Multi-core processor and multiprocessor limit for Windows XP

Question

Processor architecture refers to either x86-32 (32-bit) or x86-64 (64-bit).

1.) What is the maximum quantity of cores in a physical processor of a PC that each edition and its corresponding processor architecture of Windows XP supports?

2.) What is the maximum quantity of physical processors of a PC that each edition and its corresponding processor architecture of Windows XP supports?

Answer 1

Hi Luigi A. Cruz,

The number of processors you can use depends on the version of Windows XP you use, though there are some caveats. Be sure to know what you're doing before you attempt to set up multiple processors.

Dual-Core

Microsoft's licensing policy limits the number of processors Windows supports for its Home and Professional versions, as outlined below. It's important to understand, however, that this is on a per-processor basis, not a per-core basis. This means that, under the licensing policy, a dual- or even quad-core processor counts as a single processor---something that confused many people in the early days of dual-core technology.

Versions of Windows

Knowing that, the limit of the number of processors is determined by your version of Windows XP. If you're not sure which version you're running, check the sticker on your computer. It will say the version there beside your license key; you may right-click "My Computer" and click "Properties." The window that pops up will tell you which version of XP you're running.

XP Home

The Home edition of Windows XP---the edition that came with most machines home users bought from the likes of Dell and HP, before Windows Vista---supports only one processor. This means if you want to install more than one processor and you run Windows XP Home, you may need to switch to Professional, or upgrade Windows to a newer version with support for multiple processors.

XP Professional

If you want to use two processors, Windows XP Professional is the way to go. While this advanced program cannot run more than two processors, this is an improvement over Home. Note that, because dual-core processors count as a single processor, you could theoretically have four cores with this license or even eight, if you are willing to buy two quad-core processors.

I suggest you to visit this below provided Microsoft KB article.

Processor and memory capabilities of Windows XP Professional x64 Edition and of the x64-based versions of Windows Server 2003

http://support.microsoft.com/kb/888732

Also refer:

XP Home supports 1 processor and XP Pro supports two processors, regardless of the number of cores.http://www.microsoft.com/licensing/about-licensing/multicore-processor-licensing.aspx#E1B

They can also check the max number of CPU’s on their own PC by going to Start > Run, typing  WINVER, and pressing the Enter key.  Then click on "End-User License Agreement".

http://social.microsoft.com/Forums/en-US/genuinebenefits/thread/1b6ea167-e9f1-4551-8793-0c86f1e6eed5

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Thanks and Regards:I. Suuresh Kumar - Microsoft Support. Visit our Microsoft Answers Feedback Forum and let us know what you think.

Answer 2

thanks for putting up the answer to this question it had been buggin g me all day, after having to re-install windows I found that task manager only had two cpu graphs showing wheras before it had 4.  Guess I need to get a copy of XP Pro instead :(

Answer 3

"This means that, under the licensing policy, a dual- or even quad-core processor counts as a single processor", so having a Windows XP pro, I should have no problem installing a QuadCore Q6600, right?

Problem is, while trying to install XP Pro, I get something like (after keying in the Product Key) "you product is only valid for 2 CPUs, not 4".

So apparently, 4 cores appear as 4 CPUs, thus I can't install Windows Pro.

So what can I do to install XP?

Answer 4

Hi,

Considering the age of the thread and to avoid confusion, if the troubleshooting steps in this thread did not resolve your issue I would recommend creating a new thread so that the community can focus on that thread. Refer to the following link prior to posting a question so that you may provide all the relevant information, for us to help you:

http://support.microsoft.com/kb/555375