• Please review our updated Terms and Rules here

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.
 
czunit said:
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.
Click to expand...

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!

czunit said:
Thanks for posting and buying it. I owe you $100 for this knowledge.
Click to expand...

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
 
Well, I finally got a RAM tester from the guy in the UK and loaded up my working-as-PMI clearpoint board with a full load of RAM. Popped it in, fired it up and....

rmd.jpg

Look at all that free MEMORY. Board is working fine, green lights, all good.

Next up I'll test the memory on my other 4mb board and see if I can find a bad chip. It works fine in Q22 mode, has a yellow light when in PMI mode which turns red when it hits a memory failure. I think it's a bad pair of chips that works when it's running as 16 bit memory but fails when it does the 32 bit reads for PMI protocol.

TALOS works pretty well, been turned off for a year and while the RD54 drive made some odd seek noises on startup it quieted down and is working. A 70% cache hit rate fixes a lot of the slow performance of a MFM/RQDX3 disk.

Maybe if I get the other board going I can see about expanding the pdp11 to 8mb memory :)
 
Darn. Tested the older board with 2mb of tested memory, plug it in board goes red flash, green, then yellow. Fails. Put it in a Q22/CD slot under the CPU and works properly.

I guess one of the PMI driver chips was fried in the past. I'll look at the schematic and see which PMI pins overlap with say 12 volts then see if I can trace it to a chip. Meantime I'll load it to a full 4mb memory and benchmark it against a MSV11-QD (4mb Dec memory with parity only).

Worst case I can still try out running two of these in a single system and play with the memory window concept. XMS for a pdp11.....
 
You must log in or register to reply here.
Back
Top