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JWong19
Beginner
129 Views

Highest valid sub-leaf index of CPUID(EAX = 0DH)

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I refer to the document of ISA extensions at <https://software.intel.com/sites/default/files/managed/07/b7/319433-023.pdf>. (page 2-18)
 
 
The highest valid sub-leaf index, n, is
(POPCNT(CPUID.(EAX=0D, ECX=0):EAX) + POPCNT(CPUID.(EAX=0D, ECX=0):EDX) - 1)
 
 
How to obtain this formula of the highest valid sub-leaf index of CPUID.0DH?
I expect that it should be the most-significant bit of CPUID.(EAX=0D,ECX=0).[EAX:EDX] instead, because the sub-leaf index corresponds to bit position of CPUID.(EAX=0D,ECX=0).[EAX:EDX]
 
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MarkC_Intel
Moderator
129 Views

Doc bug. 

I will ask the doc team to try sync the CPUID stuff up again. 

See the latest SDM instead: http://www.intel.com/sdm

 

 

 

 

 

 

View solution in original post

2 Replies
MarkC_Intel
Moderator
130 Views

Doc bug. 

I will ask the doc team to try sync the CPUID stuff up again. 

See the latest SDM instead: http://www.intel.com/sdm

 

 

 

 

 

 

View solution in original post

JWong19
Beginner
129 Views

Thanks for confirmation of the bug

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