Sherlock Holmes logic
Quote from PBL [Feb26/08:29]:
The 8086 was a 16-bit architecture in which all processing and all data channels were 8-bit. It means you had to do everything twice: once for the lower half and once for the upper half of the 16 bits. The 80186 had full 16-bit data paths and processing.
[Unquote]
Many thanks for the links re the "Viper" chip in 1990, which I'll do my best to read later.
My post was based on information (by an engineer that played leading roles in both 8086 and 80186 design) that, notwithstanding what you have said, the 80186 CPU design was "deeply derivative" of the 8086; the changes being mainly in the "integrated peripherals". Once the 80186 had been out for a couple of years, the chances of undocumented bugs was "pretty darn low".
This thread is so much better debated than its immediate predecessor – thank goodness – even though theories are still revolving almost entirely around semi-informed minutiae of H2O and the B777 fuel system. The discussion of FBW computer architecture is, on the face of it, entirely off-topic.
No one is suggesting that there was a flight-control problem on BA038. But discussions in this area – by the like of PBL, bsieker, 3db, Green-dot, and ve3id – have given us non-engineers a fascinating insight, and could yet read across to the engine fuel system, if not the aircraft fuel system.
Perhaps you guys should all meet with 3db in the UK! So far, the arguments have mainly related to what we ordinary mortals might think of as hidden potential anomalies in logic. Apart from a few anecdotes, little attention has been given to the possible effects of EMI...
Quote from 3db [Feb26/13:22]:
Evidence of a source pointing in that direction is positive logic. How about negative logic? If, I repeat, if, the AAIB can’t find the positive source, then should they consider EMI (and other) sources? It is clear from the AAIB information so-far (in laymen’s terms) fuel that met the spec did not get to the engines when the computers requested more and it was available on-board. Usually, the fuel system works well, but on this occasion it did not perform as expected. In the absence of other sources being positively identified, I would say that is a classic case of EMI awaiting investigation.
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Let's hope it has not been (awaiting).
Last edited by Chris Scott; 26th Feb 2008 at 15:02.
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