27 Jul
2012
27 Jul
'12
9:08 a.m.
I'm curious if anyone has ever debugged an QBUS MSV11 board.
I have one which appears to have a bad memory location - a single bit
error. I assume this means there
is one bad dram chip. But I've never debugged a memory board like this
before.
Is it possible to figure out which chip is bad? (it seems obvious the
answer is yes, but how?)
I know the location - is there some reasonable way to map that back to
the chip?
I guess I could hunt and peck by grounding or pulling high the outputs
of different chips and
running the memory diag.
any thoughts?
-brad
27 Jul
27 Jul
9:45 a.m.
On 07/27/2012 12:08 PM, Brad Parker wrote:
I'm curious if anyone has ever debugged an QBUS
MSV11 board.
I have one which appears to have a bad memory location - a single bit
error. I assume this means there
is one bad dram chip. But I've never debugged a memory board like this
before.
Is it possible to figure out which chip is bad? (it seems obvious the
answer is yes, but how?)
I know the location - is there some reasonable way to map that back to
the chip?
I guess I could hunt and peck by grounding or pulling high the outputs
of different chips and
running the memory diag.
any thoughts?
Got the schematic? From the address you should be able to figure out
which row it's in, and narrow it down to the chip by which bit is bad.
I've fixed bunches of memory boards that way (admittedly no MSV11s that
I can recall), I don't see why that approach wouldn't work here, given
the schematics. You'll just have to trace through the address decoders
for the addresses and the data bus buffers for the bits if they're not
annotated on the schematic.
-Dave
--
Dave McGuire, AK4HZ
New Kensington, PA
2:18 p.m.
Which flavor of MSV11? I think the MSV11-D schematic is on bitsavers. Don't
think I saw any other versions there.
2:26 p.m.
In article <CAM2UOwLPUGsCPW9QwEnODNhXvhZqgJX6SUe1srcVe4kQT=jKEg at mail.gmail.com>,
Glen Slick <glen.slick at gmail.com> writes:
Which flavor of MSV11? I think the MSV11-D schematic
is on bitsavers. Don't
think I saw any other versions there.
MSV11-B Field Maintenance Print Set
<http://manx.classiccmp.org/details.php/1,6199>
--
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<http://tinyurl.com/d3d-pipeline>
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The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://legalizeadulthood.wordpress.com>
1:15 p.m.
I'm curious if anyone has ever debugged an QBUS MSV11 board.
I have one which appears to have a bad memory location - a single bit
error. I assume this means there
is one bad dram chip. But I've never debugged a memory board like this
before.
Is it possible to figure out which chip is bad? (it seems obvious the
answer is yes, but how?)
I'd look at the schematics. IIRC the MSV11 uses 16K*1 DRAM chips, so each
DRAM contains a particular bit of the word for 1/4 of the words on te board.
From the schematic, you can see which DRAMs (there will
be 4 of them)
handle the bit that's failing. Then you look at the address
decoding
circuitry to see which of those RAMs contains the failing location. And
change that chip.
-tony
4531
days inactive
4531
days old
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ard＠p850ug1.demon.co.uk -
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