[RC5] Tillamook cpu selection problem

Trevor Hemsley Trevor-Hemsley at dial.pipex.com
Sun Nov 30 00:24:04 EST 1997


On Sat, 29 Nov 1997 18:25:15 -0500, Jim McManus wrote:

>I ran the benchmark from the GUI and, no surprise,  the pentium, pentium MMX
>core was the fastest. I was curious how the processor is determined. I noticed
>that when NT starts is somehow knows it's in a "genuineintel" processor. Does
>the code look for something embedded in the processor that is returned when
>some certain instructions are run? 

NT uses the CPUID instruction which returns the manufacturer name in
register EBX, ECX and  EDX as well as a bunch more information. The
possible returns are "GenuineIntel" (Intel) "AuthenticAMD" (AMD)
"CyrixInstead" (Cyrix)  "NexGenDriven" (NexGen) "CentaurHauls" (IDT)
and "UMC UMC UMC " (UMC).

Based on the processor family, model number and stepping number it's
possible to determine with a fair degree of accuracy what the processor
is. The CPUID instruction is only available on more recent processors -
some 486's don't have it and nothing prior to the 486.

I don't think the RC5 client uses this - though it could.


Trevor Hemsley, London, UK.
Trevor-Hemsley at dial.pipex.com or 75704.2477 at compuserve.com


Trevor Hemsley, London, UK.
Trevor-Hemsley at dial.pipex.com or 75704.2477 at compuserve.com

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