Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@zoo.toronto.edu (Henry Spencer)
Subject: Re: New (!?!?!?!) Shuttle Computers
Message-ID: <1991Mar12.002304.13799@zoo.toronto.edu>
Date: Tue, 12 Mar 1991 00:23:04 GMT
References: <1991Mar7.142311.10412@vaxa.strath.ac.uk>
Organization: U of Toronto Zoology

In article <1991Mar7.142311.10412@vaxa.strath.ac.uk> cabp10@vaxa.strath.ac.uk (Theora Jones, In Person!) writes:
>... I would expect radiation hardened processors, of an industry sstandard
>type (80x86, or 680x0 series) for easy replacement...

Do remember that this hardware was designed in the mid-70s; the processors
you mention did not exist then.  And I'm not sure what you mean by "easy
replacement", given that rad-hardened processors are usually single-source
items even if the architecture is in wide use.  (There *is* one significant
advantage of using something standardized:  the ability to use commercial
hardware for development.)  In general, it's clear that the computers would
look very different if they were being designed today and the software was
being rewritten from scratch.  Those conditions do not apply.

>... if in 1991, the leading manufacturers of semiconductors can
>put upwards of 10^6 transistors on a chip, but can't make radiation resistant
>store...

Rad-hardening is a very specialized business that is not likely to attract
manufacturers who specialize in mass production of commodity parts.  DRAMs
are the ultimate in mass-produced commodity parts.
-- 
"But this *is* the simplified version   | Henry Spencer @ U of Toronto Zoology
for the general public."     -S. Harris |  henry@zoo.toronto.edu  utzoo!henry