Newsgroups: bit.listserv.words-l
Date:         Mon, 14 Dec 1992 18:27:55 EST
From:         Tony Harminc <EL406045@BROWNVM.BROWN.EDU>
Subject:      Water Cooled Computers
Comments: To: words-l@uga.cc.uga.edu

Posted on 14 Dec 1992 at 11:44:46 by Frank Peters

>: What is a chilled water system, btw?  Do IBM mainframes have cold water
>: running through their innards?  Maybe the water got too cold and froze
>: the listserv.  I would say it's time for UGA to be back up.  It still is
>: not answering to 'ping', alas.
>
>IBM pig iron is water cooled.  Yes, the cold water runs through their
>innards.  Quite an impressive amount of it actuallys.  Its one of the
>many things that make the beasts so expensive to run.

Sigh.  Mainframe Myth time again.

Any device that is electrically powered converts most or all of that
electricity to heat.  If the heat is not removed somehow, the device's
temperature will rise until it eventually melts.  This applies to lightbulbs
and waffle makers as much as to IBM mainframes and Sun Sparcstations.
In the case of lightbulbs and waffle makers, the cooling is accomplished
by natural air movements.  Once the device reaches a certain temperature,
the heat is transfered into the surrounding air.  Typically this temperature
is quite high - much too high for a computer chip to run at without damage.
The efficiency of heat transfer can be improved in two ways: blow the air
at the hot parts, or use a coolant with a higher specific heat - e.g. water.
PC's use the first scheme (a fan); large mainframes the second.

Water cooling for computers has the obvious disadvantages that it requires
plumbing inside the machine, and a supply of cold water from somewhere.
Clearly it would be ridiculous for a PC.  But for a machine in a
computer centre or indeed in any large building, it makes great
sense.  These buildings almost always have central air conditioning
in any case, and central air conditioning involves, by definition, a
central plant that cools water and pumps it around to the various parts
of the building where heat needs to be extracted.  Usually the heat is
in the air inside the building (from people, lights, motors, and of course
air cooled computers).  The heat is transfered from the air to the cold
water which is then sent back to the plant to be cooled off again.  Pumping
a little of the cold water through pipes inside the computer itself makes
for greater cooling efficiency and lower cost.  It also allows higher
density of components which translates to higher speed.  All very fast
computers are liquid cooled.  The fastest (e.g. Crays) use Freon (CFCs)
instead of water.

The argument that water cooling is expensive is often made by those
who don't have to pay for the costs of cooling their little air-cooled
machines.  This doesn't mean that it's cheaper - just that the cost
is distributed and no central authority ever notices the bill.  The
same is true of the power costs, of course, and often the support too.

>I guess I'll have to dig up Bill Joy's quote about ancient dinosaurs
>with bodily fluids being pumped from a semi trailer.  He was talking
>about an IBM at a UNIX conference.

Any fool (particularly a partisan one) can compare apples and oranges.
Comparing an IBM mainframe of ten years ago to his latest workstation
is nonsense.

Tony H.
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