Steve Toner
Experienced Member
Watch out - from uNote #028 (http://www.ibiblio.org/pub/academic...hardware/micronotes/numerical/micronote28.txt):
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DEC units on ebay
- Thread starter Hugo Holden
- Start date
Watch out - from uNote #028 (http://www.ibiblio.org/pub/academic...hardware/micronotes/numerical/micronote28.txt):
Well, sort of. I have tried it and found that when running a controller in burst mode DMA that the MSV11-JB *can* corrupt PMI IO transfers in memory and lead to RSX11M+ crashing in a spectacular fashion. Turn off burst mode (on my MTI ESDI controller) and the problem seems to go away (but the system is a good bit slower which defeats the whole purpose)
However if you move the memory under the CPU (so it's just normal Q bus memory) it seems to work fine as you're just doing normal good old fashioned Q Bus memory protocols.
My guess is the 11/84's Unibus map doesn't do burst mode on the Q bus side and thus doesn't hit this bug. When they released the 11/83 they went oops, and fixed the issue.
However if you move the memory under the CPU (so it's just normal Q bus memory) it seems to work fine as you're just doing normal good old fashioned Q Bus memory protocols.
My guess is the 11/84's Unibus map doesn't do burst mode on the Q bus side and thus doesn't hit this bug. When they released the 11/83 they went oops, and fixed the issue.
Steve Toner
Experienced Member
Correct me if I'm wrong, but it's my understanding that there's no such thing as a PMI IO transfer (in a Qbus system - I don't know about the 11/84). The PMI bus is only between the processor and memory, and all DMA goes over the Qbus. So it shouldn't matter to IO devices which side of the processor the memory is installed on. Did you reenable burst mode when you tried moving the memory?
I don't think it's a bug or an 'oops' - it's simply that for the 11/84 it was not a requirement, so the earlier boards were designed to meet the requirements of the 11/84 and then at some later time the requirements changed.
gwiley
Experienced Member
Wow, you're lucky. I also bought one but paid full price because I was too quick on the "buy now" trigger and didn't happen to notice that there were a ton of them available.
Similar experience though, the board was packed well and very clean, but mine didn't work.
I bought a single M8357 from them a few weeks prior to the big lot becoming available. The cost was a bit lower, also very clean, and did work. I was able to boot OS/8 with it in RX01 and RX02 modes.
thunter0512
Veteran Member
On my board the DIP switches were set wrong, but after setting them to the correct value it booted and ran OS/8 perfectly.
A few months ago I repaired a M8357 and found that Don North's floppy disk emulator is a very nice debugging aid as it tells you what is happening on the cable and you can select the level of detail you want.
Anyway if anyone wants a M8357 then now is the time to get one.
AK6DN
Veteran Member
And if anyone needs an RX01/2 emulator to go with their board, I have lots available at this point (both SMT assembled/tested version or the thru hole PCB/microSD adapter and parts kit).
Send me a DM if interested.
I won that original DECDataSystem310. I’ve been looking for a DEC restoration project so I threw a bid in, fully expecting to lose, I was actually quite surprised when I ended up winning! Oh man, then I needed to go get it though, tempering my elation. Had been trying for a PDP-8 with blinken lights but those seem out of my price range so this will do, especially since I needed a DEC terminal.
Road trip ended up being a 30 hour drive (round trip) over two days a couple weekends later. Pretty brutal, I don’t want to do that again any time soon.
Interestingly, I checked with the seller on the missing controller card before bidding and he said he had it/would be included, so it pays to inquire. A standup seller too IMO, came in on a Sunday morning and even helped me load, which took about 3 hours since I had to break it down somewhat into manageable sized pieces. I made the solo trip in my pickup truck and that equipment is quite heavy, so I was grateful for the help. I also had the opportunity to look around a bit and there were some VERY interesting things to see. I won’t say more out of respect for privacy but lets just say I’m bookmarking this seller. :D
I did end up buying a DECWriter II while there, which appeared to be still on the original shipping palette. No keyboard though, I think I lost out to you on that one Chris.
Printer inside looks immaculate:
Someone asked about memory; it appears to have one 4K core (yea!) memory board H219A (but also drat, the original sticker said it should have TWO of those) and that white handled mystery card, which I think is 4K RAM, and which may have replaced that second core memory board for some reason?
Lots of 7744s:
Overall I’m satisfied, it’s in good shape for the age and I think it’ll be a fun restoration attempt. I was hoping to score some software for the DEC too while there, but unfortunately that didn’t work out. Lots of documentation though. Once I get it running maybe I can work with folks here on the boot media front. Really curious to see what might still be on that 4K core memory.
cchhrriiss11
Experienced Member
Welcome to the Forum!
Congratulations! Glad that you made it to the forum here, I was wondering who bought the other one! Yes, the DECWriter II is indeed New-old-stock, mine was still in "as left the factory" condition, complete with the feet still in a little bag inside the machine. Mine's the same as yours (sans keyboard), it's technically a LA35 (RO version of the LA36).
Everything that the seller (Blake) has there is in very, very good condition. The DEC 'Classic' that I got is also like-new with little signs of use, no dust inside even! It came complete with no evidence it has ever been worked-on or modified in any way over the years (other than the addition of the semiconductor memory board) -- super happy about that.
Speaking of the memory board, mine has the same one that your's does -- it's a Monolithic Systems Corporation Monostore V (303-0112-000A), I've attached the documentation to this post for your reference.
