Re: Apple, Jobs, and the irony of it

[Eric Smith <eric-no-spam-for-me@brouhaha.com>]

"Charlie" <charlied@NOSPAMbboard.com> writes:
> How does the Opteron run 32-bit applications?  The AMD website and the
> Opteron data sheet are vague about how it is done.

In a compatability mode.  However, since the AMD64 architecture is mostly
a superset of the x86-32 architecture (with a few minor changes to instruction
encoding), allmost all of the fancy hardware they designed into the Opteron
actually is used to get great performance in 32-bit mode.

> 32-bit applications on an Itanium 2 run in "compatibility mode" which
> is a mode that is NATIVE to the processor.

It's native to the processor, but it's implemented as a bag on the side,
because the native IA64 architecture is *completely* different than the
x86-32.  Itanium 2 performance for x86-32 code is *terrible*.

> Certainly, the Opteron was meant to be a transition chip (to make the
> transition from 32-bit to 64-bit easier) and from what I've read they have
> succeeded, but in my opinion it is not the first 64-bit processor to run a
> mainstream operating system.

Quite true, that was the Alpha running Windows NT.