> Even 4MB would take you hours to load from floppies with a 6502.

Depends on your clock. Also, you could use some dedicated hardware, like a DMA controller e.g. 8257, or 8237. From 8257's datasheet:

    Speed

    The 8257 uses four clock cycles to transfer byte of
    data. No cycles are lost in the master to master transfer
    maximizing bus efficiency. 2MHz clock input will
    allow the 8257 to transfer at rate of 500K bytes/second.

and I recall 8237 could do even better, if wired and programmed properly.