I recently encountered a curious ideosyncracy concerning Hitachi HN27C64-2
Eproms. I found that my EPROM programmer was unable to accurately read one.
Each time I tried to verify that I'd dumped it to my buffer, ther were about 12
bad bytes (different ones mostly each time) reported.
Finally I decided to treat the EPROM as if it were a dynamic ROM… the
sort that has to have its enable lines strobed each time you read a byte out of
it. (My EPROM programmer is a crude one that only holds the enable lines high
during reads… it does NOT strobe them).
Well… I hooked the sucker up to my system bus on my CoCo, and whaddya
know… it read reliably and consistently. (My CoCo DOES strobe the enable
lines when it reads the EPROM. )
I've previously used 2716's, 2732's, 2532's, 2764's, 2564's, 27128's, and
27256's with my programmer in both CMOS and "A" varients, from Fujitsu, Intel,
SEEQ, Hitachi, NEC, AMD and others. This is the first time I ever encountered
what appears to be a "dynamic EPROM".
I just wanted to share with you and any other tech types present here this
curious experience. I invite comments.
—Marty