Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!rochester!cornell!batcomputer!pyramid!voder!apple!bldrnr
From: bldrnr@apple.UUCP
Newsgroups: comp.misc
Subject: Re: IBM mainframe for sale
Message-ID: <6405@apple.UUCP>
Date: Fri, 2-Oct-87 00:28:54 EDT
Article-I.D.: apple.6405
Posted: Fri Oct  2 00:28:54 1987
Date-Received: Sat, 3-Oct-87 09:14:54 EDT
References: <4WALT@MAINE> <177200006@uxc.cso.uiuc.edu> <14944@watmath.waterloo.edu> <4673@nsc.nsc.com>
Reply-To: bldrnr@apple.UUCP (Brian Hurley)
Distribution: comp.misc
Organization: Apple Computer Inc., Cupertino, USA
Lines: 36
Keywords: Cray...

In article <4673@nsc.nsc.com> woolsey@nsc.UUCP (Jeff Woolsey) writes:
>In article <14944@watmath.waterloo.edu> ccplumb@watmath.waterloo.edu (Colin Plumb) writes:
>Cray power is 400Hz, for one thing.  This means a motor-generator, and
>you usually don't want those things where anyone can hear them, which
>means a separate room for them.
 
  Cray power, if I remeber correctly is motor-generated for isolation reasons
rather than any need for transmission.  As it turns out a Cray needs on the
order of 15KW source.  This can only be supplied by a main feed of some kind
from a power company main.  Which is 400hz 3-phase(?).

>Cray cooling uses water or freon (I forget which) pumped through the
>aluminum columns.  This fluid then goes through a fairly large heat
>exchanger.

	Freon.  One interesting note on the cooling system for Apple's XM-P:
	It is whisper quiet.  The Cupertino neigborhood next to the building
	that houses the Cray is about 50 yards from the 'containment building'
	the most incredible aspect of this is that from outside you would never
	know that there was a 12 ton throughbred roaring away in side.
	   1 meter of high density acoustic insulator did the trick.
	All the way around the back room where the freon pumps and water heat
	exchanger were...including the MASSIVE doors to the outside world.
	   When I got a tour of the machine I found out why the computer was
	so well isolated from tender ears... The only thing I have to compare
	the sound of 4(6?) motor-gen to is jet engines at *close* range.    
	It might have been the acoustics of the room, but GEEZ that stuff is
	loud!

	--/--bldrnr--> @apple.UUCP