[Beowulf] power usage, Intel 5160 vs. AMD 2216

[Donald Becker]

On Tue, 10 Jul 2007, Jon Bernard wrote:

> Vendor A estimates that at peak load a compute node with two AMD 2216s,
> 4 GB of 667 DDR2 RAM, a hard drive, and an IB board will draw 265 watts.
> Vendor B estimates that such a node will draw 450 watts.

Considering that the regular 2216 is 95W peak (the 'HE' version is about 
65W), and the memory and IB card are both pretty warm, 265 watts is 
unrealistic.  Multiply a realistic max power by a power supply 
efficiency and you'll get about 450 watts.

There is way to get that lower number: 2216HE processors, and very efficient 
(93% would be exceptional, high 80s more realistic) power supplies.  But 
that will be significantly more expensive.  Easily enough $$ that you would 
know if that's what you are buying.  (We use 'HE' processors, special 
memory and highly-efficient power supplies in our blade systems to make 
the thermals work, and system price/MIPS looks pretty bad compared to 
standard 1U products.)

The chipsets and base processors are same between vendors, and the IB 
cards and disks are about the same.  The memory power use will vary a bit, 
but you might get different numbers between the sample and shipped nodes.  
The biggest variation will be the power supply efficiency.  And even there 
it will be vary significantly with the power draw.

We've measured between 50% and 93% efficiency.  The worst are the supplies 
in old generic 1U cases, which hopefully we won't see again. There is 
a significant cost difference between today's low-end, low-efficiency 
supplies and the better 80+% units.  Doing an extra conversion e.g. to 
50VDC then to the final board voltage, won't improve the 
overall numbers, but will move the conversion and thermals to "behind the 
curtain".

We could get into an interesting discussion about the best way to decrease 
the typical power use of a cluster.  The best way to do this is with 
software -- laptop-style power control, and powering nodes down.  But when 
purchasing and installing clusters you have to design for that 
long-running job that stays at the peak power draw and thermal state of 
the cluster.


-- 
Donald Becker				becker at scyld.com
Penguin Computing / Scyld Software
www.penguincomputing.com		www.scyld.com
Annapolis MD and San Francisco CA