Re: Informations about JiffyDOS

From: Nicolas Welte (
Date: 2001-03-15 11:07:17

"Carlsson, Anders" wrote:
> Marko Mäkelä wrote:
> > JiffyDOS doesn't make use of the fast serial bus (burst mode) on
> > the C64, because it doesn't require any hardware modifications.
> Ah, ok. I thought hardware modifications and the burst mode were
> involved. How about Dolphin DOS, Professional DOS and all the other?
> Does any of these use burst mode, and possibly can't be used at the
> same speed with the VIC?

Those speeders are parallel speeders that transfer one byte at a time via an
extra cable that connects the 1541 VIA directly to the user port of the
C64/128. Normally no burst mode is involved. But if you use Dolphin DOS in
C128 mode, and switch off the parallel cable with the XP- command (or just
unplug it), you will not notice much of a slowdown, because then Dolphin will
fall back to serial burst transfers which are almost as fast as a parallel
transfer. Much of the speedup of those speeders is due to optimized GCR
decoding (with large lookup-tables) and the ability to store a whole disk
track in their extended drive RAM. How fast this can be transferred into the
computer doesn't matter too much. Remember that Speeddos also had the same
parallel cable, but still was not faster than Jiffy DOS.

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