Re: upgrading CBM-3040?

From: Ethan Dicks <*ethan.dicks_at_gmail.com*> Date: Wed, 15 Nov 2017 15:46:32 -0500 Message-ID: <CAALmimkdSmA2spt-a=L4S4G+cw3u_VGF0jy7gVfPR3i7jNw8tQ@mail.gmail.com> · ethan.dicks_at_gmail.com

On Wed, Nov 15, 2017 at 3:33 PM,  <silverdr@wfmh.org.pl> wrote:
>
> Isn't what's written in that book about the differences between 1541 and (AFAIR) 2040, not 2040 and 4040? And none of the the two other are compatible with 1541?

The DOS 1.0 format (with the extra block in one zone) is the "2040"
format.  DOS 2.0 and DOS 2.6 use the same on-disk format in terms of
sectors-per-track and are fully compatible.  What might be different
is *I think* when you format a disk on DOS 2.0 (4040), the data bytes
are $00 and on DOS 2.6 (1541) the data bytes are $4b/$01... because of
an INX bug in DOS 2.6 (as documented in "Inside Commodore DOS", IIRC)

The primary problem is taking a DOS 1.0-formatted disk and wanting to
write to that on a newer drive.

-ethan

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