power consumption

Jim Lux James.P.Lux at jpl.nasa.gov
Tue Feb 20 17:44:51 PST 2001

There is a lot of power consumption data for various form factors at the
Intel web site.(I think it is http://www.teleport.com/~ffsupport/ )

The ATX/ATX12V Power Supply Design Guide on that site  gives the following
"typical" power distribution for a 160W ATX configuration:

+12V  0-6A, 8A pk  (most likely when hard drives spin up, or floppy
+5V    1-18A
+3.3V 0.3-14A
-5V    0-0.3A
-12V 0-0.8A
+5 VSB 0-1.5A, 2.5A pk

They have a nifty little chart showing that the combined +5 and +3.3 loads
share power rating with the 12V.  If you draw the full 72W of 12V, you can
only draw about 30-75W from the lower voltages.

For 200W, 250 and 300W configurations the powers increase a bit:
+12V, 8/10,10/12, 12/14 (max/pk)
+5V, 21,25,30

The spec requires 68% efficiency (which, by the way, is pretty bad), with
some other stuff for "Energy Star" operation

A better guide may be the FlexATX thermal design document, also from Intel..
(This doc has a lot of useful information on airflow and temps within
typical tower cases, etc.)

Processor <=40W
Chipset/Graphics 3W
Mobo Misc 5W
Slot #5, PCI card 5W
Mobile CD ROM 5W
HardDrive 8W (7.2krpm, idling)

Subtotal 74W (DC)
Pwr Supply 32W (assumes 70% efficiency)
Total AC 106W

All temps are specified as Tamb<=55C, except processor at Tinlet = 40C

Another document (MicroATX) mentions 60W for the processor, 11W for the
voltage regulator, 12W for AGP graphics,  etc. for a total DC power of 131W

-----Original Message-----
From: pbn2au <pbn2au at qwest.net>
To: beowulf at beowulf.org <beowulf at beowulf.org>
Date: Tuesday, February 20, 2001 5:13 PM
Subject: Re: Beowulf digest, Vol 1 #279 - 12 msgs

>    Just a question, a thought that came up during the shelves discussion.
Does any body  have a
>web site or other information that would provide me a guess at how many,
and what kinds of
>motherboards I could connect to a single 250W power supply?
>   For instance: A super micro P5STE Running a P 200, 1 floppy drive, a fan
and a nic card. Also
>figure for 64, 128, and 256 meg ram..
>    Power is not cheap but I am! The configuration sets in an old rack
mount , and has 8 fans to
>cool it. Stop laughing and think about it.
>Beowulf mailing list, Beowulf at beowulf.org
>To change your subscription (digest mode or unsubscribe) visit

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