Can hyperthreading be disabled after installing Windows?

Question

I have a PowerEdge 1950 with 2 dual-core processors.  I'm running Windows 2003 Web Edition, and SQL Express Edition 2005.   When I view the processors, I see 8, and figured out that hyperthreading it turned on: BIOS -> LOGICAL CPU = ENABLED. I tried to disable this, and Windows 2003 Web Edition would no longer boot, and I was forced to 'repair' install Windows 2003 Web Edition again.   I don't believe IIS and SQL Express 2005 utilize hyperthreading, so I think it should be turned off, correct?  I worry that it is partitioning my processors and only making '1/8th' of my total processing power available.  Currently, when I run large queries, only 1 of the 8 processors appears to be utilized (according to Windows 2003 Task Manager / Performance tab).   Is there a way to turn hyperthreading off that doesn't require me to completely re-intall Windows 2003 Web Edition?   Thank you! Darin Spence darin_spence@hotmail.com

paulsilverstein · Answer

Windows 2003 and since SQL 2000 SP4 (I think) has support for hyperthreading, so you should be fine.   As for turning it off, I have recently turned off hyperthreading on a couple machines running 2000 and 2003, and SQL 2000 and everything booted up just dandy afterwards.

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