19 Oct
2006
19 Oct
'06
1:18 p.m.
Jay you mention below 'The memory address test program fails though.'
Which memory address test program are you referring to? The M9312?
The M9312 11/34 console emulator has a simple memory diagnostic
that scans the low 28KW, writes the address of each word to the word,
and then rescans, negating each word value in memory. It then adds the
address to the negated word, and halts if the result is not zero.
Successful test execution results in all of memory being cleared.
Normally this test will only be run when you try and boot from some
device in your system.
See the console listing at: http://www.AK6DN.com/PDP-11/M9312/ under
the 'M9312 11/04,34 Diagnostic Console' listing.
If you have the capability to program an M9312 boot PROM I generated
an image for a pseudo-device 'ZZ' that does nothing but run all the
internal M9312 diagnostics forever (processor and memory). I've found
it very useful in situations like this.
joe heck wrote:
Well, I don't have the listing in front of me, but
perhaps there are
multiple passes through the memory test. Maybe it wrote out all the
inverted numbers fine on the first pass, then when it tried to write
the real numbers it failed (or vice versa). That way it will test all
the bits, although not adjacent bit stickiness. So, maybe try to
write the inverted number to 420?
Just my quick thoughts.
Joe Heck
Jay West wrote:
I just brought up my /34a and apparently it's
sick. It has one
DD11-PK. Configuration is as follows:
1 - M8266 (A-F)
2 - M8265 (A-F)
3 - M9312 (A-B), M7859 (C-F)
4 - M7891 (A-F)
5 - Grant (D)
6 - Grant (D)
7 - Grant (D)
8 - Grant (D)
9 - M9302 (A-B), Grant (D)
What works:
Storing & retreiving various patterns from ram via the front panel
works fine in all cases.
Looping on CLR PC loops as expected
Looping on BR . loops as expected
Trap catcher works (first pass halts at 1030 filling ram, then a BR .
loops as expected).
The memory address test program fails though. It halts at 246
indicating a memory addressing error. R1 points to 422. Examining
memory via the front panel shows the following:
420 420
422 177355
424 177353
426 177351
430 177347
So it looks to me like it is able to store 420 in 420, but nothing
after that. I would normally think there is a problem with the memory
board (M7891). However, I have replaced that board with 2 others, and
all 3 boards fail at the same address AND with the same values. I
find that likely to rule out the memory board as really being bad. In
addition, I can deposit and examine values to locations 420 through
430 via the front panel just fine. It's my understanding that the
KY11-LB puts data in memory via the unibus, so I would think this
makes it somewhat unlikely to be a backplane issue. Is it a strong
likelyhood that the problem is the cpu set itself then, as that's
what would be writing the values to memory during the address test?
And as I type this, I just noticed something interesting. The numbers
stored in ram at 422 through 430 are the right numbers, just inverted
logic. More specifically if you invert all the bits in 177355 you get
422, if you invert all the bits in 177353 you get 424, inverting
177351 gives 426 (all the latter values being what I'd expect). I'm
guessing there's a dead inverter on the cpu set somewhere perhaps?
But if that's the case, why does 420 get set to 420 correctly??
Any advice is most appreciated :)
Jay West