2GB address space limit on 32-bit PowerPC Macintosh

Wolfgang Denk wd at denx.de
Tue May 17 02:11:03 EST 2005

In message <1116255938.5095.133.camel at gaston> you wrote:
> I suppose it would add about ... 1 instruction :) Which is probably
> barely measurable compared to the cost of the cache misses of getting to
> the page table entires...

That would be just another "just 1 instruction"  modifircation  to  a
time  critical path in a kernel which already now is so slow compared
against an old 2.4 kernel that I'm really surprised to  nobody  seems
to care.

> But I agree that we don't abolutely _need_ to break everybody. Maybe a
> better compromise would be to have the default beeing per CPU family ?
> 6xx/7xx/7xxx could default to 3G and 8xx stay at 2G...

How many systems actually need this? Why make the <1% of the  systems
that need it the default?

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Q: Why do PCs have a reset button on the front?
A: Because they are expected to run Microsoft operating systems.

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