Re: sun remarketing disk format

David is one of the great unsung heroes of the classic computer world. He was gracious and tireless in helping me get the MFM emulator working with NorthStar and Corvus H-Drive disk formats. Truly an invaluable contributor to retro-computing.

On Friday, January 20, 2017 at 2:20:19 PM UTC-5, Al Kossow wrote:
>
> I managed to read some tracks from a Kalok MFM drive, and Dave Gesswein
> decoded the format
>
> The drive controller has rev C firmware, and uses a board that looks more
> integrated than the
> pictures of the one on bitsavers, so I uploaded the firmware and those
> pictures. Interesting that
> the drive apparently has two cylinder 0's.
>
> I'll make another attempt at reading my drive later today.
>
> It would be nice to add firmware disassemblies to the stuff on bitsavers.
>
>
> from Dave:
>
>
> Code up in testing if you wish to try. In looking further its not seek
> error, they are being really irritating. The drive has two cylinder 0's.
> On the first read it isn't interleaved and after the seek it is
> interleaved.
> My code doesn't have much hope of handling that cleanly.
> Head 1-3 on the first cylinder 0 look like they aren't formatted the same
> as zero.
>
> Try reading with
> --sectors 17,0 --heads 4 --cylinders 615 --header_crc
> 0x2605fb9c,0x104c981,32,5 --data_crc 0x84a36c27,0x104c981,32,5
> --format OMTI_5510 --sector_length 532 --retries 50,4 --drive 1
>
> without --ignore_seek_errors it should read the first cyl 0 then
> see the second and assume a seek error and move on to cyl 1/2.
>
> With --ignore_seek_errors it will overwrite the first cyl 0 with the
> second
> and ignore mismatches between the expected cylinder and actual. Data will
> be written to cylinder read from header.
>
> You can change the ,5 to ,11 on the crc to increase the ECC to 11 bits to
> try to recover more sectors. OMTI said 5 bit correct but others have
> said 11 bit with 32 bit ECC. Larger number increases chance of miscorrect.
>
>

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