Date   : Thu, 27 Oct 2005 22:18:08 +0100
From   : "A. J. Davis" <mail@...>
Subject: Formatting a disk beyond 80 tracks

Has anyone ever done any experiments with formatting a disk beyond 80 
tracks?  I first noticed you could get a few more out of a disk about 
ten years ago with a 5.25" drive on a Sinclair Spectrum (with +D interface).

The format command was built in, but you were able to modify the DOS 
(ironically it had to be loaded in on disk first!) to the number of 
drives, whether they were single or double sided and the number of 
tracks. (it was a 10 sectors per track, 40 or 80 tracks per disk 
arrangement).

While 3.5" disks would usually only format to 81 tracks I found I could 
get upto 85 on the 5.25" disks.

This gave birth to some pretty good copy protection techniques where a 
hidden piece of code would search for a verification code on the hidden 
track and if it wasn't present would format the disk.

I was playing around with J.G. Hartson's disk format program - 
http://www.mdfs.net/Software/BBC/FormDFS.txt - and got some interesting 
results testing it on Beebem. I've not had the time to try it on my twin 
drives on the Master yet.