> On Jan 20, 2019, at 3:56 PM, Fritz Mueller via cctalk <cctalk@classiccmp.org>
> wrote:
>
> ...
> I'm technically curious, now, about the failure modes of these sorts of
> DRAMS. I guess in addition to stuck bits, there are also potential decode
> fails (show up on address test, but not ones/zeros) and some errors that have
> history-dependence, perhaps internal latches (show up on random data test,
> but not address or ones/zeros.) I'd guess also there might be potential for
> crosstalk, noise, and "fading bit" type issues as well? Will have to see
> after I make the next round of repairs if there are still additional problems
> that the MAINDEC flags that my simplistic diag isn't shaking out.
There are tests for crosstalk and decode problems, they may be marked as core
memory tests but they might work anyway. There is the "no duplicate address
test" which verifies that each word is accessed by exactly one address value.
That would catch decode issues -- for example, a stuck address bit or a stuck
decoder would be caught quickly.
Not quite crosstalk, but there is the famous "core heating test" which hammers
on a specific set of addresses which are near each other in the core mat, to
see if the heat generated by those rapid accesses in a small physical area
cause trouble.
paul
