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From: mark@mips.UUCP (Mark G. Johnson)
Newsgroups: comp.arch
Subject: Power vs number of circuits
Message-ID: <732@obiwan.UUCP>
Date: Thu, 1-Oct-87 12:00:49 EDT
Article-I.D.: obiwan.732
Posted: Thu Oct  1 12:00:49 1987
Date-Received: Mon, 5-Oct-87 07:20:56 EDT
Lines: 20

In article <2934@ames.arpa>, lamaster@pioneer.arpa (Hugh LaMaster) writes
	> Current Cray technology is a 250MHz processor.  Try clocking
	> your 68020 or MIPS machine at that speed and see how long it
	> takes to melt.

In the MIPS CPU case, about 3/4 of its 2W power dissipation (at 60 ns
cycle) is due to switching (power = C*V*V*f).  However, assume the worst,
that ALL power consumption is due to switching transients.  Then you
just scale by (60ns / 4ns) and find that its power at 250 MHz would
be 30 Watts.  Since it's now a Cray-class device, it gets to use a
Cray-sized 50 ton refrigeration unit, so 30 Watts should be no problem :-).

Of course, we'd drop to a power supply of 3 volts, in which case the
C*V*V*f power consumption would fall by (3/5) squared, giving 10.8 Watts.
This power level is routinely acccomodated today, in air-cooled
conventional packaging (for example in the larger ECL gate arrays).
-- 
-Mark Johnson	*** DISCLAIMER: The opinions above are personal. ***	
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