Having installed SQL Server 2005 x64 (with the latest patches) on a Windows
2008 server which is physically a single processor Intel x5570 Nehalam cpu
box (with 6GB ram), I find that when a CPU bound query schedules on anything
other then core 0 it takes twice the time to complete.

I have disabled HyperThreading and done extensive testing using the affinity
masks to ensure that this is always the case (cores 1,2 and 3 always take
twice as long as core 0 for a CPU bound query - not executing in parallel)

Is this a known issue? As the only way to make the system run quickly is to
only allow core 0 with the affinity mask, which obviously won't scale well.

Is there anything I can do to sort this out?
Many thanks