UNIBUS extension card/cable sets
paulkoning at comcast.net
Thu Jun 25 13:06:46 CDT 2015
> On Jun 25, 2015, at 2:01 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu> wrote:
>> From: Paul Koning
>>> Right, but the very similar QBUS does have terminations (of a sort -
>>> the rules for when you need terminations on QBUS extensions are so
>>> complex that I don't really grok them yet) 'in the middle'
>> That doesn't seem likely. ... the definition of 'termination' is
>> something that you learn in EE 101 and are unlikely to forget.
> I agree with your sentiments, _but_ all I know is that if you look at,
> e.g. the 1982 'microcomputers and memories' handbook, pg. 251, you'l see a
> three-backplane system, with terminations at the start _and_ end of the first
> backplane (and also at the end of the third backplane).
What’s between the backplanes? If it’s a repeater, that would be correct (because you have two separate transmission lines). If it’s a cable, then this is wrong. But as Tony said, it might be that it’s not so wrong that things break, thanks to the small scale and slow speed of Qbus.
More information about the cctalk