4 Jul
2018
4 Jul
'18
1:56 p.m.
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.
Noel