On 5/19/2006 10:45 AM, Philip Gust wrote:
> The only problem encountered was that our custom adapter cable was
> wired backwards, so key0 registered as key4, an so forth. The cable
> was built from Xerox Alto schematics, and we need to determine whether
> the problem was how the cable was wired or the schematics. In any
> case we were still able to complete the tests, and we can easily
> rewire the cable to set things right.
Here is a possible explanation for this discrepancy -- (01)
The Alto, like most machines designed at Xerox PARC, was a big-endian
machine. It was PARC custom to number bits on such a machine
left-to-right, so that the high-order bit is numbered 0. This is in
contrast to today's almost universal industry practice of numbering bits
right-to-left, so that the low-order bit is numbered 0. This might have
caused confusion in interpreting the Alto schematics. (02)
Ed Taft (03)
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