Turning Hyperthreading on/off with XP

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Can I reboot XP, turn hyperthreading on/off in the BIOS, boot back into XP
and XP with see that hyperthreading is either on/off and run accordingly? Or
are there other settings or things to take into consideration?
 
Can I reboot XP, turn hyperthreading on/off in the BIOS, boot
back into XP
and XP with see that hyperthreading is either on/off and run
accordingly? Or
are there other settings or things to take into consideration?
Click to expand...

You probably don;t want to do this, as windows XP (unpon instalation)
will have configured it’s self for two CPUs (Since when hyper
threading is enabled it treats them as two CPUs). So turning it off
with out reinstalling windows will probably result in system
instability in the best situation.
 
You can turn off Hyperthreading in the BIOS and the Multiprocessor
HAL will continue to work. However, if you installed with a "Single"
CPU HAL like ACPI (without Multiprocessor) and then turn on the
Hyperthreading in BIOS, XP will continue to see/use only a single CPU.
So it works one way and not the other.
 
R. McCarty said:
You can turn off Hyperthreading in the BIOS and the Multiprocessor
HAL will continue to work. However, if you installed with a "Single"
CPU HAL like ACPI (without Multiprocessor) and then turn on the
Hyperthreading in BIOS, XP will continue to see/use only a single CPU.
So it works one way and not the other.
Click to expand...

Some motherboards built in the last couple of years load the "ACPI
Uniprocessor PC", ACPI APIC UP HAL (Halaacpi.dll). This will switch back and
forth between Uniprocessor and Multiprocessor with no problems. I have
upgraded several Celerons to P4's and the correct HAL was loaded with no
user intervention.

http://support.microsoft.com/default.aspx?scid=kb;en-us;309283

Kerry
 
hello,
That's not actually correct.
When you install the machine, setup tries to make a detemination whether
the machine is PIC or APIC.
If the motherboard is multi-processor aware, it should install the APIC
hal, even with a single processor.
Enabling hyperthreading in the bios after the fact and rebooting should
autodetect the second processor and make any changes.
Enabling or disabling hyperthreading should not change the fact that the
motherboard is APIC.
As long as APIC is detected it should work properly.
Unless there is an option in the bios to change from PIC to APIC or from
APIC to PIC, enabling hyperthreading or disabling hyperthreading in the
bios should not prevent the OS from recognizing the changes.
However if HAL is forced during setup using the F5 key, then the
auto-update is disabled for future changes.
If setup does not correctly detect the motherboard as APIC, it will not
reflect the changes either.
Thanks,
Darrell Gorter[MSFT]

This posting is provided "AS IS" with no warranties, and confers no rights
--------------------
<From: "R. McCarty" <[email protected]>
<References: <[email protected]>
<[email protected]>
<[email protected]>
<Subject: Re: Turning Hyperthreading on/off with XP
<Date: Wed, 12 Oct 2005 20:07:10 -0400
<Lines: 37
<X-Priority: 3
<X-MSMail-Priority: Normal
<X-Newsreader: Microsoft Outlook Express 6.00.2900.2670
<X-RFC2646: Format=Flowed; Original
<X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670
<Message-ID: <[email protected]>
<Newsgroups: microsoft.public.windowsxp.general
<NNTP-Posting-Host: user-1120rc9.dsl.mindspring.com 66.32.109.137
<Path: TK2MSFTNGXA01.phx.gbl!TK2MSFTNGP08.phx.gbl!TK2MSFTNGP15.phx.gbl
<Xref: TK2MSFTNGXA01.phx.gbl microsoft.public.windowsxp.general:478862
<X-Tomcat-NG: microsoft.public.windowsxp.general
<
<You can turn off Hyperthreading in the BIOS and the Multiprocessor
<HAL will continue to work. However, if you installed with a "Single"
<CPU HAL like ACPI (without Multiprocessor) and then turn on the
<Hyperthreading in BIOS, XP will continue to see/use only a single CPU.
<So it works one way and not the other.
<
<<> O.K. :) That's 2 replies - one says I can do it, the other says I
can't.
<> :) Now what?
<>
<> "Sparda" wrote:
<>
<>> "" wrote:
<>> > Can I reboot XP, turn hyperthreading on/off in the BIOS, boot
<>> > back into XP
<>> > and XP with see that hyperthreading is either on/off and run
<>> > accordingly? Or
<>> > are there other settings or things to take into consideration?
<>>
<>> You probably don;t want to do this, as windows XP (unpon instalation)
<>> will have configured itâ?Ts self for two CPUs (Since when hyper
<>> threading is enabled it treats them as two CPUs). So turning it off
<>> with out reinstalling windows will probably result in system
<>> instability in the best situation.
<>>
<>> --
<>> Posted using the http://www.windowsforumz.com interface, at author's
<>> request
<>> Articles individually checked for conformance to usenet standards
<>> Topic URL:
<>>
http://www.windowsforumz.com/General-Discussion-Turning-Hyperthreading-XP-ft
opict431889.html
<>> Visit Topic URL to contact author (reg. req'd). Report abuse:
<>> http://www.windowsforumz.com/eform.php?p=1450217
<>>
<
<
<
 
