Re: context overflow

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 [off-list ref]
MontaVista Software, Inc

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