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Re: kernel selection: powerpc, power4 or power3?

On Wed, Jun 30, 2004 at 06:40:19PM -0500, Benjamin Herrenschmidt wrote:
> On Wed, 2004-06-30 at 15:48, Albert Cahalan wrote:
> > On Wed, 2004-06-30 at 07:27, Colin Watson wrote:
> > 
> > > No, -power3 is for POWER3 processors, used in older IBM RS/6000 systems.
> > > Similarly, -power4 is for POWER4 processors, used in iSeries, pSeries,
> > > and G5 systems. You want -powerpc. They aren't compatible in the way
> > > that -386, -686, etc. are.
> > 
> > The POWER3 instructions missing from PowerPC can be emulated.
> > You can go the other way too. This should allow for a truly
> > generic kernel, optimized for whichever processor you prefer.
> Well, the MMU is different, it's a 64 bits chip, so it uses a special
> bridge mode to run a 32 bits kernel, we don't quite deal dynamically
> with the various types of MMUs in the low level code on ppc32.

And it's better that way, IMHO. Low level MMU code is especially
critical, it should not be cluttered with conditionals and/or
indirect calls.

The only clean slution might be boot-time linking of the right
functions in the right place.


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