[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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