Re: Intel Hyper-threading -- pointless on the desktop?

From: R. McCarty (PCEngWork-NoSpam__at_mindspring.com)
Date: 03/29/04 

Date: Mon, 29 Mar 2004 20:28:08 GMT

1. Yes, If HT is enabled in BIOS before XP installs, then
     it will load the Multiprocessor HAL. However, if you
     subsequently disable HT in BIOS the XP HAL will
     still function but without the Hyperthreading. TaskMgr
     will only display the single processor states.

     So essentially, both BIOS HT must be enabled and
     the MP HAL must be in place for HT to work.

2. No, once a HAL is in place changing BIOS settings
    will not cause the Computer driver (HAL) to be
    automatically changed out. You can downstep from
    Multiprocessor to ACPI HAL by changing the driver.
    But this only works one-way. You can't change an
    ACPI HAL back to Multiprocessor without doing a
    "Repair" install of XP. (At least I've never tried to
     switch the driver from ACPI back to an MP)

Hyperthreading is application dependant, I believe Office &
several other programs make use of it. In my case I did a
PCPitstop benchmark with & without HT and the total score
did not vary but a few points (~1500).
 I'm not sure to what extent XP makes use of HT if any at
all.

"user1" <anonymous@discussions.microsoft.com> wrote in message
news:20C48F21-7730-431A-B813-5D55EA0BC568@microsoft.com...
> R.McCarthy,
> you wrote :"I have a HT processor. I can tell you that the difference in
> overall performance between using HT and a Multiprocessor
> HAL and disabling it and using the ACPI Hal is around 2%.
> Some gaming/tweaking sites will recommend that you turn
> it off and use the ACPI HAL, but I don't recommend users
> disable HT'ing."
>
> I am wrestingling with this issue so I want to ask about your response
> cited above.
> 1) regardless of how you installed XP, are you suggesting that a HT
> enabled system NEEDs or demands a MP HAL and therefore installs on during
> the XP setup process?
> 2.) Are you suggesting that disabling HT in the bios in a HT enabled
> systme will cause windows to simply change the MP HAL to ACPI HAL on the
> next start up?
> Please advise. I'd be very interested in your experience. please look....
> higgs_field at bell south(one word) .net Thanks...
>

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