Odd MSV11-J bug (Was: MSV11-J engineering info)

Noel Chiappa jnc at mercury.lcs.mit.edu
Fri Jul 6 09:52:54 CDT 2018

    > I first have to tweak my 'scope loop program, to turn on memory mapping

So while doing that I just discovered what I _think_ (maybe I'm just not being
smart enough to see that it's somehow 'doing the right thing') is the wierdest
hardware bug I've ever seen.

Plug in an MSV11-J, disable ECC (store an '04' into the CSR), and then store
'0172344' into any location. Now read it back!

And it's not a bad RAM chip, which turning off the ECC is letting show
through, because I tried several boards, and they all do the exact same
thing. So either they've all got the same bad chip, or... :-)

I found this when my modified 'scope loop program (above) blew out, but none
of the other values used in that seemed to have a problem; but of course the
program didn't include all 2^16 patterns. I suppose I should whip up a small
program to try other values, and see if anything else does this...


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