6 Oct
2015
6 Oct
'15
9:35 a.m.
Yes, it is a pity that the later board set (a)
has the jumper to
disable the built-in console port and (b) has the switchable divider
allowing higher baud rates so you generally don't need to :-)
Well, except for those of us who don't have any 20mA gear, and want to
standardize on EIA... :-) Adjusting the
RC clock is not hard given a frequency counter, and it
doesn't have to be that precise.
The prints actually give the time for the pulse width on the two different
speed groups, so a well-calibrated 'scope should do it. The grants are
the only (I think) unibus signals to be active high.
Yup. A source of great confusion to me when I started working with the QBUS,
where they are asserted _low_! Interestingly, I think the M9302 was a _later_
solution to this problem in
the 11/34. In the early ones, there's a 'SACK Timeout Module' (M8264) which
I
think performs the same function, but at the _start_ of the bus. (I say
'think' because this module is poorly documented - e.g. I don't know of
anything which definitely states which slot to plug it into.)
I have one of those somewhere.... I remember a 4 bit counter and LEDs, possibly to
count errant grants, but it's been a long time since I looked at those prints too. I
always assumed it went in the last SPC slot, but I am not sure.
-tony