Apparently they initially intended for it to have a fast parallel connection which would have meant a huge gain in speed, but they ended up with a serial bus on

Apparently they initially intended for it to have a fast parallel connection which would have meant a huge gain in speed, but they ended up with a serial bus on the C64 to be compatible with VIC-20 disk drives. This was supposed to be offset by hardware that could maintain a high serial speed, but the design ended up half broken, which they had to amend with the slow software routines before release. It sucks, but it's nice that the computer could patch the disk drive at run-time and have it run some more sophisticated software for a speed boost. For example, the Action Replay 6 comes with a "fast loader" that performs some 18 times better than the kernal loader and stock 1541 firmware on normal CBM formatted disks. Still not as quick as Woz' Disk II...