test-drb April 2020

test-drb@ccmp.vtda.org

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by couryhouse＠aol.com

4 years, 7 months

Bob Davis and old computer stuff

by cz＠alembic.crystel.com

Hi! Does anyone here remember Bob Davis? C

4 years, 7 months

Bob pictures from 2005, it's like the titanic....

by cz＠alembic.crystel.com

The outpouring of messages and help has been quite inspirational. It seems that the Perq data is really important, so I will be going back today for a bit to try and get the boxes of data tapes out of there. DC600's, I'm sure they will need to be restored somehow but I'll try to get them. In the meantime here are 4 pictures from 2005 of the stash. To be honest almost nothing has changed between then and now, it was like looking at pictures of the titanic from 1912 and today. https://www.crystel.com/bob/bob%201.jpg https://www.crystel.com/bob/bob%202.jpg https://www.crystel.com/bob/bob%203.jpg https://www.crystel.com/bob/bob%204.jpg Chris

4 years, 7 months

pdp11/84 PMI memory: What is the problem with Q bus?

by mark＠matlockfamily.com

> I actually have -B/-C boards, I should plug one in in QBUS mode, and get my > QSIC prototype working again (it somehow random failed during the last year, > and I've been too lazy to debug it), and write a little program to DMA blocks > in and out, and see what happens to the data. If I get really energetic I > could throw a 'scope on the bus and look at bus cycles and see if they look > OK. > > It would be interesting to have some more detail on the failure. > > Noel Noel, The experiments you describe above would be very interesting! In the accidental tests I did using -C boards in an 11/83, RSX booted ok and ran for a good bit but I think errors Started to accumulate due to bad DMA writes that either were written to the wrong logical block Or the data written was scrambled. When this happened on my BA23 11/83 I scratched my head Took the boards to a BA123 11/83 and repeated the mistake. Fortunately I use two SCSI2SD devices In each system and leave one identical unit unmounted except during disk to disk backups. With good memory boards I was able to do a disk to disk restore and recover everything up to My last backup. > And that might make sense: PMI memory responds to the Q bus just like > normal memory. So from a Q bus device perspective it's just boring old > memory and thus no speed improvement. What might speed up is if I did > memory to memory (VM0:) copies, but with only 2mb running at the moment > there's not a lot of time to check for performance differences. Chris, I think the way that you see the biggest performance improvements in PMI over Q22 memory Is when you have heavy asynchronous I/O happening at the same time the CPU is compute bound And the memory access is not well cached due to the type of programs being run. This is more Likely to happen in a busy multi-user environment. RSX has a tool IOX that was developed to load a RSX system and simulate multiple users. The CPU can get at memory via the PMI and not be delayed Waiting on the Q22 bus. This is particularly helpful with larger block mode Q22 transfers that don?t cause CPU memory access delays. Mark

4 years, 8 months

Dixie Canner CPT 8000?

by anders.k.nelson＠gmail.com

https://www.ebay.com/itm/143536589578 What in the world is this?

4 years, 8 months

pdp11/84 PMI memory: What is the problem with Q bus?

by jnc＠mercury.lcs.mit.edu

> From: Mark Matlock > Are you able to use a Qbus MTI controller in the 11/84's Qbus section > of the backplane? This is something I've often wondered about but never > tried. I looked into this in some detail, but I don't know: https://gunkies.org/wiki/KTJ11-B_UNIBUS_adapter#QBUS_slots Amswering it definitively would probably require looking at DMA and interrupt cycles with a logic analyzer on the bus, to see what the CPU does with them. And the KDJ11-B and KDJ11-E (the 11/94 uses the same bacplane with a different CPU card) might act differently. > For anyone who is curious about what Happens when a M8637-C version > board is used as PMI memory in an 11/83 I can speak From experience. > ... > After this the disk is corrupted and you will need to restore the > system disk from backups Ah, very informative; thanks for reporting. So whatever the fault is (perhaps the QBUS block transfer issue reported up-thread), it must _seem_ to work, but fail in actuality. It would be interesting to appply a logic analyzer, and see what the bus transaction looks like, if it looks OK on the bus (in which case it's an internal failure). Noel

4 years, 8 months

pdp11/84 PMI memory: What is the problem with Q bus?

by jnc＠mercury.lcs.mit.edu

> From: Jerry Weiss > Sorry about the uNOTE confusion.. No problem, it only took me about a minute to find the right one; my note was to warn other people who didn't know about the number duplication. > If you look at the Memory Comparison table in this OEM uNOTE, it only > lists Block Mode for "JD/JE ONLY". Oh, right. Still, it sounds from reports here like regular DMA doesn't work in QBUS mode either - and technically that table entry might mean than since it doesn't work for the QBUS _at all_, that includes no block mode. I actually have -B/-C boards, I should plug one in in QBUS mode, and get my QSIC prototype working again (it somehow random failed during the last year, and I've been too lazy to debug it), and write a little program to DMA blocks in and out, and see what happens to the data. If I get really energetic I could throw a 'scope on the bus and look at bus cycles and see if they look OK. It would be interesting to have some more detail on the failure. Noel

4 years, 8 months

pdp11/84 PMI memory: What is the problem with Q bus?

by jnc＠mercury.lcs.mit.edu

> From: Jerry Weiss > uNOTE # 028 indicates that MSV-11 JB/JC (M8637-B/C) doesn't do block > mode. I went and looked at uNOTE #28, after I found it (it's not in the initial set of uNOTEs, but in the second set - the so-called 'OEM uNOTEs"; note that the numbers were re-used between the two sets, so there are _two different_ uNOTE #28's). I couldn't find anything there about the JB/JC not doing block mode? All it says is they "can not be used in a Q-BUS system due to gate array incompatibilities". Noel

4 years, 8 months

pdp11/84 PMI memory: What is the problem with Q bus?

by jnc＠mercury.lcs.mit.edu

> From: Chris Zach > Just checked the configuration and block mode DMA *is* off. Interesting. So it's not bklock-mode on the QBUS which is screwed up, but normal QBUS transfers. That jibes with the comment abour "gate array incompatibilities" (which I take to mean "errors" :-). > was the 11/70's MASSBUS channels nothing more than RH11-C's attached to > the old FASTBUS on the 11/45 cpu core (which is what an 11/70 really > is, with cache) or did they port right to the memory box? RH70's are totally different from RH11's - a hex card, and a couple of quads - and the interface to the /70's memory system is totally different from the RH11's (which goes to the UNIBUS): https://gunkies.org/wiki/RH70_MASSBUS_controller It has interfaces to both the cache, and the memory bus (although the diagram in the 11/70 CPU handbook shows it as only connected to the cache). I didn't follow the "the old FASTBUS on the 11/45 cpu core (which is what an 11/70 really is, with cache)"; the 70's cache is what's connected to what used to be the FASTBUS, the memory bus connects to the cache, IIRC. Noel

4 years, 8 months

Kennedy 9800 - Power-up tips?

by anders.k.nelson＠gmail.com

Hi friends, Now that I have enough hobby time having quit my job two weeks before the apocalypse, I'm interested in poking at my Kennedy 9800 tape controller project. I bought the tape unit in Q3 2017 and the seller said they had powered it up and nothing seemed awry. I have not powered it up and reading about old electrolytic cap issues I'm curious if I should do anything beyond replace any obviously leaking/ruptured capacitors. IIRC people have used a variac to gradually bring the power supply up to operating voltage and somewhat refresh the capacitors - is this a thing? Is this advisable? Any help is appreciated! -- Anders Nelson www.erogear.com

4 years, 8 months

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test-drb April 2020