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MicroSD disk controller for PDP-11


Jun 6, 2020
I vaguely remember that the bus on E85 was the same as on its pro--totype, including even inch based pitch. I might be wrong on that, but E85 is certainly a rare species on this side of the ocean. Pro 350/380 should be much more common

Cool. What part did you plan for physical connector? I realized later after writing that those board have weirdest jaw-pinch connector type. I would certainly be willing to sacrifice my color bit map board to de-solder the original DEC part connector, but that would not be a sustainable plan for a (limited) mass production. The main section of connector seem to be equivalent to ISA-8, but second section is shorter and closer to main than on ISA-16.

That would be very intriguing with respect to existing pro software that was using graphic capabilities of pro. But maybe from the point of view of available software it would better to be compatible with DVK/BK graphics. I was enjoying the native version of LAND for E85 on my 350 though

forced to upset
I do not plan to produce ready-made controllers yet
because in principle I do not know where to get the connectors

also now I do not have complete information on the operation of the bus in DECPro

also I don't have DECPro
i only have E85

i am planning to make PCB for experiments with AZ for firmware development


Experienced Member
Aug 20, 2016
Now that my AZ board for qbus is working I decided to take a closer look at decpro. Specifically, I was curious if some generic female edge connector could be used. Looking through my spare boxes I found what looks like ISA connector. Placing it against decpro board showed the same pitch.
But contact points seemed to be deeper into connector than on the board. So I decided to try it on my machine. Suprisingly, it snapped on quite tight, fitting into the slot without any modifications. I checked continuity on few pins, and it was solid. So looks like it might be feasible to try making ribbon cable from qbus slot to decpro CTI bus using ISA plug and try to make AZ board work there. Well, in my case I think I will make use of my spare DVK bus AZ board, as prospect of building working DVK chassis seem to be quite remote. Here is picture of physical prototype layout sans ribbon cable - note ISA connector in the last slot on the right.
Looking at CTI bus (bitsavers, table on page 5-133 or 183) it seems to have the same set of multiplexed A/D plus same arbitration signals plus some extra signals that seems not needed :). So it might just work. Well, except boot loader I am afraid.