14 May
2016
14 May
'16
11:23 p.m.
On Sat, May 14, 2016 23:41, Noel Chiappa wrote:
Could that be done on later models? (i.e. 11/24 and up?)
Yes, a typo, it is a M7891.
Ah, that reminds me, I have an original DEC Unibus analyzer, which is
one of those small suitcase sized boxes and has a display for all
bus signals. Stupid that I didn't think about that.
Ah, well it was not set for EBU mode, but ISTR that there is a jumper
which selects for +12 or +15 volt.
Yes, both +5 and +15 is used and measure ok on the backplane.
From Ed
Groenenberg
- insert both CPU cards, KY11-LB card &
bootstrap card, 5 full grant
cards, DL11-W and bus terminator card.
...
- cntrl + boot shows register dump at printer.
...
All looks ok
I'm surprised the bootstrap ran OK with no memory at all in the machine. I
vaguely STR that I had a machine that would not work like that, but maybe
I'm
wrong. (DEC bootstaps tend to do things like set the NXM vector, in low
memory, so they can size memory; and when it gets the NXM (since there is
no
memory) from trying to touch the NXM vector, and tries to push the old PS
and
PC to service _that_, and gets _another_ NXM, that 'double bus fault'
often
causes many -11 processors to do a cheap suit) power down machine, add memory (M7981, 128KW)
What's an M7981? Did you mean an M7891 MS11-L? - power up machine -> run light is on, does
not get cleared by
cntrl + halt.
This is where a UA11 would really help. I had similar issues with an
-11/04,
and the UA11 was a huge help in figuring out what's going on. One glance
and
you can see if a bus line is wedged, or something. - power down & replace memory with grand card
-> run light is off.
Well, that's good sign - the memory card didn't fry anything, at least...
- tried a 2nd memory card (M8722, 128KW)
Ooops. The MS11-M needs +/-12V, which is _not_ standard in most
machines/backplanes). The EUB in the 11/24 and 11/44 (which this card is
intended for) does have it. The really bad part is that those same pins
usually carry +/-15V in most MUD backplanes. So hopefully you didn't fry
it.
It does have standard UNIBUS as well as EUB, but there's a jumper, IIRC. So what could
be the problem here? The bus works without the memory
Two possibilities off the top of my head. i) The first memory card is bad
(or
configured incorrectly), or.. ii) The M7891 uses +/-15V as well as +5V? So
maybe one of the other voltages is not so good? But you said the console
worked, and I think that uses other voltages (at least, in EIA mode - not
sure about 20mA, I never touch the stuff).
Noel
Ed
--
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