Re: Pure 64 bootloaders

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On Sep 14, 2005, at 09:20:45, Lennart Sorensen wrote:
On Tue, Sep 13, 2005 at 11:44:55PM -0400, Kyle Moffett wrote:

PowerPC was designed 64-bit from the start too!  It's just that the
architecture design group also realized that there would be a demand
for 32-bit CPUs, and so from the _64-bit_ system, they designed a 32-
bit system whose entire instruction set would be forward-compatible
to 64-bit systems when they came out.  That's why 32-bit PowerPC
machine code and 64-bit PowerPC machine code are completely identical
except that 64-bit CPUs also have a few opcodes to process 64-bit
data and a few extra kernel-mode registers.

Hmm, so how does that fit with needing both 32 and 64bit libraries on a ppc system? It seems apple forgot the 64bit part of a library recently
in a security fix, or is that something more to do with their os than
the cpu?

Well, if you want to pass 64-bit pointer values to a library, the library needs to have functions that take 64-bit values and use 64- bit operations on them, just like all the other archs :-D. It also needs 32-bit compatibility functions for the old 32-bit-only programs. On the other hand, if you don't care about compatibility with 32-bit-pointer programs, you can omit functions that deal with 32-bit pointers and require everything to use 64-bit pointers. You still need stuff like atoi that uses 32-bit values, though, and 64-bit-only does have a performance penalty.

Cheers,
Kyle Moffett

--
There is no way to make Linux robust with unreliable memory subsystems, sorry. It would be like trying to make a human more robust with an unreliable O2 supply. Memory just has to work.
  -- Andi Kleen


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