I'm considering a project here where I'll need a reasonable amount of storage in an otherwise "small" system. The spec hasn't been firmed up yet but I imagine we're looking at a 16 bitter CPU, probably a PIC18 or an MSP430. "Reasonable" storage in this context means no more than 100MB. Volatility isn't a problem but the rewrite cycles are such I'd be wary of flash storage, so I'm finding myself drawn towards a RAM disk - i.e. not directly addressable memory but something that can be accessed after the requisite port set up.
Looking at memories the pricing of commodity DDR2/3 DIMMs are certainly very attractive but I'm a little hesitant over the interfacing requirements - I'm used to operating at a few tens of MHz, no more than double-sided PCBs and I know next to nothing of transmission lines. Can these memories be underclocked to that extent and still behave nicely, or does anyone have other insights?