@elmasta
If memory serves correctly it comes down to speed / refresh and access time.
Compact flash although fast is still woe-fully slow compared to PCMCIA - SRAM which functions from 250ns to 100ns, where CF is measured in milliseconds (for both reading and writing)
the 4MB SRAM i have operates at 150ns read / write and refresh
although i believe it would be possible to configure the CF card as memory (after a lot of effort), it would be that slow it would be unusable
.
because A600 ram and cpu expansions are so rare I decided to hit up Aminet and see if i could redevelop some of the hardware upgrades for the A600 since they are pin-compatible on the CPU, i have some success but only in the schematic and pcb design, i have yet to build one
but when i shake this god damn flu and finish of some Svideo units then whoot thats my next thing
in fact I hope to be able to put a small card with 4MB of ram AND an EC020@20mhz I hope to be able to keep it under £20 too