Many thanks for the feedback so far, and especially to h.berg for correcting my misunderstanding with regard to thread execution.

It's interesting that you mention "...less context switching because more CPU threads are available..." because the increase in the number of threads actually seems quite small. E.g. a quad-core processor with and without HT will have 288 and 256 worker threads respectively (on 32-bit) -- so actually significantly fewer threads per scheduler. Jonathan Kehayias [/url]has written quite extensively on this topic, and it's resulting "thread contention" that, as you observe, can cause you trouble if you have HT enabled and a lot of long-running queries in your workload.

Cheers,

Tony.