Performa 5200

Benjamin Herrenschmidt bh40 at
Thu Aug 26 18:44:50 EST 1999

On Wed, Aug 25, 1999, Tony Mantler <eek at> wrote:

>I know the '040 maintains consistiency during the operation of alternate
>bus masters by snooping and spiking the bus according to what's in the
>cache. I haven't read up on how the PPC does it, but I would have expected
>it to be made code-level compatible with what the 040 does, atleast in
>these early PMacs.

I didn't check but someone (I think Paul) told me that snooping was not
done accross the PPC<->68k bus bridge used by those machines.

Note that I'm working on another cache-incoherent platform, and I'm
struggling with similar issues, I beleive we should manage to
"officialise" some vmalloc_uncached functions in the kernel for
cache-incoherent platforms (and define a standard way to tell a driver
it's running on a non-coherent machines). The current macros in io.h are
definitely not enough.
>Or something like that.
>Penguin collects a pile of LM globals and passes them in the bi struct, but
>most of those can be implied from the gestalt machine ID. Considering the
>number of NuBus PMacs, I don't think it would be terribly difficult to
>guess anything that's not passed in explicitly.

I think that's what MkLinux does.

>But, I shan't pay any note of it 'till *after* I get a kernel to boot. :)

Yep, of course ;-)

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