Subject: Re: context overflow

From: Frank Rowand <[email-masked]>
Date: Wed, 07 Feb 2001 17:39:21 -0800

Paul Mackerras wrote:

> I think that it is seductive but misleading when the PPC docs say that
> the PPC supports a "large virtual address space".  Yes it does, in a
> sense, but it's not one that you can access directly on a 32-bit PPC;
> you have to go changing segment registers to get at all of it - i.e.,
> there's no such thing as a pointer into this space that the CPU
> understands natively.  You could have such a pointer as a 64-bit
> value, but to use it you have to split it apart and put one part in a
> segment register and make a pointer that the CPU understands out of
> the other part.  And the other thing is that there just aren't enough
> segment registers on 32-bit PPCs to be really useful (except as a way
> of coarsely partitioning the address space).

Then there are the PPC processors that don't even have segment registers....

> Paul.

-Frank
--
Frank Rowand <[email-masked]>
MontaVista Software, Inc

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