[RC5] Cyrix M2-300

Mike Silbersack silby at execpc.com
Thu Jul 16 10:55:02 EDT 1998

On Wed, 15 Jul 1998 19:56:50 GMT, Khouri Giordano wrote:

>I set up a few Cyrix M2-300 (233MHz) machines to process RC5 and they
>do 550 kkeys/sec. My main machine is a K6-233 which does 380
>kkeys/sec. Now that we've switch to DES, the Cyrix's do 800 and the K6
>does 1400. The software detects the K6 properly and uses the MMX core,
>but it detects the M2's as "Cyrix 486". I had to force the software to
>use the 6x86 core but it doesn't use the MMX core.
>Will the MMX core be put into the DOS client soon? I have 3 out of 4
>of the Cyrix machines running DOS.
>Khouri Giordano

The 6x86 series chips being detected as 486es is a flaw due to the fact
that cyrix made CPUID an instruction that must be turned on by the bios
(or other utility) each time at bootup (all other processor makers
decided that CPUID would never be disabled).  Evidently, many
bios/motherboard makers did not do this, and as a result, many 6x86es
around the world are detected as 486es.  I'm not going to redo the
client's cpu detect routines with cyrix specific code to work around
this (it would be as long as the main detection routine used for
everything else), but I'll make an override to enable mmx in version
2.7100.417 so 6x86mx owners can take advantage of their mmx

I'm unsure how soon a DOS MMX client will be available due to problems
we're having with the MMX core on older compilers.

Mike "Silby" Silbersack
silby at execpc.com
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