Bummer time.... I turned on my VXT2000+ today and after about
5 minutes there was a "pop" and a small puff of smoke from
the power supply. No smell like you get from a selenium diode
or other semiconductor. Now, the fan tries to run but only
twitches and the led blinks slowly. No obvious blown part
visible. Does anyone have a service manual for the H7109-B
Power Supply? I would really like to fix this but I can't
see paying $150-$250 for a replacement. (Actually, if I had
that kind of money I would, but I don't!)
bill
> I'm trying to find a way to get my DEC Rainbow's monochrome output onto a
> newer monitor than my aging VR201 (especially since I zapped something in
> it and my diagnostic efforts to date haven't fixed it).
I can't remember the video output on the Rainbow, but I wanted to do
something similar to have one setup for the S-100 machines. After
looking on eBay (before I banned them from my use), I found a device
that basically had RCA audio/video inputs with a VGA output. It also had
the advantage of having an analog TV tuner built in so I could also use
things like the old video games that had the Channel 3/4 output.
The device is buried somewhere so I can't tell you the brand.
> From: Fritz Mueller
> The most efficient way I think would be to work up a simple LDA loader
> that would fit in a boot sector, and load a diagnostic from contiguous
> disk starting at the second sector. It would then be easy to blast down
> just the boot sector and a single desired diagnostic
Yup, an .LDA loader wouldn't be hard.
> The good news is that my enhanced diagnostics now detect failures in
> the same physical banks and with the same bits
Excellent! I imagine you're busy with a soldering iron at this moment? :-)
Once those are fixed, it will be interesting to see if the problems you saw
with the OS's go away.
It'd be easy to hack V6 to turn on parity error detection, if you'd like to.
> Will have to see after I make the next round of repairs if there are
> still additional problems that the MAINDEC flags that my simplistic diag
> isn't shaking out.
It will be interesting to hear those results...
> I've also been somewhat surprised by the level of repair needed on this
> memory board. So far, I've seen 6 failed 4116 out of an array of 144
> total, so about a 4% failure rate. Is this typical for vintage 4116
I don't know about 4116's, but I've seen a fairly high failure rate on _some_
cards with 256K DRAM's - on one board, a couple of chips totally dead, some
others with just _some_ bad bits. Other cards were totally fine. I suspect it
depends on the chip manufacturer.
> Might be just a fastbus thing?
Could be - I'm not too familiar with the Fastbu.
> It's also hinted in paragraph 7.7.7 of the older KB11-A maintenance
> manual .. This particular text is removed from the later KB11-A,D
> maintenance manual, and the description there seems to imply all reported
> parity conditions trap directly to 114.
Ah... Looking at the "pdp-11/45 processsor handbook", 1972 and 1973 editions,
there's an "Appendix E: Memory Parity" (of which I was previously unaware!),
referred to in "2.5.6 Memory Parity". (I haven't checked to see if later ones
have it.) It claims there are "16 memory status registers ... each one
associated with an 8K section of memory". (It doesn't say whether UNIBUS
memory, Fastbus, or both!)
One bit in each register claims to be 'Halt Enable': "[when] set, the machine
will execute a halt if a parity error occurs"; when clear, it traps to 4!
Even better, it claims to be able to control whether the memory uses odd or
even parity! (How, for UNIBUS memory, I don't know - there's no way to do
this over the UNIBUS. And the MM11-L and MM11-U manuals indicate they both
use odd parity, although there's a CSR bit to allow wriring 'wrong' - i.e.
even - parity.)
Very odd. Maybe this was deleted in the hardware (or they decided not to do
it), and someone forgot to follow through in the manual? I recently found
another reference to a /45 CPU feature I'd never heard of - forget what it
was, alas!
> surprisingly, neither one of my M8106 has either a jumper or the
> indicated pull-up at that location! .... The fact that W1 exists on the
> M8119 is interesting; maybe the situation is that the prints are for
> later revisions, and my actual M8106 are earlier?
Could be. I wonder if there's any way to get ahold of the ECO list for that
card?
Noel
Anyone in the UK want a handful of Sun SCSI cables. Six cables of various
lengths with various combinations of narrow, wide and ultrawide connectors
including the tiny SCSI connectors. 5 quid as a paypal friend will cover
postage.
Regards, Mark.
All,
I'm looking for hardcopy of:
* Intel MCS-80 System Design Kit User's Guide
* Intel MCS-8 Manual (8008)
* Intel PROMPT-48 Microcomputer User's Manual
I've got PDFs of these, but I like original dead tree format when I can
find it.
Thanks,
Jonathan
> From: Paul Koning
> It checks if the bits 007750 are active in the parity CSR, if so it
> takes that to be an address/ECC parity CSR.
That's odd; those are the 'error address' bits. Maybe there's an assumption
that the sweep of memory to size it will have caused a parity error from
garbage in DRAM at startup? (If so, I wonder if it would work on a machine
with all core? :-)
> It figures out the CSR to memory association by going through memory in
> 1 kW increments ... This should set bad parity, and it scans all the
> CSRs to see which one reports an error ... If no CSR has that set, it
> concludes the particular block is no-parity memory.
Oooh, pretty clever - good workaround for rhe undefined relationship between
CSR's and memory.
If I added parity support to V6, I'd be tempted to do it with a
hand-configured table - devices are all manually configured anyway in V6, so
I'd be continuing a theme... :-)
Noel
2nd seller indicates he is the first seller. Just selling on UK eBay. Don?t think you need different IDs to do that but what the hey. Whatever floats your boat.
Hi All --
Thought you folks might be interested -- I've been working on a Xerox
Star emulator at LCM+L on and off over the past year and I've finally
unleashed it upon the world.? It's called Darkstar, it's open source and
it runs all the Star software I'm aware of.? The Ethernet interface is
still mostly untested, however.
You can grab the emulator and its source code on our GitHub site
here:https://github.com/livingcomputermuseum/Darkstar.? Disk images are
available on Bitsavers as always.? Thanks to Al for providing a lot of
assistance on this project.
Please let me know if you have any questions or suggestions.
Thanks!
Josh
