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SubjectRe: [Q] Cyrix/IBM 6x86 ?


On Wed, 27 Mar 1996, Alan Cox wrote:
> > 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
>
> Weak ordering if its doing write re-ordering will need to go on/off as you
> access stuff like WD80x3 ethernet cards. The other stuff ought to be ok on
> the whole. Try it and see - you can access 22h/23h from a root program with
> ioperm().

I'd assume that the 6x86 has a few "range" registers to mark _which_
areas of memory can be weakly ordered. That's how the PPro does it, and
it's the only sane way to go (alternatively you can do it on a page-table
basis, that's fine too and has some other advantages).

Anyway, the way to do all this is to make a loadable module that sets up
the registers and then exists (the IO ports you can do from user space,
but any control registers probably need the module approach anyway)

Linus


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