[sebhc] h17 and h8d disk images

Barry Watzman Watzman at neo.rr.com
Wed Sep 1 21:29:29 CDT 2004

Which IMSAI disk system?  The old dual Calcomp, with the IFM/FIB, or the
later one with the DIO/PDS?

-----Original Message-----
From: sebhc at sebhc.org [mailto:sebhc at sebhc.org] On Behalf Of Dwight K. Elvey
Sent: Wednesday, September 01, 2004 10:21 PM
To: sebhc at sebhc.org
Subject: Re: [sebhc] h17 and h8d disk images

>From: "Dan Lanciani" <ddl-cctech at danlan.com>
>"Dwight K. Elvey" <dwight.elvey at amd.com> wrote:
>| I just meant that CP/M has a nice table that one can replace.
>I don't think it's nice at all.  It was yet another piece of meta data
>that you needed to correctly read a foreign disk.  Combined with vendors'
>tendencies to use other than DRI's recommended allocation parameters it
>made interchange of anything other than SS/SD 8" disks a nightmare.  Which
>reminds me...  Somewhere on one of the disks I just finished imaging is a
>program I wrote to dynamically patch the BIOS in memory with parameters
>for various foreign disks (as stored in little parameter files).  This
>was primarily for soft-sectored disks, of course.
>|not sure if I've ever seen anything like that in HDOS, although
>|it might be there.
>Happily it is not.

Hi Dan
 I see your point from this perspective as well. I think that
CP/M chose this route because at the time some disk controllers
were not able to generate interleaved disk. In order to improve
perfomance, they chose to deal with it this way. ( I have just
such a controller on my IMSAI ).

>				Dan Lanciani
>				ddl at danlan.*com
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