Re: Commodore 15 Second disk format routine disassembled

From: Julian Perry <jp_at_digitaltapestries.com>
Date: Sat, 11 Apr 2026 22:54:58 +1000
Message-ID: <1568390796.20260411225458_at_digitaltapestries.com>
Looking at the routines back in the day.
The Commodore routines were more a "measure the drive speed every track", then lay out the inter-sector gaps accordingly" routine. Very methodical, but hilariously inefficient. Also, considering that the bitrate was already hardcoded for each zone, totally redundant. 
The "fast'hack'em" routine just took a fixed zone specific routine, and laid out the tracks as designated, at the bitrate, errors-be-damned. 
I have not looked at the code, but I'msure Mike Henry has many interesting tales to tell - tales I'd love to hear.
 
 
 
> You could be interested in this:

> https://x.com/commodoreihs/status/2040555413326672219

> """
> It took over a minute and a half to format a new disk using the native Commodore 64 / 1541 disk drive commands. Mike J. Henry of Starpoint Software and Basement Boys Software (Fast Hack-'em) fame wrote a 15 second format routine, which was apparently at some point modified by Alf Maier. I don't know exactly what Alf modified, but I think this was widely distributed on QuantumLink in the mid-to-late 80s.
> You can download the program from Bo Zimmerman's site here:
> https://zimmers.net/anonftp/pub/cbm/c64/diskutil/routines/Format%2015%20seconds.prg
> I disassembled the code and uploaded the result to GitHub:
> https://github.com/commodoreihs/15_second_format/tree/main
> Does anyone know the precise history of 15 second format?
> """

> https://github.com/commodoreihs/15_second_format/tree/main

> https://zimmers.net/anonftp/pub/cbm/c64/diskutil/routines/Format%2015%20seconds.prg



-- 
Best regards,
 Julian                            mailto:jp_at_digitaltapestries.com
Received on 2026-04-11 15:00:02

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