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From: robison@uiucdcsb.CS.UIUC.EDU
Newsgroups: net.arch
Subject: Re: VERY LARGE main memories: crypt
Message-ID: <5600054@uiucdcsb>
Date: Sat, 13-Sep-86 12:04:00 EDT
Article-I.D.: uiucdcsb.5600054
Posted: Sat Sep 13 12:04:00 1986
Date-Received: Sun, 14-Sep-86 20:12:17 EDT
References: <15505@ucbvax.BERKELEY.EDU>
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Nf-From: uiucdcsb.CS.UIUC.EDU!robison    Sep 13 11:04:00 1986


For the curious, my freshman physics text[1] contains the estimate:

	No. of nucleons in known universe ~ 10^80

This would be ~ 2^266.  Even if a memory this size could be built, there
is still the problem of finding enough power for it.  There are quantum
limits for the minimum power of switching devices[2].   

[1] *Mechanics*, Kittel, Knight, Ruderman, Helmholz, and Moyer. 
    (2nd edition, 1973)

[2] "Physics of Computational Systems, " in *Introduction to VLSI Systems*,
    Mead and Conway, 1980.

Arch D. Robison
University of Illinois at Urbana-Champaign