Re: testing RAM chips

>And even that is not a guarantee. I pulled some from a problem Gorf board
>and stuck them in a Galaga. Passed self test every time but every 5 or 10
>minutes the game would do something "extra special" or crash. Should I
>throw these RAMs away? I hate to keep them but they're not cheap anymore
>so I have been hesitant to throw them away too. Maybe they'll work at a
>slower bus speed? I know, I know. Just begging for more frustration!

Definately don't read my last message as using the built-in RAM test on a
game as being the "final" answer! The built-in RAM test is almost certainly
better that trying to spot a bad RAM on a working databus with a logic probe
or o'scope though. Also, running in system is probably better than using a
stand-alone device tester.

A "professional" RAM tester will usually do a variety of tests (walking
bits, patterns, random read/write, etc.) at several voltage levels and ever
increasing speed over a long time. Also with varying temperatures too...
Fancy ones will know the layout of the die in question from certain
manufacturers and beat on known weak-spots ("Micron's row drivers for block
zero come off the same supply as the column driver for block three, so we'll
write to block three and read from block zero and look for flipped bit
#4's...").

If you've got a somewhat flakey RAM chip... I keep 'em cause they're handy
for testing RAM test routines, but in a game-- replace it. It'll save you
time down the road.

-Clay
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Received on Tue Apr 25 21:17:19 2000