As for other interesting items -- Indeed, he's got quite the collection. I've since bought quite a few other items from him (bunch of VT52's, VT05, complete DECMate setup, etc) and am extremely pleased with the condition that everything is in.
As for my DEC Classic, I've posted a few photos of it, the VT50-HA and the DWII on my Twitter account:
Here's an inventory of the cards:
On another note, I believe I've got at least one floppy disk that goes with your system (DDS-310 / COS-310) that should be bootable.
My system came with with the documentation, I've since scanned it and sent it over to Al at Bitsavers:
Have you had a chance to power-up / test the terminal yet?
Feel free to send me a PM to keep in-touch!
-Chris
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Wildfire
Experienced Member
@cchhrriiss11
Chris,
Twitter links are only useable for people who have an account, login needed to view.
IDK when that was changed but i assume during the Musk times...
Chris,
Twitter links are only useable for people who have an account, login needed to view.
IDK when that was changed but i assume during the Musk times...
cchhrriiss11
Experienced Member
Thanks! I just noticed that, what a pain! I've removed all the links other than the main one and attached a few photos instead.
Unfortunately Twitter is not what it used to be...
-Chris
I need a few more posts under my belt before I can DM anyone, but thanks for the info. I haven’t had the chance to try the terminal yet, all of the keys stick in the down position when pressed so I have a bit of work to do first cleaning up the keyboard, need to research what the best approach is there.
Well, that clearpoint memory I bought on Ebay works.... sort of.
There are no manuals for this board anywhere but it's a 4mb board with parity that also should run in PMI mode. However when I got it the board tests out fine as normal Q22 memory but not PMI.
Plugging in all the PMI specific jumpers results in a board that fails memory tests when used as PMI and works fine as Q22. I pulled all the 256k chips and tested them in a Pro/350 and they are fine.
So my guess is someone plugged it into a Q22/Q22 bus with all the jumpers in, blew something up, and removed the jumpers.
I'll keep it, though spending $300 for a 4mb board is a bit pricey. And it *does* work. Still, this is one of the first times I have gotten a dud on Ebay.
Oh well, I'm just going to convert my 1mb PMI J board to a 2mb board. How? I will pillage another 2mb board, unless someone knows which chip was different from an 11/83 and an 11/84 memory board.
There are no manuals for this board anywhere but it's a 4mb board with parity that also should run in PMI mode. However when I got it the board tests out fine as normal Q22 memory but not PMI.
Plugging in all the PMI specific jumpers results in a board that fails memory tests when used as PMI and works fine as Q22. I pulled all the 256k chips and tested them in a Pro/350 and they are fine.
So my guess is someone plugged it into a Q22/Q22 bus with all the jumpers in, blew something up, and removed the jumpers.
I'll keep it, though spending $300 for a 4mb board is a bit pricey. And it *does* work. Still, this is one of the first times I have gotten a dud on Ebay.
Oh well, I'm just going to convert my 1mb PMI J board to a 2mb board. How? I will pillage another 2mb board, unless someone knows which chip was different from an 11/83 and an 11/84 memory board.
cchhrriiss11
Experienced Member
I just sent you a DM so that we're connected.
The keyboards on the VT5x terminals are a similar mechanism to what's on the VT05, VT10x, DECWriter II, III, etc -- I've often (incorrectly) called them "Stackpole", but more correctly they're "Hi-Tek" key switches. If the keys are sticking, the "plungers" are probably cracked at the top corners. This is an extremely common issue. I've been replacing mine with ones from a donor keyboard. There's also some "collars" that you can 3D-print that may help as well (although I haven't tried this myself, yet).
3D Printed Collars:
https://deskthority.net/viewtopic.php?t=20317
Key-cap removal tool:
(these can be found all over, but here's an example)
More Information on Hi-Tek Keyswitches:
Hi-Tek High Profile - Deskthority wiki
One of the VT52's that I got recently had to have about 80% of the plungers replaced, whereas the rest of the terminals only had the odd cracked/sticking plunger (lucked-out, for now, I guess).
-Chris
1944GPW
Veteran Member
Please don't throw the broken plungers out. I believe I might be able to repair them - possibly stronger than original, but no guarantees - if I could get hold of a few to test my claim. I would post them back to the sender.
cchhrriiss11
Experienced Member
1944GPW
Veteran Member
Yes please. Half a dozen in varying conditions from slightly cracked to the most broken one would be great.
Do you have a feeler gauge (as used for spark plug gapping)? I'd like to know the clearance between the plunger and the housing on a good key.
I'll PM you my address if that's ok?
Do you have a feeler gauge (as used for spark plug gapping)? I'd like to know the clearance between the plunger and the housing on a good key.
I'll PM you my address if that's ok?
at: DEC PDP-8/L Computer For Parts Only
$14,995. seems a bit optimistic for an 8/L that's had such a hard life.
Parts Only
thunter0512
Veteran Member
It is advertised as "not working" and "It is dirty, dusty, stained, rusty, marks, scratches, mice have been inside of it. The key turns and is Rusty and bent. Missing two of the front colored switch controls. Missing screws for the outer case."
I wonder if the mice are included.
Ebay at its best.
daver2
10k Member
They are not really justifying the 15k price tag are they!
But they are taking offers... How much does rust weigh in these days I wonder!
Dave
But they are taking offers... How much does rust weigh in these days I wonder!
Dave