> Date: Tue, 21 Apr 2020 16:17:07 -0400
> From: Chris Zach <cz at alembic.crystel.com>
> To: cctalk at classiccmp.org
> Subject: Re: pdp11/84 PMI memory: What is the problem with Q bus?
> Message-ID: <27647f0e-19d4-b484-d288-e9f3bb715363 at alembic.crystel.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Thanks Mark! Actually this was just the boards from the 11/84 (no idea
> what happened to the chassis, drat) so it's an 11/84 CPU (18mhz, FPP
> chip installed), 2 PMI boards (one old 2mb, one new 1mb) a console board
> of some sort and the Unibus map.
>
> I popped this into my BA23 to speed things up a bit in place of my quad
> height 11/73 CPU with 2mb memory. So far it seems to work, and with the
> CA memory in the PMI slot managed to boot RSX11M 4.2 and compile up EMPIRE.
Chris,
I understand now. I also have a PDP-11/83 in a BA123 box and the CPU and
PMI memory (M8637-E) can move from the Qbus box to the 11/84 box and work fine
In either. I spent a good bit of time tinkering with the 11/84 power supply which did not
Work until I put a M7556 minimum load module in it. Basically the +/- 12 Volts needs a
Load or you get a hung bus error. Also, with the Unibus you have to pay attention to
The NPR/NPG grant jumpers.
For disks on the QBus systems I used the UC07 and SCSI2SD. The UC07 can be
can be configured for block mode transfers and I think it is doing it. I guess I?d need
to hook up a logic analyzer to know for sure.
The 11/84 uses a UniBone and when it is emulating a MSCP disk, it can do 150
I/Os a second (using IOX on RSX11M+) The 11/83 using the UC07 and a SCSI2SD
Does about 60 I/Os per second. I think the UC07 could go faster but is limited by the
SDcard interface. I need to put a fast real SCSI disk on it sometime and see what it can do.
>
> My guess is the 11/84's Unibus talks directly to the PMI bus and
> orchestrates the data transfers, but there is something wrong when the
> PMI memory is accessed on the true Q bus. That would not happen on an
> 11/84 (CPU and Map use PMI only) but when you have a Q bus DMA device it
> probably manifests at random. It's possible the MTI card is throttling
> the DMA to single mode instead of hog mode, wonder if I want to screw up
> my disk to verify this?.
What is the model # for your MTI disk controller?
>
> Drat. On the positive side it's chock full of 256k chips, which I could
> pull off and put on the EA board to bring it up to 2mb memory. I have
> air heat tools and a pre-heater so getting the chips off should be
> pretty basic. Getting them on the new board though could be a pain since
> all the holes are soldered over?.
Moving the RAM chips sounds a bit tedious but would certainly be possible.
>
> No way to reprogram or fix it I assume?
Are you asking about making the M8637-B or -C into the -D or -E? If so I?ve
never seen any reference to doing that. I was very fortunate that the person
Who sold me the M8637-C was willing to trade it for a -E.
Mark
Guys,
I got a positive response about the Port-A-Punch cards so no longer any need
to respond to this one. Very encouraging.
Still looking for Jacquard cards and original Hollerith cards. Hope springs
eternal.
peter
|| | | | | | | | |
Peter Van Peborgh
62 St Mary's Rise
Writhlington Radstock
Somerset BA3 3PD
UK
01761 439 234
"Our times are in God's wise and loving hands"
|| | | | | | | | |
Hi all,
was just fishing in old memories & graphics systems. We had in the
1980's a big fridge from Grinnell Systems as a frame buffer on a 11/34.
Anybody remember those? Links to any documentation?
Cheers!
Back in 2013, Bob Rosenbloom asked:
> I have an HP 9872 plotter that just died. According to the internal self
> test (very nice!)
> one of the bib (MOS to TTL) drivers has failed.