I follow most of your explanation, except on the APIC ( Advanced Peripheral
Interface Controller. Changing the Hyperthreading support in BIOS wouldn't
affect that in any way - would it ? Doesn't an APIC simply extend the normal
IRQ range up to 23 ? No big issue, but on my Intel 865 ( ACPI Mult...HAL)
if I turn off Hyperthreading in BIOS the HAL stays the same on a boot back
into XP, doesn't change from Multi->Uni
Thanks for the info -

"Darrell Gorter[MSFT]" said:
hello,
That's not actually correct.
When you install the machine, setup tries to make a detemination whether
the machine is PIC or APIC.
If the motherboard is multi-processor aware, it should install the APIC
hal, even with a single processor.
Enabling hyperthreading in the bios after the fact and rebooting should
autodetect the second processor and make any changes.
Enabling or disabling hyperthreading should not change the fact that the
motherboard is APIC.
As long as APIC is detected it should work properly.
Unless there is an option in the bios to change from PIC to APIC or from
APIC to PIC, enabling hyperthreading or disabling hyperthreading in the
bios should not prevent the OS from recognizing the changes.
However if HAL is forced during setup using the F5 key, then the
auto-update is disabled for future changes.
If setup does not correctly detect the motherboard as APIC, it will not
reflect the changes either.
Thanks,
Darrell Gorter[MSFT]

