Hi All,
I've been testing an M7869 recently and noticed that my 11/34 would give a
BUS ERR whenever it was halted or if I tried to read from the switch
register, so I used the "wholly scientific" fingerpoken troubleshooting
method and noticed the ROM at U33 (P/N 23345A9) was piping hot.
Does anyone have a dump of this ROM that I could use?
Regards,
-Tom
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Hi all,
I accidentally dropped something on a Miniscribe 6053 44MB HD and cracked the board; looks pretty dense and tricky to repair so I'm hoping that there's a kind soul out there somewhere who happens to have a 6053 doorstop and can spare the circuit board for a good cause?
Removing the board shouldn't impair the door-stopping capability in any way...
Mike (in Toronto)
> From: Glen Slick
> You should also hang out at vcfed forum in addition to hanging out here.
I barely have time to keep up with the things I'm already into (actually,
strike that - I _don't_ have time to keep up already :-)! So I'm going to
have to pass.
Interesting about the FP11 stuff, though. I wonder, however, if those 11/20
mentions are more aspirational, rather than something that was actually done,
and later dropped? I say this knowing a modest amount about how the KA11 CPU
in the 11/20 works, and a bit about how the FP11-B interfaces to the host CPU.
For one thing, it would take some modifications to the KA11 to recognize
floating point instructions, so that it can wake up the FP11-B to handle
them. But that turns out to be the easy part; it would take further mods to
the KA11 because the FP11-B expects the host CPU to do data fetches, etc on
its behalf. (See Figure 2-3 in the FP11-B MainManual.) This latter function
can't be off-loaded onto a separate interface unit, as it needs access to
register contents held in the CPU.
I don't have the time to look into this further, but if someone is interested
they'd need to study the FP11<->CPU interface, and in particular look at how
the KB11 supports memory operations requested by the FP11-B - I wouldn't be
suprised if there's some microcode in the KB11 to support those memory
operations.
Noel
Putting this out there for those hopefully in the know.
I have been acquiring date-correct ICs and parts for my Mark-8 project,
which is years down the line. I'm planning to build it on very carefully
replicated clone boards, based off my originals. For my purposes, I'm
trying to keep ICs early 1975 or earlier.
Most Mark-8s that I've seen have P1101a plastic encapsulated RAMs. Most are
Intel brand, but I've seen some that I think might be National or
something.. they just say P1101A on top.
The only source other than ebay that I have are those big chip vendors like
Summit. And the problem with them is they aren't always precise about date
codes. The P1101A, because they were produced for years, have a wide range
of codes and the places I prospected them from couldn't guarantee 75 or
prior.
To my surprise, I found a few places had C1101A. They are white ceramic,
gold legs. They have a 'batch code' of F1268. I got 16 of them for $14
each. I was going to get 32, but Summit also surprised me with 5 1973
vintage Signetics n8263s @ $25 each. I hadn't been able to find any
pre-1980 so I snatched those.. but that put me beyond a budget where I could
buy 32. I figured I'd buy 16 chips for now and then buy another 16 the next
month.
Now of course, the chip houses have turned tables on me. They want $48 per
chip instead of $14 like last time. And checking around, that seems to be
uniform. Now, I'm not averse to paying that, though it will sting. But I
want to make sure my assumptions are correct.. that these white vintage ICs
are in fact pre-76. Can anyone confirm that? The info out there is a
little vague.
And would it be totally out of place for C1101as to be on a Mark-8? Could a
hobbyist have had a source for them, beyond having some lying around?
> From: Pete Lancashire
> Do you or someone have a list of all the Unibus bus chips ?
I have seen the following bus interface chips used on DEC UNIBUS boards:
Drivers:
8881 - Sprague, Signetics - Quad NAND
Receivers:
380 - Signetics - Quad NOR
314 - Signetics - 7-input NOR
8815 - Signetics - 4-input NOR
8837 - National Semi - Hex receiver (aka Signetics N8T37)
8640 - National Semi - Quad NOR
Transceivers:
8641 - National Semi - Quad transceiver
The actal complete part number can vary depending on the manufacturer; e.g.
the 8641's are usually DS8641N, from NatSemi, and the 380's are usually
SP380A's or SP380N's. Where the basic number is not included (as with the
8T37 for the 8837) I have given it.
The following chips have been used by DEC to interface to the QBUS, and
I have seen many of the above chips (e.g. 8641's) used there too, so I
think chips seen on one bus could be used on the other:
Drivers:
7439 - Various - Quad NAND
Transceivers:
2908 - AMD - Quad latching transceiver with tri-state output
I _believe_ the following chips are also usable as UNIBUS/QBUS interface
chips, but I'm not sure if I've seen one used there:
Transceivers:
8836 - National Semi - Quad NOR
8838 - National Semi - Quad transceiver (aka Signetics N8T38)
Quite a zoo!
Noel
> From: Mark Moulding
> I did a bulk buy of some 1960's era miniature vacuum tubes (500 pcs)
> for around 50 cents each; the next time I looked, the price from all
> vendors who had them had jumped to around $3
There is another possibility (one which I think I saw happening when Guy and
I were buying DS8641's, which we previously discussed here), which is that if
multiple vendors have stock, an initial order might buy up the ones with the
cheapest price, and a second order will wind up being met from a different
dealer's stock, one with a higher price.
Noel
