Re: In search of bad 4164, 41256 DRAM

> I did a quick test with a 41256 just now and was happy I could 
> read/write all bits successfully. Then I realized I don’t have any 
> known bad 4164/41256 type DRAM chips on hand. So, if you happen to have 
> a few bad DRAM chips on hand and you’re in the USA I would gladly take 
> them off your hands.

I was going to suggest that, for testing purposes, you could extend the 
refresh interval far beyond specification.  That would cause even a good 
RAM to fail, and, all being well, the failure would be detected and 
you'd know your test regimen is effective.

Oops, but wait a sec...  This raises a more general question.  I hope 
your test regimen doesn't do its test reads too soon, because reading a 
cell also causes that cell to be refreshed.  IOW, the test isn't fully 
comprehensive unless you write to a cell, leave it alone for one refresh 
interval, *then* do a read to verify its contents.

Sorry if I'm stating the obvious; I'm just thinking out loud here!  Have 
fun, and thanks for sharing your project with us.

cheers,
Jeff