Subject: Re: CCL:Summary Opteron vs Nocona

From: Mikael Johansson <mpjohans :: pcu.helsinki.fi>
Date: Tue, 17 May 2005 10:58:33 +0300 (EEST)

Hello Luigi and All!

On Tue, 17 May 2005, Luigi Cavallo wrote:

> However, there's one point about opterons. AMD just announced dual-core cpus,
> which should perform far better than the single-core shipped now.
> I contacted resellers here in italy, and they say that dual-core cpus will be
> shipped after the summer. If you buy opetrons now they can sell you single-core.
> Is this true ? Any out of there has been able to buy AMD with dual-core cpus as
> the 275 ?

I don't know about AMD's mass shipping schedule, but I do know that there 
will always be better and faster chips "after the summer". Or winter or 
whatever time period of choice :-) I don't think it in general is worth 
waiting for the next family of CPU's. Instead, get what is available when 
you need it (if possible, of course). I don't know how much better the
price/performance ratio of dual cores would be, at least in the beginning, 
when counting in all the costs of motherboards etc.

Also, after the dual core chips ship, there will be a lag before proper 
drivers/kernel patches for Linux appear. It took a year after release 
before a general AMD64 system could be considered usable for production 
under Linux. OK, the jump to dual core might not be that big, but I would 
be quite surprised if it immediately worked optimally.

Have a nice day,
     Mikael J.
     http://www.helsinki.fi/~mpjohans/

---

From: Mark Hahn <hahn^at^physics.mcmaster.ca>
Date: Tue, 17 May 2005 13:11:40 -0400 (EDT)

> > which should perform far better than the single-core shipped now.

for cache-friendly applications that don't mind somewhat lower clocks.

> waiting for the next family of CPU's. Instead, get what is available when 

it depends on how advantageous the change is.  for instance, if you are 
heat or footprint-constrained in your machineroom, AMD's dual-core might 
well be worth waiting for, since they are compact and noticably cooler 
than two single-core chips.

> when counting in all the costs of motherboards etc.

if you have cache-friendly code, dual-core is very effective.
other components are basically the same, therefore no price premium.

AFAIKT, AMD hasn't announced DC pricing yet:
http://www.amd.com/us-en/Weblets/0,,7832_8366_609,00.html
the premium for 8xx chips is noticably higher than twice the 
price of the same-clock single-core.  but of course you save 
with fewer motherboards, chassis, etc.

> drivers/kernel patches for Linux appear. It took a year after release 

no, DC is such a minor architectural change that it's already supported.

regards, mark hahn.
sharcnet/mcmaster

---

From: Rich McClellan <richmc)at(gmail.com>
Date: Tue, 17 May 2005 11:36:00 -0700

Hi Mikael,

The dual core Opterons are pin compatible with current Opterons and only a 
BIOS update should be necessary. Given that most OSes in use support 
multiple processors, no new drivers, kernel patches, etc., are required. 
That is, flash your BIOS, install a dual core CPU, boot your OS (with kernel 
that supports SMP), and you're done. Because the single and dual core 
processors are pin compatible, Luigi could order/build his cluster today and 
swap CPUs for dual core Opterons in 6-12 mos.

Rich

On 5/17/05, Mikael Johansson <mpjohans)at(pcu.helsinki.fi> wrote:
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