Re: [PATCH] Support new egcs/pgcc -mpentium(pro) options

Jamie Lokier (lkd@tantalophile.demon.co.uk)
Sun, 13 Dec 1998 17:15:44 +0000


On Sun, Dec 13, 1998 at 05:26:43AM +0100, Matthias Andree wrote:
> 3. What is the reason a 486 configured kernel will not run on the 386?
> It's evidently not the compiler as far as I can tell from my
> gcc-2.7.2.x/pgcc-1.1.1 documentation.

a. The kernel uses an instruction not present on the 386 (bswap?).

b. 386 memory protection is different from 486+ memory protection,
and the kernel has to work harder to support it securely. The
overhead for this is considerable. We prefer not to include that
code if we know it's not a 386.

On my to do list is a kernel option "compile for all x86 processors,
optimise for PPro (or whatever)". I'd be pleased to see someone else
do one first though :-)

-- Jamie

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