AMD64 models power consumption (Was: Athlon64 board with ECC support?)

[David O'Brien]

On Thu, Jun 23, 2005 at 06:37:41PM -0400, Martin Cracauer wrote:
> "David O'Brien" wrote on Mon, Jun 13, 2005 at 12:20:09PM -0700: 
> > On Mon, Jun 13, 2005 at 06:16:13PM +0200, Oliver Fromme wrote:
> > > I'm currently evaluating possibilities to upgrade to a
> > > 64bit system (preferably AMD).  I would like to get a
> > > single-processor Athlon64 system, no Opteron, because of
> > > heat, noise and power consumption (and price).
> > 
> > There is no difference between Athlon64 and Opteron with respect to heat,
> > noise and power consumption.  There is yes a price difference.
> 
> That is not strictly true for the idle case.  The Opterons only got
> cool'n'quiet with the E steppings (also switched to 90 nm process),
> which are brand new and rare.

Opterons grew PowerNow (proper term for the Opteron functionality) with
revision 'CG'.  It just happens that PowerNow supporting BIOS's came out
with the revision E launch [as motherboard vendors had to rev. their
BIOS].

The 130nm -> 90nm was revision D.

 
> Practially every Opteron in common use and currently sold is the C0
> stepping or lower (130 nm) which takes up substancially more power
> than any of the Athlon 64s in the idle case.

Not if you are not using Cool-n-quiet or PowerNow.  A 512KB L2 Athlon64
is of course going to run cooler than a 1MB L2 Opteron or Athlon64 with
1MB L2.  But the Opteron and 1MB L2 Athlon64 of the same silicon revision
has the same heat production.

 
> My socket 754 newcastle 3400+ is one of my least power consuming
> machines when idle, my work Opterons 248 and 250 use a lot more in the
> same situation with the same OS.

You're comparing either a 2.2ghz 1MB L2 or 2.4ghz 512KB L2 CPU with a
2.4ghz 1MB L2 CPU.  Naturally the latter will run hotter and use more
power.  You're also probably comparing revision C0 with revision CG.  (I
can never keep straight the core names, AMD CPU designers and SW
engineers don't use core names as they often are process changes)  You're
also getting more things than just CPU cores involved in your comparison.
2P Opteron boards have more functionality, more power planes, most likely
less efficient power supply, etc...


> If you have two Opterons in one box
> this becomes uncomfortable quickly.  If you get a venice or San Diego
> core (Athlon 64) you are even better off (in that case idle and busy).

I have to disagree - my workstation at both home and work are
dual-processor Opterons.  They don't run uncomfortably hot.

-- 
-- David  (obrien at FreeBSD.org)