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Index > Windows > Completely disable one of cores

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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
hi, doesn't someone happen to know some way to completely disable one of cores in windows? I need to disable it for kernel thread too. Thanks.
Post 04 Jul 2007, 18:14
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Filter



Joined: 08 Oct 2006
Posts: 67
Filter
You mean for a multi-core processor? It would be a BIOS option. If you want to do it from an application I wouldn't know how.
Post 04 Jul 2007, 19:32
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
I believe Windows does have such option.

anyway, thanks for idea, for now i will do it in BIOS
Post 04 Jul 2007, 19:38
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cubeoid



Joined: 22 Jan 2007
Posts: 19
cubeoid
You can disable 1 core by setting all processes to 1 core
Its called setting a processes Affinity

I know its not exactly the same but its the only way i can think of doing it
Post 10 Jul 2007, 16:53
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
f0dder
Out of interest, why do you need to disable a core?
Post 11 Jul 2007, 11:26
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Garthower



Joined: 21 Apr 2006
Posts: 158
Location: Ukraine
Garthower
Filter wrote:
You mean for a multi-core processor? It would be a BIOS option. If you want to do it from an application I wouldn't know how.


I don't have such option in my BIOS... You can have in view of a diasble/enable a Hyper-Threading?
Post 11 Jul 2007, 14:16
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
f0dder: i am playing with VMX stuff, and since VMX only support virtual machines with single core, windows shouldn't expect it runs in multi-core evironment.
Post 11 Jul 2007, 15:11
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
f0dder
Oh... I dunno if there's some CRx bits you can play with for that, but I suspect it's some ACPI/whatever tables you should modify before you launch windows in the VMX? Haven't seen a BIOS that supports turning off cores, only HT.
Post 11 Jul 2007, 23:30
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
I do have that option in my BIOS, or at least i think. It is called "Core Multi-Processing".

But problem is i will need to disable it while windows is running, so i think just disabling it in CPU registers will "confuse" windows
Post 12 Jul 2007, 10:56
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Filter



Joined: 08 Oct 2006
Posts: 67
Filter
Garthower wrote:
Filter wrote:
You mean for a multi-core processor? It would be a BIOS option. If you want to do it from an application I wouldn't know how.


I don't have such option in my BIOS... You can have in view of a diasble/enable a Hyper-Threading?


Hyper-Threading is not multi-core. It just gives the OS the feeling of having two CPUs for the purpose of increasing the register count and in theory increasing the processors processing power.

Vid, I'm still confused why you would need to disable one core even if VMX doesn't support both cores. Can you explain further please? There are many things I don't know and this I would like to learn.
Post 13 Jul 2007, 12:37
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HyperVista



Joined: 18 Apr 2005
Posts: 691
Location: Virginia, USA
HyperVista
Filter - while VMX does not preclude the use of multi-cores, it is quite difficult to manage VMs in a multi-core system. When trying to get a VMX system up and running, it's best to make your work as easy as possible. Restricting the platform to one core is a grand simplification when you're first designing, writing and debugging your beta VMX based VM. It's learning to walk before you run Laughing

Check out this paper on a VMX based rootkit. The author discusses the difficulties with multi-processors with respect to VMX. He admits he disables one of the cores in order to get his demo working (see pages 25 and 36 of his paper).
Post 13 Jul 2007, 16:20
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