>On Mon, 2 Feb 1998, Steffen Grunewald wrote:
>
>> Hi list,
>>
>> recently I got an offer for an IBM6x86MX233 based computer. Looks
>> pretty good (even a bit faster than iPII-233 due to the larger cache)...
>> Are there any arguments against buying such a beast ?
>> Is there a FAQ on Linux' CPU support ? Perhaps a comparison of
>> performance and throughput ?
>> Are there (besides the ones that appeared in this mailing list past
>> weekend) any blacklisted single-processor main boards ?
>
>Linux supports every i386 model and up. However, in Linux-2.0.xx, there is
>no special code to recognize the 6x86 processors. So, the 6x86 is reported
>as a 486, whereas the 6x86MX is reported as a Pentium or PentiumPro (the
>difference is, that the 6x86MX has CPUID enabled by default.) The report
>as 486 or 686 has no problems, as far as I know.
>
>The 6x86 (and 6x86MX) have some special configuration registers which
can
>be used to optimize performance such as the Wt_Alloc (Allocate Cache
lines
>on Write). If you want to use these, you need a kernel patch or a program
>to set up the config registers.
>
>There are several programs and patches floating around. You can find my
>kernel patch against 2.0.33 (a pretty fat one) on
>ftp://student.physik.uni-dortmund.de/pub/linux/kernel/patches/cyrix
>and some programs on
>ftp://student.physik.uni-dortmund.de/pub/linux/kernel/6x86/
>(cpudev, set-6x86)
>I call the patch fat, because it does a lot of the setup during the kernel
>initialization. Most of it could be done in userspace (root) by programs.
>This alternative was followed by Andrew Balsa (and may be included into
>2.1.xx). He got a small kernel patch (mainly 6x86 recognition) and lets
>the program do the setup. Have a look at it's site:
>http://www.tux.org/~balsa/linux/cyrix
>You can find the set6x86-1.5 there. It includes the small kernel patch and
>the set6x86 program.
>
>If you got a system, where stability is important and you fear bad users,
>you have to apply one of the patches or use the set6x86 program to work
>around a processor bug, which is know as Hidden-CLI or Coma bug. Just
like
>the Pentium F00FC7C8 bug, it let's any (non-privileged!) user be able to
>crash the system. (The Pentium bugfix made it into the 2.0.32 kernel
>however.)
>
>--
>
>I got good experience with boards from FIC. I got a PA-2010+, which uses
>the VIA VPX chipset. It supports 75 and 83 MHz with async PCI bus, the
>6x86(MX) linear burst feature, up to 512MB cacheable area and EDO and
>SDRam. If you'd like to try 2.5x83.3MHz (208) instead of 3x66MHz (200),
>this would be the right joyce. (Or did you get a 2.5x75MHz (188) model?
>
>--
>
>I doubt, that the 6x86MX-233 is faster than a iPII-233. It is possibly
>faster than a iP233MMX as long as you don't start doing floating point
>calculations or using the MMX features, but the iPII-233 is superior.
Hardly. It is brute force faster, not technolically superior. A 6x86 P233 only
runs at 187MHz. A more impotant factor in over all system performance is
bus speed. I would take a 75x2.5 Cyrix over a 66x3 PII anyday. Drive
access, and memory I/O WILL be faster then the PII.
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