Osborne-1 SD format

From: Dave Dunfield <dave04a_at_dunfield.com>
Date: Mon Feb 21 12:38:57 2005

Hi Dwight,

>>In a HD drive, I must select a data rate of 300kbps, and in a DD
>>drive I must select a data rate of 250kbps in order to be able to
>>read them at all...
>Hi Dave
> You know that you can not reliably write to MFM disk
>on a HD drive. Even if you completely bulk erase the disk,
>it still may not work. Get your self a 360K drive!
> The images should be OK that you read.

In my original posting, DD means "360k" - I've been testing with both
kinds of drives.

It's interesting with the Cromemco CDOS disk - the DD area is formatted
to 10 512 byte sectors/track, and in the DD(360k) drive, I can't read
them at all - For this test, I pulled the actual Teac drive that I have
been using on the System-3 (which reads it fine) - it looks like the PC
controller has touble with the tightly spaced sectors.

It (the DD drive) can however read all of the SD sectors in track-0
just fine!

The HD drive reads the entire disk perfectly, EXCEPT for Sector-1 of
Track-0 (the SD track) - it quite reliably refuses to read the first
sector of the SD track. The remaining sectors of the SD track and all
of the DD tracks read OK.

So - I can read the entire disk, however I have to do it on two separate
drives - Unless I can reliably resolve these problems, I think I will
make an option in my disk imager to merge images read of different
drives - In some cases (like this one), it may allow a complete image
to be constructed where it otherwise might not be.

The :-( for the day is that it appears that NONE of the PC controllers
that I have will format a single-density track - I can recreate the DD
tracks just fine (Even with 10 sectors/track), but so far no joy on
formatting and writing that SD system track.

dave04a (at)    Dave Dunfield
dunfield (dot)  Firmware development services & tools: www.dunfield.com
com             Collector of vintage computing equipment:
Received on Mon Feb 21 2005 - 12:38:57 GMT

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