"Max CPUID Value Limit" What is it?

[flibberdipper]

In the BIOS of my sister's netbook, there's an option under the CPU settings to enable or disable an option called "Max CPUID Value Limit." In the sidebar where it gives you info about it it says "Disabled for WindowsXP." Right now I have it at Disabled, just to be safe-ish. I plan on either putting Windows 7 Home Premium 32-bit or Puppy Linux 5.7.1 on it, so should I enable it or disable it? And what the hell does it even do?

[Si3Rra_7]

Interested too in the answer . 

[Speedbird]

No idea, but keep it disabled. I've heard that it's for older OSs....

[flibberdipper]

No idea, but keep it disabled. I've heard that it's for older OSs....

Turning it off is, apparently.

[Speedbird]

Turning it off is, apparently.

No, I meant for DOS-based Windows, like 95 and 98.

[flibberdipper]

No, I meant for DOS-based Windows, like 95 and 98.

Oh. I'll wait for more people to say what it is though (not that I don't trust you, I'm just that kind of person).

[Archangel1994]

Well I found this page

http://www.techarp.com/showfreebog.aspx?lang=0&bogno=362

 

Edit:

 

Max CPUID Value Limit: This is mainly used for Intel Pentium 4 processors with HyperThreading technology. It allows higher level CPU ID values to be used like 03h (hexadecimal values). This only needs to be enabled if the operating system does not support specific features. Note: For all later versions of windows this does not need to be activated, same with most Linux distributions. Just so you know what it does, CPUID as the name suggests gets information about the processor, the higher the value it supports the more information is able to be obtained.

 

From: http://www.overclock.net/t/55367/does-anyone-know-what-these-bios-options-mean

[Volbet]

It's pretty hard to explain, but here is my try.

When your system boots up, the OS is requesting the CPU to indentify itself. This is done via the CPUID instructions.

The problem occurs when Hyper Threading enter the picture.

Some older operating systems aren't capable of recognizing hyper threaded cores, since the CPUID value is to high. This can cause issues.

The ´Max CPUID Value Limit´, limites the CPUID ot the lowest that older operating systems can recognize, hence circumventing the problem. 

Essentially, if you are running a OS that is XP or newer, you don't need to turn it on, since these are capable of recognizing hyper threaded core.

[flibberdipper]

It's pretty hard to explain, but here is my try.

When your system boots up, the OS is requesting the CPU to indentify itself. This is done via the CPUID instructions.

The problem occurs when Hyper Threading enter the picture.

Some older operating systems aren't capable of recognizing hyper threaded cores, since the CPUID value is to high. This can cause issues.

The ´Max CPUID Value Limit´, limites the CPUID ot the lowest that older operating systems can recognize, hence circumventing the problem. 

Essentially, if you are running a OS that is XP or newer, you don't need to turn it on, since these are capable of recognizing hyper threaded core.

So you would enable it if you were running something like W2K?

 

Well I found this page

http://www.techarp.com/showfreebog.aspx?lang=0&bogno=362

 

Edit:

 

Max CPUID Value Limit: This is mainly used for Intel Pentium 4 processors with HyperThreading technology. It allows higher level CPU ID values to be used like 03h (hexadecimal values). This only needs to be enabled if the operating system does not support specific features. Note: For all later versions of windows this does not need to be activated, same with most Linux distributions. Just so you know what it does, CPUID as the name suggests gets information about the processor, the higher the value it supports the more information is able to be obtained.

 

From: http://www.overclock.net/t/55367/does-anyone-know-what-these-bios-options-mean

That confused the hell outta me.

[Archangel1994]

So you would enable it if you were running something like W2K?

 

That confused the hell outta me.

In short, the higher the CPUID value the more info can be obtained about the processor by the CPU. This is really only an issue for the Pentium 4 CPU's. You need this on older OS's due to lack of function/feature support

[Volbet]

So you would enable it if you were running something like W2K?

 

That confused the hell outta me.

You would, yeah. Although it has been nearly 12 years since I last worked with Windows 2000, so I can't be completly certain.

I should probably mention, that Linux don't really have this issue, especially versions that aren't 13+ years old.

[Sharif]

Since its solved i can speak about

/offtopic 

I was following this thread as i was curious as well