Multi-processor support in Microsoft Windows Small Business Server 2003

[Today’s post comes to us courtesy of Justin Crosby]

We sometimes get asked how many processors SBS 2003 supports.  Microsoft Windows Small Business Server 2003 supports 2 physical processors.  These processors can be single-core, multi-core, or hyper threaded.   Using a multi-core or hyper threaded processor you will see more than 2 logical processors.  This will result in the following warning when running SBS 2003 setup:


If you get this error and you have two physical processors or less, all you need to do is click “I acknowledge all warnings” and click next.

 SBS 2003 does not have a limit on logical processors.  For example if you have 2 quad-core processors (without hyper threading) you will see 8 logical processors inside Windows.  SBS will utilize all of your logical processors.  Here are some screen shots from a recent test we performed with two quad-core processors:



If you have the premium version of SBS 2003 and plan on installing ISA 2004 please have a copy of ISA 2004 SP3 or SP2 available when you begin the install.  There is an issue with the pre-SP1 version of ISA 2004 where certain ISA 2004 services (ISACTRL and WSPSRV) would not start on a multiprocessor computer.  For more information on this issue please see:

Please note that just because your operating system supports multiple processors it does not mean that your applications will fully utilize them.  The application must be designed to support multiple processors.  For more information on a specific application please contact that application’s vendor.