How to: Determine CPU Count
Microsoft SQL Server 2005 Express Edition is limited to running on a single CPU. This topic contains the following information:
How CPU count is determined for licensing
How CPUs are used during processing. This includes usage of multiple core CPUs and hyperthreaded CPUs
SQL Server Express can be installed on a computer that has more than one CPU, but it will use only one of the CPUs. When it determines the CPU count for the purpose of licensing, SQL Server Express counts only the physical processor chips in the computer. A single core CPU, a dual core CPU, and a hyperthreaded CPU are all considered to be a single CPU by SQL Server Express.
SQL Server Express does recognize the additional processors that are available when it is installed on a computer that has multiple core and hyperthreaded CPUs. A separate scheduler is started for each core in a multiple core CPU, and for each logical processor in a hyperthreaded CPU. For example, if you have a dual-core CPU, two separate schedulers are started by SQL Server Express and available for use. This lets SQL Server Express use a degree of parallel processing within the limits of the single CPU that is being used.