuerCik>
        <issuerName>MoSys, Inc.</issuerName>
        <issuerTradingSymbol>MOSY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000901719</rptOwnerCik>
            <rptOwnerName>BERG CARL E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BERG &amp; BERG DEVELOPERS</rptOwnerStreet1>
            <rptOwnerStreet2>10050 BANDLEY DR</rptOwnerStreet2>
            <rptOwnerCity>CUPERTINO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95014</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>COMMON STOCK</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2008-02-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>3.7939</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100200</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>COMMON STOCK</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>124998</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>COMMON STOCK</value>
                <footnoteId id="F3"/>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>169998</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">THESE SECURITIES ARE OWNED BY CARL E. BERG, THE DESIGNATED BENEFICIAL OWNER FOR THE REPORTING GROUP.  THE DESIGNATED BENEFICIAL OWNER DISCLAIMS BENEFICIAL OWNERSHIP EXCEPT TO THE EXTENT OF HIS PECUNIARY INTERESTS THEREIN.</footnote>
        <footnote id="F2">THESE SECURITIES ARE OWNED BY BERG &amp; BERG ENTERPRISES, LLC (&quot;BB&quot;), A MEMBER OF THE REPORTING GROUP.  THE DESIGNATED BENEFICIAL OWNER DISCLAIMS BENEFICIAL OWNERSHIP EXCEPT TO THE EXTENT OF THEIR RESPECTIVE PECUNIARY INTERESTS THEREIN.</footnote>
        <footnote id="F3">THESE SECURITIES ARE OWNED BY MARY ANN BERG, THE WIFE OF THE DESIGNATED BENEFICIAL OWNER.  CARL BERG DISCLAIMS BENEFICIAL OWNERSHIP OF THE 169,998 SHARES HELD BY HIS WIFE AS HE HAS NO ECONOMIC INTEREST IN ANY OF THESE SHARES.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>CARL E. BERG, AS AN INDIVIDUAL AND AS MANAGER OF BB</signatureName>
        <signatureDate>2008-02-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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