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SubjectRe: [PATCH] Cyrix setup
On Mon, 9 Mar 1998, Ragnar Hojland Espinosa wrote:

> Mike Jagdis <mike@roan.co.uk> wrote:
>
> > Not setting the Cyrix to go low power on hlt breaks the existing
> > assumptions in a way that is just plain *dumb*!
>
> No, not setting the hlt on isn't dumb. I have a M2, and before buying it
> I recall seeing reports from people who had problems with hlt. IMHO, people
> are right in saying that it would be a bad thing to move set6x86 into the
> kernel since there's no real need or benefit for it.

Can we just get one thing *clear*? Linux uses the hlt instruction
in the idle loop *unless* the boot option "nohlt" is used. The
reason hlt is called is because, on Intel chips, hlt drops the
CPU into a low power mode. The reason the "nohlt" boot option
is there is because some motherboards have problems with a CPU
in low power mode (wake up, DMA interference, weird stuff that
shouldn't happen).

Now the default power up mode of the 6x86 is to *not* go low
power on hlt thus avoiding problems with broken systems. This
also renders the use of hlt pointless. And we *already* have a
workaround for broken systems in the form of the "nohlt" boot
option.

So: leave the 6x86 in halt-and-heat mode and explain to end users
that they need to know what CPU is in the box, where to find set6x86,
how to use it, what the "magic" CPU I/O ports are, how to change
them etc. *OR* set the 6x86 to suspend-on-halt and allow the existing
kernel support and workarounds to function *AS THEY ARE DESIGNED
AND DOCUMENTED TO*.

N.B. Yes, if you leave the CPU in halt-and-heat mode you *MUST*
explain to end users how to set up and use set6x86. The 6x86 runs
pretty damn hot under load anyway. It takes a heft CPU fan. CPU
fans tend to wear all too fast and often stop with no visible
indication until your CPU suffers heat damage and your system
becomes "unstable". Using suspend-on-halt reduces running temperature
and power consumption *significantly*.

Mike

--
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| Mike Jagdis | Internet: mailto:mike@roan.co.uk |
| Roan Technology Ltd. | |
| 54A Peach Street, Wokingham | Telephone: +44 118 989 0403 |
| RG40 1XG, ENGLAND | Fax: +44 118 989 1195 |
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