Date   : Sat, 17 Feb 1990 01:51:26 GMT
From   : xanth!rlb@mcnc.org (Robert L. Bailey)
Subject: Kaypro DSDD 5.25" floppy parameters

In article <1647@mipos3.intel.com> dbraun@cadev5.UUCP (Doug Braun ~) writes:
>In article <2756@lll-lcc.UUCP> rzh@lll-lcc.UUCP (Roger Hanscom) writes:
>>
>>Does anybody have the vital statistics on Kaypro 5.25" DSDD
>>floppies??  Things like sectors/trk, BSH, etc.  I believe they
>>should be about 390K with 10, 512b sectors/track.  I'm trying
>>to write a BIOS that will use the Kaypro format.  What is the
>>interleave for this format??
>>
>
>How is it that this format has 10 sectors per track, while IBM PCs
>have only 9 (and the old ones could only get 8 in)?
>
>I recently got a 5.25" floppy controller for my CP/M computer
>(which normally uses 8" SSSD), but it can only read 8 and 9 sectors per
>track.  Does anyone know a resonably popular CP/M format that I could adopt,
>and thus interchange my 5" disks with somebody?
>

The reason that IBM did not use 10 sectors/track is probably that they
decided that it was pushing the capacity of the media too much.  IBM
is a very conservative bunch, don't ya know?  The IBM hardware is
perfectly capable of reading/writing 10 sectors/track.  I know.  I have
a non-standard formatting program on my PC that DOES use 10 SPT.  

Most likely, your hardware is capable of handling 10 SPT.  You just need
an appropriate formatting program and new disk parameter tables in your
BIOS.  I have an old Xerox 820-1 that originally 8" only.  I added
a 5 1/4".  Later, I got a new double density controller from Emerald
Microware.  This allowed me to add more drives and accomodate different
disk formats as well.  My configuration ended up as follows:

       1       8" SSSD
       1       5 1/4" SSDD
       1       5 1/4" DSDD
       1       5 1/4" DSQD (80 trk double density - but not like IBM 1.2M)

These drives along with a program called UNIFORM allowed me to read/write
just about any format that exists, including IBM 360K disks!  

My standard format that I used most of the time was the Kaypro 5 1/4" DSDD
390K.  This is probably about as close to a "universal" CP/M format as
you will find, because the Kaypro machines were very popular in their day.
I believe that they were the top seller in the CP/M arena.

In summary, if your controller is capable of reading/writing double density,
then some new disk parameters in your BIOS should enable you to handle
the Kaypro format.  Check your controller chip. If its a Western Digital
17xx or 27xx, it should work (except for the 1771 which is SD only).  The
NEC 765 and others in that family are also capable (most PCs use one of these).

Hope this helps.
Bob Bailey