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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>0001104659-08-061928.txt : 20081003
<SEC-HEADER>0001104659-08-061928.hdr.sgml : 20081003
<ACCEPTANCE-DATETIME>20081003170140
ACCESSION NUMBER:		0001104659-08-061928
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20081001
FILED AS OF DATE:		20081003
DATE AS OF CHANGE:		20081003

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			NATIONAL SEMICONDUCTOR CORP
		CENTRAL INDEX KEY:			0000070530
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				952095071
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0525

	BUSINESS ADDRESS:	
		STREET 1:		2900 SEMICONDUCTOR DR
		STREET 2:		PO BOX 58090
		CITY:			SANTA CLARA
		STATE:			CA
		ZIP:			95052-8090
		BUSINESS PHONE:		4087215000

	MAIL ADDRESS:	
		STREET 1:		2900 SEMICONDUCTOR DR
		CITY:			SANTA CLARA
		STATE:			CA
		ZIP:			95052-8090

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			RELATIONAL INVESTORS LLC
		CENTRAL INDEX KEY:			0001047644
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0131

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-06453
		FILM NUMBER:		081107275

	BUSINESS ADDRESS:	
		STREET 1:		12400 HIGH BLUFF DRIVE
		STREET 2:		SUITE 600
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92130
		BUSINESS PHONE:		858.704.3333

	MAIL ADDRESS:	
		STREET 1:		12400 HIGH BLUFF DRIVE
		STREET 2:		SUITE 600
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92130

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WHITWORTH RALPH V
		CENTRAL INDEX KEY:			0001052622

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-06453
		FILM NUMBER:		081107274

	BUSINESS ADDRESS:	
		STREET 1:		4330 LAJOLLA VILLAGE DRIVE
		STREET 2:		SUITE 220
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92122
		BUSINESS PHONE:		858.704.3333

	MAIL ADDRESS:	
		STREET 1:		RELATIONAL INVESTORS LLC
		STREET 2:		12400 HIGH BLUFF DRIVE, SUITE 600
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92130

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			BATCHELDER DAVID H
		CENTRAL INDEX KEY:			0000947324

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-06453
		FILM NUMBER:		081107273

	BUSINESS ADDRESS:	
		STREET 1:		BATCHELDER & PARTNERS INC
		STREET 2:		4330 LA JOLLA VILLAGE DR STE 200
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92122
		BUSINESS PHONE:		858.704.3333

	MAIL ADDRESS:	
		STREET 1:		RELATIONAL INVESTORS LLC
		STREET 2:		12400 HIGH BLUFF DRIVE. SUITE 600
		CITY:			SAN DIEGO
		STATE:			CA
		ZIP:			92130
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>a4.xml
<DESCRIPTION>4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-10-01</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000070530</issuerCik>
        <issuerName>NATIONAL SEMICONDUCTOR CORP</issuerName>
        <issuerTradingSymbol>NSM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001047644</rptOwnerCik>
            <rptOwnerName>RELATIONAL INVESTORS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12400 HIGH BLUFF DRIVE, SUITE 600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92130</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001052622</rptOwnerCik>
            <rptOwnerName>WHITWORTH RALPH V</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12400 HIGH BLUFF DRIVE, SUITE 600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92130</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000947324</rptOwnerCik>
            <rptOwnerName>BATCHELDER DAVID H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>12400 HIGH BLUFF DRIVE, SUITE 600</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN DIEGO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92130</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2008-10-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>143068</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>16.80</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>33443949</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Through Limited Partnerships and managed accounts managed by reporting persons</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Relational Investors, LLC, is the sole general partner of Relational Investors, L.P., Relational Fund Partners, L.P., Relational Coast Partners, L.P., Relational Partners, L.P., RH Fund 1, L.P., RH Fund 4, L.P., RH Fund 6, L.P., RH Fund 7, L.P., Relational Investors VIII, L.P., Relational Investors IX, L.P., Relational Investors XI, L.P., Relational Investors XV, L.P., Relational Investors XVI, L.P. and the sole managing member of Relational Asset Management LLC and Relational Investors X GP LLC which serve as the sole general partners of Relational Investors III, L.P. and Relational Investors X, L.P., respectively.</footnote>
        <footnote id="F2">These Limited Partnerships own a total of 28,839,724 shares.  An additional 4,604,225 shares are held in accounts managed by Relational Investors, LLC.  All shares are owned indirectly by Relational Investors, LLC, and by Ralph V. Whitworth and David H. Batchelder (each of which is a reporting person hereunder), principals of Relational Investors, LLC.   The reporting persons disclaim beneficial ownership of these securities except to the extent of their pecuniary interest therein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Relational Investors LLC By: /s/ Ralph V. Whitworth, Principal</signatureName>
        <signatureDate>2008-10-03</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Ralph V. Whitworth</signatureName>
        <signatureDate>2008-10-03</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ David H. Batchelder</signatureName>
        <signatureDate>2008-10-03</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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