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Topic Title: How to tell if CR4 is implemented?
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Created On: 03/27/2004 04:16 PM
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 03/27/2004 04:16 PM
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sudleyplace
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Joined: 03/27/2004

How can I tell (under program control) if an AMD processor implements CR4?

On Intel CPUs, if the processor supports the CPUID instruction, then it supports CR4. Apparently this is not the case on AMD CPUs as the Am5x86 processor shows.

At the moment, the best I can come up with is

If AMD processor and Family level is 5 or greater,
then the processor supports CR4.
 03/27/2004 06:09 PM
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Greyhound
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Joined: 10/07/2003

hmmm...i have no idea what 'CR4' is, but you can find the Datasheet for the Am5x86 here' ">http://www.amd.com/us-en/asset...nd_tech_docs/19751.pdf...and here's' ">http://www.amd.com/us-en/asset...nd_tech_docs/20734.pdf AMD's Processor Recognition Application Note which deals with the CPUID-instruction on AMD processors.

Hope this helps

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 03/27/2004 07:12 PM
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sudleyplace
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Thanks for your reply. CR4 is Control register #4. I appreciate that it is not referenced in the K5 docs, and is referenced in the K6 docs. so one is tempted to come to the conclusion I came to in my initial message. Rather than jumping to such a conclusion (as I do not have detailed knowledge of AMD CPUs), I was hoping that someone who knew the line inside and out would be able to say exactly what the story is.
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