Talk:Epyx Fast Load

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How did they do it?[edit]

Does anyone know how the FastLoad systems worked? What, technically, did they do?

Fast loaders used a faster (custom) serial protocol. This was possible because you could send code to the disk drive and thereby modify its operation. Mirror Vax 05:16, 27 July 2005 (UTC)

Thank you! The Commodore_1541 page seems to bear this out:

The 1541 used a bit-serial version of the IEEE-488 (GPIB) parallel protocol. The simple protocol that the built-in DOS used supported only about 300 bytes/s. Some third-party speed-ups, however, could transfer about 4 kilobytes per second over the interface, and some "fast loaders" managed up to 10 kbytes/s.

Indeed, the serial bus timing diagrams on p 364 of the Commodore 64 Programmers Reference suggest that there is a LOT of handshaking that is done between every 8 bits. The computer has to acknowledge receipt of every byte. I suspect one could chain a number of bytes together into a larger block, and the chips will still be able to maintain timing. This seems like it would only be a marginal speed increase, though -- maybe 50%. I'm still curious what else they might be doing.

The Commodore 1541 user's guide suggests two other books -- one of which I may actually own. If I recover it from storage, I will see if it has an answer.

You need to understand that the protocol is done completely in software. This is actually the root of the problem - even though the 64 had the hardware for a serial port (in the CIA chips), it was not used because of a desire to be compatible with VIC-20 peripherals. Mirror Vax 01:05, 28 July 2005 (UTC)
But how many C64 users actually used VIC-20 peripherals? :-) Frecklefoot | Talk 17:06, July 28, 2005 (UTC)
Well, the final twist is that the 64 wasn't compatible anyway. The Commodore 1540 wouldn't work, at least not without blanking the screen, due to the CPU being halted every 8th line (on the VIC-20 the CPU always ran at full speed). Mirror Vax 17:52, 28 July 2005 (UTC)
Indeed, the UI- command "speeds up the 1541 when used with the Vic-20 only." according to the 1541 user's guide. mdwyer (should really sign up for WikiPedia...) -- 03:23, 29 July 2005 (UTC)