This posting is provided "AS IS" with no warranties, and confers no rights
--------------------
<From: "R. McCarty" <[email protected]>
<References: <[email protected]>
<[email protected]>
<[email protected]>
<Subject: Re: Turning Hyperthreading on/off with XP
<Date: Wed, 12 Oct 2005 20:07:10 -0400
<Lines: 37
<X-Priority: 3
<X-MSMail-Priority: Normal
<X-Newsreader: Microsoft Outlook Express 6.00.2900.2670
<X-RFC2646: Format=Flowed; Original
<X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670
<Message-ID: <[email protected]>
<Newsgroups: microsoft.public.windowsxp.general
<NNTP-Posting-Host: user-1120rc9.dsl.mindspring.com 66.32.109.137
<Path: TK2MSFTNGXA01.phx.gbl!TK2MSFTNGP08.phx.gbl!TK2MSFTNGP15.phx.gbl
<Xref: TK2MSFTNGXA01.phx.gbl microsoft.public.windowsxp.general:478862
<X-Tomcat-NG: microsoft.public.windowsxp.general
<
<You can turn off Hyperthreading in the BIOS and the Multiprocessor
<HAL will continue to work. However, if you installed with a "Single"
<CPU HAL like ACPI (without Multiprocessor) and then turn on the
<Hyperthreading in BIOS, XP will continue to see/use only a single CPU.
<So it works one way and not the other.
<
<<> O.K. :) That's 2 replies - one says I can do it, the other says I
can't.
<> :) Now what?
<>
<> "Sparda" wrote:
<>
<>> "" wrote:
<>> > Can I reboot XP, turn hyperthreading on/off in the BIOS, boot
<>> > back into XP
<>> > and XP with see that hyperthreading is either on/off and run
<>> > accordingly? Or
<>> > are there other settings or things to take into consideration?
<>>
<>> You probably don;t want to do this, as windows XP (unpon instalation)
<>> will have configured itâ?Ts self for two CPUs (Since when hyper
<>> threading is enabled it treats them as two CPUs). So turning it off
<>> with out reinstalling windows will probably result in system
<>> instability in the best situation.
<>>
<>> --
<>> Posted using the http://www.windowsforumz.com interface, at author's
<>> request
<>> Articles individually checked for conformance to usenet standards
<>> Topic URL:
<>>
http://www.windowsforumz.com/General-Discussion-Turning-Hyperthreading-XP-ft
opict431889.html
<>> Visit Topic URL to contact author (reg. req'd). Report abuse:
<>> http://www.windowsforumz.com/eform.php?p=1450217
<>>
<
<
<
Click to expand...
 
Thanks guys.

"Darrell Gorter[MSFT]" said:
hello,
That's not actually correct.
When you install the machine, setup tries to make a detemination whether
the machine is PIC or APIC.
If the motherboard is multi-processor aware, it should install the APIC
hal, even with a single processor.
Enabling hyperthreading in the bios after the fact and rebooting should
autodetect the second processor and make any changes.
Enabling or disabling hyperthreading should not change the fact that the
motherboard is APIC.
As long as APIC is detected it should work properly.
Unless there is an option in the bios to change from PIC to APIC or from
APIC to PIC, enabling hyperthreading or disabling hyperthreading in the
bios should not prevent the OS from recognizing the changes.
However if HAL is forced during setup using the F5 key, then the
auto-update is disabled for future changes.
If setup does not correctly detect the motherboard as APIC, it will not
reflect the changes either.
Thanks,
Darrell Gorter[MSFT]

This posting is provided "AS IS" with no warranties, and confers no rights
--------------------
<From: "R. McCarty" <[email protected]>
<References: <[email protected]>
<[email protected]>
<[email protected]>
<Subject: Re: Turning Hyperthreading on/off with XP
<Date: Wed, 12 Oct 2005 20:07:10 -0400
<Lines: 37
<X-Priority: 3
<X-MSMail-Priority: Normal
<X-Newsreader: Microsoft Outlook Express 6.00.2900.2670
<X-RFC2646: Format=Flowed; Original
<X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670
<Message-ID: <[email protected]>
<Newsgroups: microsoft.public.windowsxp.general
<NNTP-Posting-Host: user-1120rc9.dsl.mindspring.com 66.32.109.137
<Path: TK2MSFTNGXA01.phx.gbl!TK2MSFTNGP08.phx.gbl!TK2MSFTNGP15.phx.gbl
<Xref: TK2MSFTNGXA01.phx.gbl microsoft.public.windowsxp.general:478862
<X-Tomcat-NG: microsoft.public.windowsxp.general
<
<You can turn off Hyperthreading in the BIOS and the Multiprocessor
<HAL will continue to work. However, if you installed with a "Single"
<CPU HAL like ACPI (without Multiprocessor) and then turn on the
<Hyperthreading in BIOS, XP will continue to see/use only a single CPU.
<So it works one way and not the other.
<
<<> O.K. :) That's 2 replies - one says I can do it, the other says I
can't.
<> :) Now what?
<>
<> "Sparda" wrote:
<>
<>> "" wrote:
<>> > Can I reboot XP, turn hyperthreading on/off in the BIOS, boot
<>> > back into XP
<>> > and XP with see that hyperthreading is either on/off and run
<>> > accordingly? Or
<>> > are there other settings or things to take into consideration?
<>>
<>> You probably don;t want to do this, as windows XP (unpon instalation)
<>> will have configured itâ?Ts self for two CPUs (Since when hyper
<>> threading is enabled it treats them as two CPUs). So turning it off
<>> with out reinstalling windows will probably result in system
<>> instability in the best situation.
<>>
<>> --
<>> Posted using the http://www.windowsforumz.com interface, at author's
<>> request
<>> Articles individually checked for conformance to usenet standards
<>> Topic URL:
<>>
http://www.windowsforumz.com/General-Discussion-Turning-Hyperthreading-XP-ft
opict431889.html
<>> Visit Topic URL to contact author (reg. req'd). Report abuse:
<>> http://www.windowsforumz.com/eform.php?p=1450217
<>>
<
<
<
Click to expand...
 
