[ExI] Why space tech isn't cutting edge

spike spike66 at att.net
Mon Nov 19 14:20:17 UTC 2012

.... On Behalf Of BillK
Subject: [ExI] Why space tech isn't cutting edge

>...Did you know that after a special upgrade Shuttle flight the Hubble
system is now run by a 486 chip?




Ja, I was on a team which did a lot of experimentation with the 486 for
space use.  It is better suited for that purpose than most anything that
came after it, because of its heat generation characteristics and its
feature size, which is enormous compared to what we have now.  This large
feature size makes it far less susceptible to what we used to call RISEUs,
or radiation-induced single event upsets.  This is where a cosmic ray causes
one bit to flip.  All pentiums (pentia?) we ever tested were all messed up
by RISEUs, but the good old 486 would survive.

My contribution to all this is in developing a silver filled epoxy material
which conducts heat from the periphery of the chip into the circuit board so
you can attach a heat-sink on the underside.  All this was in the 1989 to
1992 timeframe.  Also, the 486 is very forgiving if you want to underclock
it to keep it cool.  Also there is a lot of space flight control software in
existence for that chip, meaning it is software that is sufficiently tested
and documented so that it will not crash and kill you up there. 

Also, we preserved a few thousand 486s, anticipating future use, and still
have them. 

Fun days!


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