MSV11-J engineering info
jnc at mercury.lcs.mit.edu
Wed Jul 4 15:56:19 CDT 2018
> I'm going to need this info real soon ... so I'll probably start on
> this later today if nobody has the info.
> write a two-instruction loop .. which writes a word with only a single
> '1' bit, hook up a 'scope ... to a DRAM input, and walk the bit through
> ... just disable ECC, and write all 0's to all the ECC bits
> I think that ... it'll go reasonably quickly, actually; the more bits
> I ID, the fewer values I'll have to try on each succeding DRAM chip.
That was pretty easy; thanks for knocking my brain into gear! :-) The first
couple of bits I had to fish around, but pretty quickly it became apparent
there was a system, and for the rest it was just 'confirm that this chip does
indeed hold that bit'.
I now have the chip<->bit table for the even words, and most of the ECC bits
for them (there are two that have resistor headers next to them, so I can't
easily get a DIP clip on them to see which is which), but I'm getting bored,
I'll do the odd ones tomorrow.
Probably they'll be very similar (the array looks like a mirror image of the
one for the evens). Also, I was using a 1MB card, so I only had the low bank
to worry about; so then I'll have to do the high bank - again, probably pretty
easy, from here.
The blasted card doesn't have the usual DEC Exx chip numbers, though! I had
to make up my own for it...
> I'll add the info to the MSV11-J page on the CHWiki, once I have it.
Alas, it's down at the moment (the server is actually up, but its DNS entry
has gone away again), but once it's back, I'll get them right up.
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