[Cialug] Opteron and 64 bit architecture question

[Nathan C. Smith]

Needless to say you are happy with Opteron?

What do you do with all those machines?  ;-)

-Nate

-----Original Message-----
From: Aaron Porter [mailto:atporter@gmail.com] 
Sent: Tuesday, April 26, 2005 4:22 PM
To: cialug@cialug.org
Subject: Re: [Cialug] Opteron and 64 bit architecture question



On 4/26/05, Nathan C. Smith <smith@ipmvs.com> wrote:
> My question is, if you run a 32 bit program on a 64 bit machine 
> (particularly AMD), does it have to recreate this memory access kludge 
> in the "emulation mode", or is this one of the ways it can give a 
> little boost to a 32 bit system running on a 64 bit architecture.

The "kludge" was for the OS to access more than 4gb, your applications were
generally still limited to under 4.

> If I buy 64 bit machines now, and run 32 bit Oss on them, I will be 
> future-proofed to some degree, but will I get any benefit for the 32 
> bit OS today?

Yes, but mainly from the memory hardware. AMD's HyperTransport kicks the
pants off Intel's stuff.

> Anyone with an Opteron happy with it in 64 or 32 bit "mode"?  I have 
> an Athlon 64 Machine at work running Fedora Core 3 64.  It is a fast 
> machine, but I can't say that is is significantly faster than other 
> machines, subjectively, it actually "felt" faster running 32 bit FC3.

I've got ~150 dual cpu opterons running Debian Sarge i386 with a home-brew
amd64 kernel. The vast majority of our apps are 32bit binaries, and the
developers are months away from starting the
(trivial) process of recompiling. We've seen anything from a 30-80% speed
increase in run time (Opteron 246 @ 2ghz vs Xeon @ 2.2ghz) on the same
binarires simply because of the faster memory bus. Night and day for most of
our stuff.

We've also got Debian Sid amd64 running on a few of our larger boxes and
desktops, and it's  been rock solid. Nothing more satisfying than watching a
$10k amd64/debian box spank a $50k sun box.
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