Re: Commodore 15 Second disk format routine disassembled

From: Francesco Messineo <*francesco.messineo_at_gmail.com*> Date: Fri, 19 Jun 2026 09:34:14 +0200 Message-ID: <CAESs-_y4xsJTq_65Q-gNa88pDmb7oothUMhhQsDwaj8V7BQ8eA_at_mail.gmail.com> · francesco.messineo_at_gmail.com

On Fri, Jun 19, 2026 at 12:37 AM Maciej Witkowiak <ytm_at_elysium.pl> wrote:

> In its extended format disk the disk will have tracks 35-41 formatted and it reports 840(!) free blocks.
>
> It not only formats the inner tracks, but, if I got the disassembly right, the whole disk is formatted with the same density as tracks 1-17, with 21 sectors on each track.
> I'm not able to reproduce this in VICE or YaPe. I don't have a real 1551 to check how reliable this is either, but indeed it works on emulated Pi1551.

and how does it configure the clock divider to allow 21 sectors on the
smaller tracks?

IZ8DWF