Re: [Qemu-devel] Re: compile qemu for a G5

[André Braga]

On Tue, 12 Oct 2004 13:50:41 +0200, J. Mayer <address@hidden> wrote:
> Are you sure ?
> G5 is a 64 bits PPC, but POWER isn't: some instructions are not the same
> between the two architectures.  So, some Power4 opcodes and registers
> will never be recognized on any PPC. With luck, the Power code may run
> on PPC, but there's no waranty.

The PowerPC ISA is *broadly* compatible with POWER 's. I suggest you
to read up some technical documents on the subject. Plenty of them
have been made available at IBM's developer pages.

Moreover, POWER4 *IS* 64-bit, and -mcpu=power4 used to be the only way
to invoke G5-specific optimizations on GCC. I haven't kept myself
updated with the docs, though, and the flags were changed in some
later revision of the XCode (I don't have a G5-class machine, so I
thought it was somewhat pointless to know the details until I needed
them).


Here are the current recommended flags:
http://developer.apple.com/technotes/tn/tn2086.html#G5options

Here's some evidence on the -mcpu=power4 flag now-deprecated usage:
http://developer.apple.com/technotes/tn/tn2087.html#Section4
(scroll up a bit to the "Type conversion is costly" paragraph)


-- 
"A year spent in artificial intelligence is enough to make one believe in God"
Alan J. Perlis