Re: Commodore 15 Second disk format routine disassembled

From: Peter Rittwage <*peter_at_rittwage.com*> Date: Fri, 19 Jun 2026 09:26:49 -0400 Message-ID: <CAJxOZi0L+KPZiHEqWPm1HcfacipFK74nX5gcSrGOceVTue2Y_A_at_mail.gmail.com> · peter_at_rittwage.com

FWIW, the 1551 had the exact same mechanisms (usually Mitsumi/Newtronics,
possibly some Alps) as the 1541's.

On Fri, Jun 19, 2026 at 9:25 AM Francesco Messineo <
francesco.messineo_at_gmail.com> wrote:

> On Fri, Jun 19, 2026 at 3:14 PM Maciej Witkowiak <ytm_at_elysium.pl> wrote:
> >
> > On Fri, Jun 19, 2026 at 2:16 PM Francesco Messineo <
> francesco.messineo_at_gmail.com> wrote:
> >>
> >> let me change slightly the question: how does the firmware pack 21
> >> sectors on the smaller tracks without running out of space?
> >
> >
> > It just never changes the speed zone setting
>
> yes yes, now I've engaged the brain and I get what it does. Of course
> it works but I suspect it won't be super reliable every time.
> Transitions per inch-wise it's well within the magnetic media
> possibilities, it would just need a better magnetic head but maybe
> 1551 mechanisms had a much better head than the shugart 400 drive that
> set the limits of the original 3040/1541 format.
>
> Thanks
> IZ8DWF
>
>

-- 
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Peter Rittwage