R. McCarty said:
Thanks - I'll add the KB to my references links
Click to expand...

You're welcome. It suprised me. I assumed I'd have to do a repair install.
When the repair install wasn't needed I did some searching to find out why.

Kerry
 
Hello,
You are correct changing the hyperthreadingsupport in the bios shouldn't
change the APIC. I am not aware of any bui setting that would affect APIC,
however I cannot state definatively that there are no settings in the bios
that affect whether a machine reports itself as APIC or not.
So I was trying to leave open the possiblity that such a setting exists. I
probably wasn't clear enough in posting
Thanks,
Darrell Gorter[MSFT]

This posting is provided "AS IS" with no warranties, and confers no rights
--------------------
<From: "R. McCarty" <[email protected]>
<References: <[email protected]>
<[email protected]>
<[email protected]>
<[email protected]>
<[email protected]>
<Subject: Re: Turning Hyperthreading on/off with XP
<Date: Wed, 12 Oct 2005 21:32:43 -0400
<Lines: 96
<X-Priority: 3
<X-MSMail-Priority: Normal
<X-Newsreader: Microsoft Outlook Express 6.00.2900.2670
<X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670
<X-RFC2646: Format=Flowed; Original
<Message-ID: <[email protected]>
<Newsgroups: microsoft.public.windowsxp.general
<NNTP-Posting-Host: user-1120rc9.dsl.mindspring.com 66.32.109.137
<Path: TK2MSFTNGXA01.phx.gbl!TK2MSFTNGP08.phx.gbl!TK2MSFTNGP15.phx.gbl
<Xref: TK2MSFTNGXA01.phx.gbl microsoft.public.windowsxp.general:478910
<X-Tomcat-NG: microsoft.public.windowsxp.general
<
<I follow most of your explanation, except on the APIC ( Advanced Peripheral
<Interface Controller. Changing the Hyperthreading support in BIOS wouldn't
<affect that in any way - would it ? Doesn't an APIC simply extend the
normal
<IRQ range up to 23 ? No big issue, but on my Intel 865 ( ACPI Mult...HAL)
<if I turn off Hyperthreading in BIOS the HAL stays the same on a boot back
<into XP, doesn't change from Multi->Uni
<Thanks for the info -
<
<<> hello,
<> That's not actually correct.
<> When you install the machine, setup tries to make a detemination whether
<> the machine is PIC or APIC.
<> If the motherboard is multi-processor aware, it should install the APIC
<> hal, even with a single processor.
<> Enabling hyperthreading in the bios after the fact and rebooting should
<> autodetect the second processor and make any changes.
<> Enabling or disabling hyperthreading should not change the fact that the
<> motherboard is APIC.
<> As long as APIC is detected it should work properly.
<> Unless there is an option in the bios to change from PIC to APIC or from
<> APIC to PIC, enabling hyperthreading or disabling hyperthreading in the
<> bios should not prevent the OS from recognizing the changes.
<> However if HAL is forced during setup using the F5 key, then the
<> auto-update is disabled for future changes.
<> If setup does not correctly detect the motherboard as APIC, it will not
<> reflect the changes either.
<> Thanks,
<> Darrell Gorter[MSFT]
<>
<> This posting is provided "AS IS" with no warranties, and confers no
