Hi..
 > CH> The Cx486 SLC/DLC/s/s2/sx/dx/dx2/dx4/5x86 don't support
 > CH> CPUID. The 6x86 has CPUID turned off by default.
 > CH> The 6x86MX & MediaGX have CPUID turned on by default.
 > You sure the 5x86 doesn't support CPUID?
Absolutely. I have at least 5 of them here to test any time. Yes, I have 
tried CPUID and all sorts of combinations of cyrix config registers literally 
hundreds
of times on these chips with no success.
Also, I have the Cyrix 5x86 CPU manual in paper and electronic forms - no
mention of CPUID anywhere.
 > I haven't had an opportunity to check the 6x86MX and MediaGX yet, but if
 > it is on by default, then GOOD; they finally turned their brains on...
Exactly. And about time too.
 > CH> Furthermore, attempting to enable CPUID in a 6x86 requires
 > CH> writing to ports 22h and 23h - which many older motherboard
 > CH> chipsets use as their setup/config ports; writing to them
 > CH> usually crashes the computer! (ie most/many 286, 386 and
 > CH> early 486 chipsets, including G2, C&T NEAT, & anything with
 > CH> an 82c206).
 > One can get around this partially by both checking the flags to see if
 > they're handled in a Cyrix manner, and then checking that the CPU is a
 > Pentium-class or better.
The 6x86 does not use the flags in the same manner as earlier Cyrix CPU's. 
Most coders use CPUID to 'check that the CPU id pentium class' - catch 22 
situation. Granted, one could test for a common pentium+ opcode such as rdmsr 
or something and work on that basis.
 > Do you know if ports 22h and 23h are always used the same way in all of
 > the chipsets, i.e., write index to 22h and read value from 23h?
Chipset behaviour varies enormously. Many are documented in Ralf Brown's 
interrupt list. No, 22h and 23h aren't always used as address:data pairs. 
Sometimes 24h is used as the data port, and 26h,27h and 28h are other popular 
ports.
Take it on my experience: there is no uttely safe way to reliably detect the 
cyrix 6x86 without accesing ports 22h and 23h.
    Craig
--- FMail/386 1.20+
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