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Probably this would be the answer to your question <a href="http://msdn.microsoft.com/en-us/library/ms143760.aspx" rel="ugc nofollow">http://msdn.microsoft.com/en-us/library/ms143760.aspx</a>
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Probably this would be the answer to your question http://msdn.microsoft.com/en-us/library/ms143760.aspx [http://msdn.microsoft.com/en-us/library/ms143760.aspx]

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The above post is for SQL 2008. See this for SQL 2005 <a href="http://msdn.microsoft.com/en-us/library/ms143760(SQL.90).aspx" rel="ugc">http://msdn.microsoft.com/en-us/library/ms143760(SQL.90).aspx</a>.
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The above post is for SQL 2008. See this for SQL 2005 http://msdn.microsoft.com/en-us/library/ms143760(SQL.90).aspx [http://msdn.microsoft.com/en-us/library/ms143760(SQL.90).aspx].

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Thank you, but why do you think it is 4 cores, not 4 sockets as for operating system? 
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Thank you, but why do you think it is 4 cores, not 4 sockets as for operating system?

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We have the same OS, same application and same SQL Server running on 2 very simlar machines:<br />
Windows Server 2003 R2 x64<br />
MS SQL Server 2005 Standard x64<br />
Dell PowerEdge 2900 (differ in number of processors)<br />
On PE2900 with 2 dual-core processors (4 cores) SQL Server uses all 4 cores<br />
On PE2900 with 4 dual-core processors (8 cores) SQL Server uses ONLY 2 CORES!<br />
Can anyone tell why and how to make the latter use all 8 cores?
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We have the same OS, same application and same SQL Server running on 2 very simlar machines:
Windows Server 2003 R2 x64
MS SQL Server 2005 Standard x64
Dell PowerEdge 2900 (differ in number of processors)
On PE2900 with 2 dual-core processors (4 cores) SQL Server uses all 4 cores
On PE2900 with 4 dual-core processors (8 cores) SQL Server uses ONLY 2 CORES!
Can anyone tell why and how to make the latter use all 8 cores?

Using all processor cores with WS 2003 Standard x64 and SQL Server

The Microsoft Legacy Operating System topic includes legacy versions of Microsoft operating systems prior to Windows 2000: All versions of MS-DOS and other versions developed for specific manufacturers and Windows 3/3.1, Windows 95 and Windows 98, plus any other Windows-related versions, and Windows Mobile.

Microsoft Legacy OS

The Microsoft Server topic includes all of the legacy versions of the operating system, including the Windows NT 3.1, NT 3.5, NT 4.0 and Windows 2000 and Windows Home Server versions.

Microsoft Server OS

Windows Server 2003 was based on Windows XP and was released in four editions: Web, Standard, Enterprise and Datacenter. It also had derivative versions for clusters, storage and Microsoft’s Small Business Server. Important upgrades included integrating Internet Information Services (IIS), improvements to Active Directory (AD) and Group Policy (GP), and the migration to Automated System Recovery (ASR).