Re: Commodore 15 Second disk format routine disassembled

From: Peter Rittwage <*peter_at_rittwage.com*> Date: Thu, 16 Apr 2026 16:52:22 -0400 Message-ID: <CAJxOZi1+CHYiaL=L8-c9RhsKs4VsuijOzPx-jfpbOh5L63wvwA_at_mail.gmail.com> · peter_at_rittwage.com

The track data is written "wider" than an 80-track drive, though, so is it
actually incorrect?

On Thu, Apr 16, 2026 at 4:34 PM <silverdr_at_srebrnysen.com> wrote:

>
>
> > On 16 Apr 2026, at 14:12, Jesus Cea <jcea_at_jcea.es> wrote:
> >
> > On 11/4/26 3:16, Jesus Cea wrote:
> >> You could be interested in this:
> >> https://x.com/commodoreihs/status/2040555413326672219
> >
> > Now a Youtube video:
> >
> > Technical Deep Dive: 15 second format routine for the Commodore 64 and
> 1541
> > https://www.youtube.com/watch?v=74EKB7gdDv4
>
> Minor inaccuracy inherited from the previous video is the visualisation of
> the tracks on disk layout. 1541 is an 80 track drive but with the head it
> is equipped with and double-stepping it is made to be effectively 40 track
> drive, not 35 track one. CBM DOS simply does not use the innermost five
> tracks, presumably as a reliability safety margin. This means the
> visualisation, which shows the tracks spread evenly across the surface with
> no unused portion is not really correct.
>
> --
> SD!
>

-- 
-
Peter Rittwage