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SubjectRe: [Q] Cyrix/IBM 6x86 ?
Date
> 
> On Mon, 25 Mar 1996, Harald Milz wrote:
>
> > is anyone working on adaptations for the Cyrix/IBM 6x86?
>
> What's to port? The Cyrix Web pages indicate Linux compatibility -- is
> there some other [un]*known problem?

There are some optimizations which are not configured by all boards (The
Tyan S1468 comes with a 6x86-aware BIOS, and the Micronics M54Hi-02p at
least recognizes the CPU). OTOH, you can hardly use another board because of
the large amount of current the CPU draws from the power supply. Normal
"type 5" sockets aren't specified for more than 4.5 A, and the P120+ (100
MHz) pulls 4.8A at the DOS prompt. This gives you interesting problems with
standard power regulators...

But for instance, it has a power saving HLT instruction, and to activate
it, you have to set bit 3 in CCR2. If activated, the CPU needs only 30 mA
in HLT, otherwise 3.6 A and more. (sic!) Things like "Data forwarding",
"Fill on Write Miss", "Write Gathering", "Weak Ordering" etc. are powerful
options which aren't supported by Pentiums, and you have to enable them
manually (by accessing ports 22h/23h). That's what I ask for. Otherwise,
many performance optimizing options aren't used, and the CPU acts like
a normal Pentium. According to c't magazine, April 1996, pp. 196-202, the
6x86-P166+ (133 MHz) is slightly faster than a P166 if the said
optimizations are used.

If anyone is interested, there is a configuration file cx686.cfg for the
configuration tool ct-chipzx on ftp.ix.de:/ct ... (don't know the complete
pathname, archie might help).

> http://www.cyrix.com/support/sw-list.htm

I bet this is not written on the Web page. :-)

Ciao,
hm

--
Harald Milz (hm@seneca.muc.de)

Home of Doberman Propulsion Laboratories:
The ultimate in watchdog weaponry.
-- Chris Shaw


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