-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 J97ySxA0ti47k8dOHeZekbHdEm2yDx4qiGNjMAGxDWusfL2u96gMJ35qWjQVQ/ZA
 ZKjbZhlIyJjlSrjs4tatQA==

<SEC-DOCUMENT>0001424422-08-000009.txt : 20080725
<SEC-HEADER>0001424422-08-000009.hdr.sgml : 20080725
<ACCEPTANCE-DATETIME>20080725181702
ACCESSION NUMBER:		0001424422-08-000009
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		2
CONFORMED PERIOD OF REPORT:	20080724
FILED AS OF DATE:		20080725
DATE AS OF CHANGE:		20080725

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Kupec James D
		CENTRAL INDEX KEY:			0001300569

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-32929
		FILM NUMBER:		08971669

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		408 250 7196

	MAIL ADDRESS:	
		STREET 1:		145 SPYGLASS LANE
		CITY:			HALF MOON BAY
		STATE:			CA
		ZIP:			94109

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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-07-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001300569</rptOwnerCik>
            <rptOwnerName>Kupec James D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MOSYS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>755 N. MATHILDA AVENUE, SUITE 100</rptOwnerStreet2>
            <rptOwnerCity>SUNNYVALE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94085</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Option to purchase common stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>4.14</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2008-07-24</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2008-08-24</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-07-24</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>160000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Options vest at a rate of 8.333% per month</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ James Kupec</signatureName>
        <signatureDate>2008-07-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-24
<SEQUENCE>2
<FILENAME>poa_kupec4-2txt.txt
<DESCRIPTION>POWER OF ATTORNEY
<TEXT>
POWER OF ATTORNEY

      The undersigned, as a Section 16 reporting person of MoSys, Inc.
 (the 'Company'), hereby constitutes and appoints Joyce Goto and Jim Sullivan
, and each of them, the undersigned's true and lawful attorney-in-fact to:

1.	complete and execute Forms 3, 4 and 5 and other forms and all
amendments thereto as such attorney-in-fact shall in his or her discretion
determine to be required or advisable pursuant to Section 16 of the Securities
Exchange Act of 1934 (as amended) and the rules and regulations promulgated
thereunder, or any successor laws and regulations, as a consequence of the
undersigned's ownership, acquisition or disposition of securities of the
Company; and

2.	do all acts necessary in order to file such forms with the Securities
and Exchange Commission, any securities exchange or national association, the
Company and such other person or agency as the attorney-in-fact shall deem
appropriate.

      The undersigned hereby ratifies and confirms all that said attorneys
- -in-fact and agents shall do or cause to be done by virtue hereof.  The
undersigned acknowledges that the foregoing attorneys-in-fact, in serving
in such capacity at the request of the undersigned, are not assuming, nor
is the Company assuming, any of the undersigned's responsibilities to comply
with Section 16 of the Securities Exchange Act of 1934 (as amended).

      This Power of Attorney revokes all previous powers of attorney granted
by the undersigned for the purposes specified above and shall remain in full
force and effect until the undersigned is no longer required to file Forms
3, 4, and 5 with respect to the undersigned's holdings of and transactions
in securities issued by the Company, unless earlier revoked by the undersigned
in a signed writing delivered to the Company and the foregoing attorneys
- -in-fact.

      IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney
to be executed as of this _____24th_______ day of
July____________________, __2008___.


Signature: /s/ James Kupec

Print Name: James Kupec

</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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