jnc at mercury.lcs.mit.edu
Thu Jul 11 13:31:41 CDT 2019
> From: Eric Smith
> two separate backplanes that are combined for the RH20s (if
> present), one backplane for the A through D positions (upper 2/3 of
> each module slot), and one for E and F.
How odd. DEC was quite happy to do hex backplanes elsewhere, and it looks
from the photo (EK-108OU-PD-002, pg. 3-8) like the MASSBUS connector are
wired to both backplanes, so they had to stay together.
>> On the -PA to -PV upgrade, could the backplane really be done with
>> some wraps? I ask because I saw in one manual, talking about a
>> KL10-C to -PV upgrade, it calls for a backplane swap-out.
EK-0KL20-IN-001 ("KL10-Based DECSystem-20 Installation Manual"), in
Section 10.2 "KL10-PV Upgrade Procedure for KL10-C", if anyone wants to
> I'm not entirely sure, so I easily could have been mistaken. I know
> -PV to -PW just needs some wraps. -PA to -PV may have required more
> significant backplane changes. Definitely they have different part
> numbers for the -PA and -PV backplane assemblies.
Yeah, DEC was quite happy to have the FS guys do wirewrap on install (e.g.
for the NIA20). So my guess is that if the default upgrade for at least
one -PA to -PV (above) was to replace the backplane, that would have been
the standard way, because of some issue.
Whether it was just too many wires to do manually, or if there were also
trace issues, it would be interesting to know. Oh, it's also possible that
since the -PA to -PV involved a faster clock, I wonder if some backplane
lines turned into twisted pair, or coax?
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