[Beowulf] Interesting google server design

Robert G. Brown rgb at phy.duke.edu
Fri Apr 3 06:14:37 PDT 2009

On Thu, 2 Apr 2009, Greg Lindahl wrote:

> On Thu, Apr 02, 2009 at 10:11:07AM -0400, Prentice Bisbal wrote:
>> Or it could be because they make motherboards that convert 12 VDC to 5
>> VDC on the motherboard.
> All Itanium and some other x86 boxes take a single 48V input to the
> mobo. I talked to a mobo designer once and he claimed that there was
> no power savings to be had doing this. Beats me, mon.

There are actual antiadvantages, errm, disadvantages to doing this.

   a) It's a lot easier to kill yourself with 48V than with 12V or 5V.
Easier to arc over and start fires.  I wonder if it is 48VAC or VDC,
too.  Do they use an actual transformer to convert 480V to 48V and then
run the motherboard from that?

   b) The idea is to get the heat production OFF the motherboard.  One
really interesting thing about the google design is that they hang the
stock OTC power supply off the back, altogether outside of the case and
where (I'm going to presume, as I couldn't really make it out in their
design) it fits moderately snugly into a vent to exhaust the heat.

Why would somebody want to pay conversion penalties twice and step down
to 48V once and 12/5 on the one piece of hardware you're committed to
keeping cool?  Maybe Jim has a clue -- he tends to be more in tune with
this sort of madness than I am.


> -- greg
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Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu

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