rights
<> --------------------
<> <From: "R. McCarty" <[email protected]>
<> <References: <[email protected]>
<> <[email protected]>
<> <[email protected]>
<> <Subject: Re: Turning Hyperthreading on/off with XP
<> <Date: Wed, 12 Oct 2005 20:07:10 -0400
<> <Lines: 37
<> <X-Priority: 3
<> <X-MSMail-Priority: Normal
<> <X-Newsreader: Microsoft Outlook Express 6.00.2900.2670
<> <X-RFC2646: Format=Flowed; Original
<> <X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2670
<> <Message-ID: <[email protected]>
<> <Newsgroups: microsoft.public.windowsxp.general
<> <NNTP-Posting-Host: user-1120rc9.dsl.mindspring.com 66.32.109.137
<> <Path: TK2MSFTNGXA01.phx.gbl!TK2MSFTNGP08.phx.gbl!TK2MSFTNGP15.phx.gbl
<> <Xref: TK2MSFTNGXA01.phx.gbl microsoft.public.windowsxp.general:478862
<> <X-Tomcat-NG: microsoft.public.windowsxp.general
<> <
<> <You can turn off Hyperthreading in the BIOS and the Multiprocessor
<> <HAL will continue to work. However, if you installed with a "Single"
<> <CPU HAL like ACPI (without Multiprocessor) and then turn on the
<> <Hyperthreading in BIOS, XP will continue to see/use only a single CPU.
<> <So it works one way and not the other.
<> <
<> <<> <> O.K. :) That's 2 replies - one says I can do it, the other says I
<> can't.
<> <> :) Now what?
<> <>
<> <> "Sparda" wrote:
<> <>
<> <>> "" wrote:
<> <>> > Can I reboot XP, turn hyperthreading on/off in the BIOS, boot
<> <>> > back into XP
<> <>> > and XP with see that hyperthreading is either on/off and run
<> <>> > accordingly? Or
<> <>> > are there other settings or things to take into consideration?
<> <>>
<> <>> You probably don;t want to do this, as windows XP (unpon instalation)
<> <>> will have configured itâ?Ts self for two CPUs (Since when hyper
<> <>> threading is enabled it treats them as two CPUs). So turning it off
<> <>> with out reinstalling windows will probably result in system
<> <>> instability in the best situation.
<> <>>
<> <>> --
<> <>> Posted using the http://www.windowsforumz.com interface, at author's
<> <>> request
<> <>> Articles individually checked for conformance to usenet standards
<> <>> Topic URL:
<> <>>
<>
http://www.windowsforumz.com/General-Discussion-Turning-Hyperthreading-XP-ft
<> opict431889.html
<> <>> Visit Topic URL to contact author (reg. req'd). Report abuse:
<> <>> http://www.windowsforumz.com/eform.php?p=1450217
<> <>>
<> <
<> <
<> <
<>
<
<
<
 
You can turn HT off during the XP boot. Goto Control
Panel/System/Advanced/Startup
and edit the boot.ini file. Copy your existing line and append "/numproc=1"
and insert "HT
Off" between the OS description the end quotation marks. When you boot you
can then
choose between normal operation or HT off.

Example:
multi(0)disk(0)rdisk(0)partition(1)\WINXP="Microsoft Windows XP Pro HT Off"
/noexecute=optin /fastdetect /numproc=1
 
hi, i need to turn off hyper-threading, im using Windows XP Home (fujitsu
siemans laptop) what words shall i type in the boot file when i edit it? im
not sure. pkease help!
kindest Regards
Dean
 

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