memor cas question

is memory prettey much backwards compatible ??

if i buy cas 3 rated memory will it most likely be able to run cas 2 at way slower speeds ??
i want to but some pc 4500 (PC566) but would like to know if it would run cas 2 or 2.5 at about pc3700 (PC466) speeds ??
i know its kinda vague but is tighter timings all waya allowed when runnig slower than rated speeds ??

When you go up to non-standard ram speeds it's hard to make the call. I know the majourity of PC3200 spec'd at CAS 3 will do CAS 2.5 or lower at 166 and for sure it will do CAS 2 at PC2100 speeds.

I've seen a lot of PC4000 ram going really high in FSB but won't go lower than CAS 2.5 at speeds above PC3200. It's better to decide your RAM by the ICs on it than it's rating.

I doubt that it will do cas 2 at PC3700 speeds unless it is TCCD chips. BH-5/6 can do it as can some CH-5, but those are not made anymore.