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Clearpoint QED1 4MB Qbus PMI Memory

That.... is interesting. I'll look into the shadow register thing, might point out where my one board that works fine in Q22 but bombs in PMI mode is having problems. Also the chip map helps, and the understanding that it is a 64 bit memory explains a lot of the oddness I was seeing when I was pulling chips to try and map it.

Thanks for posting and buying it. I owe you $100 for this knowledge.
 
That.... is interesting. I'll look into the shadow register thing, might point out where my one board that works fine in Q22 but bombs in PMI mode is having problems. Also the chip map helps, and the understanding that it is a 64 bit memory explains a lot of the oddness I was seeing when I was pulling chips to try and map it.

Yeah I gave up with mapping and put all the chips in an Intel AboveBoard 286 ISA RAM expansion and tested that way -- I was getting nowhere otherwise!

Thanks for posting and buying it. I owe you $100 for this knowledge.

Up to you, I'm still very appreciative of the parts unit RL drive!
 
Hm. That memory banking thing is also quite interesting: Technically you can put 16 of these in a Q Bus system and have a system with 64mb of memory Granted the memory would be kind of like EMS memory on a 1mb IBM PC/XT, but that looks kind of.... cute.
 
The docs also mention this being an ECC chipset Clearpoint came up with, kind of suggesting it was used, or planned to be used, in other products. Perhaps there's something else that uses it on a completely different platform?
 
I recall work looking into an add-on for RSX-11M+ that allowed up to (i think) 16MB RAM on a PDP-11/73 - using certain memory boards with extra paging registers, there was an RSX Guru in the UK back in the 1980s call Adrian Bottoms (yes really - stop that right now) and he came to our office a couple of times to pitch the idea, but we never ended up using it.

Robin
 
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