Date   : Tue, 29 Sep 2009 19:52:36 +0100
From   : dl.harper@... (David Harper)
Subject: M512 BeebEm 800k disc format

F. Haroon wrote:

> I didn't think that DOS had an 800K format, only the 640K: less than the 
> 1.2MB.

The Master 512 had a couple of non-standard disk formats. These were the 
640k (bootable) and 800k formats.

The 640k one is a hybrid with ADFS, and shares with it the pattern of 
sixteen 256-byte sectors per track. The 800k one has five 1024-byte sectors 
per track. (All MS disks have 512-byte sectors.)

For details of these see:
    http://www.cowsarenotpurple.co.uk/bbccomputer/master512/format.html

David Harper