Re: Pure 64 bootloaders

[Kyle Moffett <mrmacman_g4@mac.com>]

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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