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Thread ID: 19432	2002-05-15 06:04:00	NASA after 8086 chips	Guest (0)	Press F1

Post ID	Timestamp	Content	User
48949	2002-05-15 06:04:00	I see in the news that NASA is after 8086s. The shuttle apparently still uses the older technology, but they do not seem to have enough spares. All I can say is - they are not having mine. My trusty xt is still working fine thankyou!!!	Guest (0)
48950	2002-05-15 06:29:00	How much are they paying for them? I mean, if they NEED them, then they should pay a premium for them... I've got a few '86s somewhere (dunno where - probably in storage somewhere). Mike.	Guest (0)
48951	2002-05-17 05:44:00	The Shuttle computers don't use anything as modern as an 8086. They were built by IBM, and are super-reliable. Core memory is probably something like 32 kB. They are so small that they can't hold the software for more than one 'phase' of flight, so are reloaded in flight from the reel-reel tape recorders. (To avoid the reels acting as flywheel attitude propulsion units, they are on the same axis and contrarotate. The first flight countdown was held up for some hours while IBM convinced NASA that the computer self-check error could be fixed by turning the computers off then on again. They don't have a ctrl/alt/del restart. (The problem was that the flight control works on a 20 mS tick. On one tick, the sensors send information to the computers; on the next tick the computers send out commands. Somehow, the manual testing in the countdown managed to get the computers and sensors out of synch. They use three computers at once, and they compare inputs and outputs, with disagreement causing alarms. If two agree, the third is told to go away, until a fourth one can be loaded with the appropriate programme and plugged in. This synch problem affected all three, so the countdown panic mode was entered.) A fifth computer is carried --- it is loaded with the reentry and landing programme. If all else fails, it can be plugged in, to get them home. It does *not* rely on O-rings --- even spool drive belts on a tape recorder. I don't know what they would have used 8086 for ... they used some RCA 1802 8-bit micros in satellites and probes, because (with a sapphire substrate) it could be radiation hardened. I have a suspicion that anything as complex as an 8086 (!) could be difficult to 'qualify' for man-flight control.	Guest (0)
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