RE: [X86] Fix up silly i1586 boot message.

Yuhong Bao
2009-10-28T03:14:17Z

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> Intel started it first with picking up a ridiculous number for the family
> ID for the P4 line. There is no technical justification for not keeping
> these numbers consecutive.=20
Well=2C the problem was that Intel has assigned family 7 for the original I=
tanium processor=2C back when Intel thought that would replace x86 (the cod=
ename for the original Itanium was P7=2C and the codename for the original =
P4 was P68). And then there was a bug in original NT 4 truncating family ID=
s returned by CPUID to 3 bits. This was not the only bug in the original NT=
4's CPUID code=2C there was another bug relating to CX8 detection with non=
-Intel/AMD/Cyrix processors forcing the other CPU vendors to provide an opt=
ion to mask this bit=2C which caused trouble for MS itself later on when th=
ey decide they would begin to require CX8 in XP=2C and it ignores CPUID if =
max standard CPUID level is greater than 3=2C forcing Intel to again add a =
workaround into their Prescott and later processors.
Geoff Chappell wrote articles describing these problems in NT 4:
http://geoffchappell.com/viewer.htm?doc=3Dstudies/windows/km/cpu/index.htm
http://geoffchappell.com/viewer.htm?doc=3Dstudies/windows/km/cpu/cx8.htm

Yuhong Bao
=20
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