Star Wars / ESB reset problem

Tracked down a weird problem over the weekend. I had a Star Wars boardset
that just would NOT accept the ESB kit-- I had written it off as a fluke,
when another guy had the same problem. Not good. I had him send me his
problem boardset and I set out to figure out what the problem was.

To make a long story short, for boards that have a weird "reset a few
seconds after the gameplay starts" problem, the solution appears to be
replacing the 74LS244's on the address bus.

It's some sort of speed or bus loading issue (which kind-of explains why
swapping EPROMs out sometimes fixed it in some cases). I'm more inclined
to go with the bus-drive scenario, since replacing things with *faster*
parts doesn't always help. Replacing the '244s fixed it two out of two
times though.

-Clay

(This was a really screwy problem-- the boards would work with Star Wars
EPROMs just fine. Adding the ESB daughtercard but keeping the rest of the
EPROMs as Star Wars worked just fine. Swapping out even just one or two of
the Star Wars EPROMs with 27C256's (programmed with the same code) would
result in the "reset problem". Weird. Changing brands/speeds of EPROMs
didn't help. Changing out the '244s on the bus fixed it...)

Clayton N. Cowgill Engineering Manager
_______________________________________________________________________
/\ Diamond Multimedia Systems, Inc. clay@supra.com
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Received on Mon Dec 1 10:37:07 1997