[Coco] Re: Disk controller summary?

[Roger Merchberger]

Rumor has it that KnudsenMJ at aol.com may have mentioned these words:

>I was once part of a reverse-engineering project where we had a  competitor's
>8" floppy disk, with no idea of its format or underlying OS.   We built an
>interface to just sample the flux transitions under the read head,  which 
>came
>thru as a string of 1's and 0's.  A friend built the hardware  that sampled
>these data and saved them as a file.
>
>I wrote a simple software state machine to track the flux transitions and
>decode into actual 0s and 1s in terms of the MFM encoding.  Didn't 
>take  long to
>combine these into bytes, and figure out it was CP/M.

The guys over on the classiccmp mailing list would like to talk to you... ;-)

They're discussing just this very topic WRT backing up and restoring 
classic media (floppy primarily).

Offtopically, would this technique work with GCR, too?

>Do any of these PICs, AVRs, or HC11s clock fast enough to sample the flux
>transitions?  ISTR they were in the 100s of KHz range, so probably  can.

Should be able to - Most AVRs can clock at 8Mhz, some can clock up to 
16Mhz, and the instruction set is almost all 1-clock-per-instruction; so 
_in theory_ a 16Mhz AVR runs at 16 Mips, in practice, you could quite 
probably get 13-15 Mips.

Laterz,
Roger "Merch" Merchberger

--
Roger "Merch" Merchberger  --  SysAdmin, Iceberg Computers
zmerch at 30below.com

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