Osborne-1 SD format

From: Dwight K. Elvey <dwight.elvey_at_amd.com>
Date: Mon Feb 21 20:10:56 2005

>From: "Eric Smith" <eric_at_brouhaha.com>
>Steve Thatcher wrote:
>> all Intel did was to use the same basic 3270 format and double the number
>> of sectors to make the OS changes easy. The gaps between real data did not
>> get as big from SD to Intel's DD.
>Intel made more changes than that. In addition to the use of M2FM and
>and different gap sizes, the index mark, ID address mark, data mark, and
>deleted data mark don't match standard FM or MFM. The gap and PLO sync
>bytes are different as well.

Hi Eric
 I'm almost sure that the headers of the sectors have something
different in them as well. I recall looking at it and thinking
that it was just something else that needed special handling.

>It's documented in the disk controller manuals. For instance, see
>pages 4-25 through 4-31 of the iSBC 202 manual:
> http://bitsavers.org/pdf/intel/iSBC/9800420A_SBC202hwRef_Sep77.pdf
>Or pages 1-4 through 1-11 of the Intellec Double Density Diskette Operating
>System Harndware Reference Manual:
> http://bitsavers.org/pdf/intel/MDS2/9800422_M2FMdskCtl_Jun79.pdf
>DEC, on the other hand, really did just subsitute a slightly modified
>MFM data field for the FM data field on their RX02 disk system. The
>details are in the RX02 Floppy Disk System Tecnical Manual, pages 1-10
>through 1-14:
> http://www.chd.dyndns.org/rx02/ek-0rx02-tm-001.pdf
Received on Mon Feb 21 2005 - 20:10:56 GMT

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