Universal drive

From: Sam Ismail <dastar_at_ncal.verio.com>
Date: Fri Oct 2 13:20:53 1998

On Fri, 2 Oct 1998, Cameron Kaiser wrote:

> You could be just as tricky with Commodore peripherals because the Commodore
> drives had their own RAM, ROM and 6500-series CPU. Enterprising programmers
> created 40-track DOS for it instead of 35 (some 740-odd sectors free instead
> of 683) and Commodore fastloaders have long been based on this, usually using
> the CLK, SRQ or ATN line as a second DATA line on the serial bus and custom
> software on either end.

You could easily hack Apple DOS to 40 tracks, but the limitation was some
hardware (drives) couldn't seek that far. The Apple Unidisk (or 5.25"
drive as it was later generically called) was only capable of 39 tracks.
I can't remember what the original Disk ]['s could do. I remember being
able to get some drives up to 40 tracks.

> One of the most original uses for the Commodore disk drives, though, was
> nothing data transfer related. A math demo for the 64 used the 1541 as a
> co-processor for calculating the Mandelbrot set. Unfortunately, this didn't
> yield the speed increase one would think because of the slug-like speed of
> the Commodore IEC serial bus, but it was still significant, and a neat idea.
> I would think similar things have been done with Atari 8-bit drives.

This is indeed clever. Hans Franke was telling me about some guy in
Europe (Germany?) who hooked up a bunch of 1541's to a single C64 and then
parted out a Mandelbrot calculation to each to do extremely fast Fractals.

I think the coolest C64 disk drive program was the one that made the drive
play "Daisy" by recalibrating the drive head at different intervals; the
drive head would be hitting the stop at different frequencies and created
a violin like sound. I was fascinated with it. I attempted the same on
the Apple with a Unidisk drive, but the best I could achieve sounded
closer to a Tuba under water. Or a goose being choked.

Sam Alternate e-mail: dastar_at_siconic.com
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Received on Fri Oct 02 1998 - 13:20:53 BST

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