WP34s&Co. - an internal flashdisk

[pito]

I worked with the above Cypress' fram and pic33. With 12MHz SPI clock I did random access r/w to a byte in 7us, to a larger block (ie. 64bytes) in ~1usec/byte.
I do not know what would does mean for wp34s, but with $5 nonvolatile 256kB sram your possibilities are virtually unlimited, moreover, the speed is not too important with pocket calculators, I think..