Date   : Thu, 20 Jun 1985 21:46:22 CDT
From   : mknox <mknox@UT-NGP.ARPA>
Subject: Reply to: cpm 2.2 maximum disk storage space (?)

Your book is WRONG!  The maximum storage capacity of a single "logical"
unit is 8 megabytes.  This is inherent in the way the disk space is 
allocated by the BDOS.

However, not to worry.  You will find it not only possible, but indeed
very desirable to use your 10 megabyte drive as multiple LOGICAL CP/M
drives.  These can be split any way you like (i.e. 8 meg -- 2 meg; 4
meg -- 4 meg, whatever).  The secret is in the track offset parameter
in the disp parameter block (DPB).  Example:  I have one system which 
ahhas a 10 meg hard disk split as 1 meg -- 6 meg -- 2.5 meg -- 512 k

Just set up as many DPH and DPB tables as you need for each logical
disk.  All will call the same driver, which will receive a REAL track
and sector number.  Be sure to correctly size each logical disk in
the DPB, and specify the correct TRACK OFFSET to get to the first
track for the start of that LOGICAL drive.