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From: gadbois@geier.philosophie.uni-stuttgart.de (David Gadbois)
Newsgroups: comp.arch
Subject: Re: 64 bits
Message-ID: <GADBOIS.90Aug17183952@geier.philosophie.uni-stuttgart.de>
Date: 17 Aug 90 16:39:52 GMT
References: <5539@darkstar.ucsc.edu> <13285@yunexus.YorkU.CA> <30728@super.ORG>
	<9660@ganymede.inmos.co.uk> <224@csinc.UUCP>
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In-reply-to: rpeglar@csinc.UUCP's message of 17 Aug 90 13:36:42 GMT

In article <224@csinc.UUCP> rpeglar@csinc.UUCP (Rob Peglar) writes:

   From: rpeglar@csinc.UUCP (Rob Peglar)
   Date: 17 Aug 90 13:36:42 GMT

   [...]

   I know quite a few people who would be delighted to have a
   microprocessor that had a 64-bit address (text) space.  They would
   be even more delighted to have a 48-bit or 64-bit data space.  As
   for "ya gotta have the disk to back this", sure, but the cost of
   external storage (non-volatile) - french for "disk" - is falling
   fast ($/GB).  Magnetic media are around $2x00/GB, shop around for
   the best x.  Optical media is following the trend.  Even down and
   dirty DRAM would be (probably) $70,000-80,000/GB; certainly
   feasible for some people.

I have noted this before, but it probably bears repeating:  While big
address spaces are certainly desirable, don't forget that we are
talking about powers of 2 here.  Assuming that media for backing store
costs $1.00 per megabyte, enough to support a full 64-bit address
space would set you back $17,592,186,044,416.00.  A 48-bit space at
those rates would cost $268,435,456.00, and even a measly 40-bit (just
one terabyte) one is over a million bucks.  Media costs are going to
have to drop a lot for really big address spaces to be practical.

--David Gadbois
gadbois@cs.utexas.edu