Re: Custom floppy reading hardware interface

From: Michał Pleban <>
Date: Mon, 20 Jan 2014 15:34:55 +0100
Message-ID: <>

Anders Carlsson wrote:

> As long as the interface is only meant to read floppy disks, I suppose
> high density floppy drives are fine. You may even write to floppy disks,
> but if I understand correctly one should beware making changes on the
> disk using a 40 track mechanism later on.

>From what I remember, it's the other way around when writing disks - you
will have trouble when you write on 40 track drive, then on 80 track
drive. The reason I was being given is that in the 80 track drive, the
writing head was supposed to be narrower in order to write narrower
tracks. So when you format a disk on 40 track drive, this crates wider
tracks. Then when you write with a 80 track drive, you will overwrite
only a part of this wide track with your narrow head. So you will be
able to read this narrow track in another 80 track drive, because it
will only see the narrow part. But trying to read it back on 40 track
drive will result in an error, because its wider head will see some
parts of the wide track and some parts of the narrower track laying on it.

That brought me to another question I never found an answer to: why
can't you format a high density 5.25 floppy on a 1541? Only DD (and
probably QD) but not HD?


       Message was sent through the cbm-hackers mailing list
Received on 2014-01-20 15:00:03

Archive generated by hypermail 2.2.0.