Tony Duell wrote:
> the devie is very simple (it's simialr to the 74LS245) but the problem is
that one side of it does not work with TTL levels. It's a level shifter too.
Although the BIB functioned as a level shifter, in later devices using the
1818-2500 standalone 40-pin BPC Binary Processor Chip, including the 9872C
and 9872T, HP actually used the 74LS245 instead of the BIB. The only thing
they did to meet the MOS level input requirements of the BPC was to put a
10Kohm pullup resistor to +5V on each data line on the MOS side of the
buffer.
As noted elsewhere, the 74LS245 isn't pin compatible with the BIB, so an
adapter would be needed to substitute it.
The 9872A, which uses the BPC with the BIB chip, does not have pullups on
the MOS side. It also uses the HP 16-bit NMOS ROM directly on the MOS side,
and it's remotely possible that adding 10K pullups could be a problem with
the ROM.
I am on a mission to fix a bunch of power supplies and now I am looking at
my MicroVAX 3100/95. A few days ago I mentioned that the big smoothing
capacitors on the primary side might need replacing. I have done that now.
However, in doing so, I have discovered that *one* of the capacitors does
not get discharged after the power has gone off (this applies both to the
original ones and the brand-new replacements). Furthermore, after
discharging them with a resistor and checking that the charge had gone,
several hours later, the one that does not discharge, has some charge again,
that was not there before!
Does anyone know if these PSUs have a bleed resistor to discharge the
smoothing capacitors? Why would only one be discharged, is there normally
one bleed resistor per capacitor? Why would the capacitor acquire charge
again when it hasn't been powered on?
Thanks
Rob
Greetings
I went looking for a specific version of C-Kermit to reconstruct sources
for an old system (The Boston Software Works Venix for Rainbow that I
have). I didn't find the 4C(052) I was looking for, but did find many
previous 'presumed lost' versions.
https://bsdimp.blogspot.com/2020/04/finding-kermit-4x.html
has the details.
Of particular note: I got almost all the lost versions off DECUS tapes
hosted in various places because they were copies of the KERMIT tape,
pruned down to just be the DEC stuff. Maybe people here care, maybe not...
Warner
Following on from my previous post re punched cards, thank you for replying.
I am following up where I can.
Now, however, I realize that the IBM Port-A-Punch requires a special type of
cards. Does anyone have 1 to 3 of these they can spare. (I already have the
instrument.)
Many thanks,
peter
|| | | | | | | | |
Peter Van Peborgh
62 St Mary's Rise
Writhlington Radstock
Somerset BA3 3PD
UK
01761 439 234
"Our times are in God's wise and loving hands"
|| | | | | | | | |
The System Source Computer Museum is closed due to COVID-19, so we are making some video gallery talks.
Here is the first one:
https://www.youtube.com/watch?v=hq7aVCc2GP8
The video describes some of the applications of this 57 year old computer including it original use at Goddard Space Flight Center
Bob Roswell
museum at syssrc.comhttps://museum.syssrc.com
> From: Chris Zach
> in place of my quad height 11/73 CPU with 2mb memory.
Sorry, which exact quad-height CPU card?
{As someone else has previously pointed out, the /73 and the /83 are basially
the same machine (roughly the same CPU board - KDJ11-B, perhaps with different
clock crystals), just with different memories - QBUS in the /73, PMI in the
/83. The /84 is an /83 with i) a different backplane and ii) a KTJ11-B UNIBUS
adapter.}
> On the positive side it's chock full of 256k chips, which I could pull
> off and put on the EA board to bring it up to 2mb memory. I have air
> heat tools and a pre-heater so getting the chips off should be pretty
> basic.
I would advise against that. 256K chips are readily available on eBait, and
for not much money. Pulling them may damage them, and may well also do some
damage to the memory card, in addition to making it useless.
> Getting them on the new board though could be a pain since all the
> holes are soldered over....
A vacuum desoldering station will easily open them. Used Hakkos can be found
on eBait for not too much money.
Noel
