We make an embedded system using a 386EX that works great with Cypress 55 ns static ram. Cypress now only makes this ram in a 45 ns version (CY62157), but our system won't work with these. Apparently there is some sort of deterministic write to ram problem that is unaffected by wait states. How can faster ram ever cause a problem? Anyone ever seen a problem caused by using faster ram?
Further investigation indicates the problem is actually a read from ram problem, not a write to ram problem. The 45 ns part has a smaller die but the same capacitance spec. I'd assume the capacitance is actually less; could this cause it to be more sensitive to bus glitches?
we recently encountered similar problems with this combination.
Please check the Cypress website for AN66311. This describes the cause,
at least in our case.