MM11-U/UP core memory backplanes
jnc at mercury.lcs.mit.edu
Sun Feb 28 11:37:05 CST 2016
> From: Bill Degnan
> Very useful, thanks.
Eh, de nada - glad to help contibute to the knowledge base.
> I will try this.
With MM11-U gear, or MM11-L?
I ask because, like I said, I still don't have 100% clarity on the MM11-L
situation. I am pretty sure there are old MF11-L backplanes that can't be
upgraded to parity this way (i.e. removing the jumper), and may not be
upgradable to parity at all (i.e. it might take etch cuts that are
'impossible', if they are on the bottom side of the PCB).
There's that jumper that should be there on non-parity units, but does not
seem to be there on some older backplanes (so you can't remove it to make the
backplane parity-capable); arguing that it's probably hard-wired in the etch
on those older backplanes? And there seem to be a couple of pins that need to
be bussed acros, for the MM11-L units to 'talk' to the parity controller. And
if the parity jumper isn't there, logically those bussing etches might not be
there either. So I have a little work ahead of me with an ohm-meter...
Speaking of the jumper, and bussed signals: the parity board input pin that
that jumper is connected to (when the parity board is not there) must be
bussed to all three group locations in the MF11-L backplane, as a wired-OR of
their proto-SSYN outputs. If it were daisy-chained among the three groups,
you've have to put the board sets in in a specific order, no? (Otherwise a gap
would lose the signal from the group(s) on the far side of the gap.) And
there's nothing like that in the manual. Something else to check out on the
prints and/or with a meter..
Anyway, please report back on your experiences, so if there's any useful
info you pick up, we can learn from it.
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