Re: New Cyrix patch for 2.0.33

Phil's Kernel Account (
Tue, 26 May 1998 15:22:04 -0400 (EDT)

On Tue, 26 May 1998, Rafael R. Reilova wrote:

#Hi Phil,

Hi Rafael! :)

#If more manufacturers start using ports 0x22 and 0x23, the we are really
#in for trouble, unless we are certain that we are dealing with a Cyrix.
#Cyrix assures that the port access won't generate external I/O for writes
#(if done correctly, of course), but first we need to know that it IS a
#Cyrix, which is a problem for CPUs with the cpuid off by default.

Right. And really, the ONLY place you're gonna see a Cyrix with cpuid off
is a Cx6x86. Everything else has cpuid on by default. The way I want to do
it is simple.

Is cpuid on?
if not test for BX @ 0x22, 0x23
if not there
turn on cpuid
if there
scream and yell about some stupid intel trick

now granted, that's REALLY simplified, but that's the basics of it.

#So it would be possible to have a BX-Cyrix(w/ cpuid) combo, but not a
#Cyrix w/o cpuid enabled and some random hardware at the same ports.
#Unless we test for every possible thing that may happen to lie at those
#addresses (currently only the BX chipset, but who knows what the hardware
#guys might come up with next).

I'd rather deal with the hardware idiots when they screw up like that, and
not before. ;)

#The assumptions made in Andre Balsa's patch are:
#1) basically that nothing without cpuid will ever be on a BX chipset (if
#this proves to be false, then I see you have a valid point).

It just may be. I'd rather take care of that small problem now, while
we've got a chance.

#2) any CPU that preserves flags across division and doesn't have cpuid, is
#probably a Cyrix and we may play with 0x22,0x23 ports (True w/ current

*VERY* close. Any CPU that does 0x22,0x23 and lacks cpuid on by default is
a Cx6x86. Any CPU that does 0x22,0x23 can be assumed to be a Cyrix. I
gotta be a nitpicker. ;)

-Phil R. Jaenke ( /
TheGuyInCharge(tm), Ketyra Designs - We get paid to break stuff :)
Linux pkrea.ketyra.INT 2.0.33 #15 Sat Apr 18 00:40:21 EDT 1998 i586
Linux 2.1.98 #15 Fri May 1 18:21:00 EDT 1998 i586
- Linus says for 'brave people only.' I say 'keep a backup.' - :)
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