3 Aug
2005
3 Aug
'05
7:32 a.m.
Hi Allison,
Thanks for the info - I'll check it out when I make the changes to support
mixed density reading ... (which may be a while).
Unfortunately
it's looking like mixed sector sizes within one track are
not within the capabilities of the 765 to write - although I could probably
READ them OK (and with a documented image file format, you would at least
have access to the data so you could try to find some other way to recreate
the disks if you had to).
Dave there is a trick.
Looks at FCOPY at Gaby's (unoffical CPM archive). Tim and I developed it
for a project and it's not a generic imager. However we found a few things
out and one is that most 765 implmentations will lock up if in the worng
mode (SD or DD) initially. So to do mixed sector you can't write. However
reading is possible if you first try the mode that doesnt lock first then
switch. In the end you will be recreating the catsweasel. If
you really want to
go to the next level starty with a PC fast enough and skip the whole FDC
chip thing. The next level is a data speperator logic and a shift
register that can be read at the bit rate by the PC and do the needed
pattern regognition (look for sync, address marks and the like), and then
build a literally imaged disk and that can be anaylysed.
I've thought about this - I can do 500khz samples on a PC parallel port,
and with some simple hardware I could get 8x this - but it seems dodgey,
and unless I disable all interrupts (which has it's own set of problems
including losing HD access) there would be excessive real-time jitter.
I've also thought about dropping in something line a 90Mhz (or faster)
ARM - which would give me a much higher sampling speed and better real-
time control than a PC ... but this gets tough to build...
The 2793 would be easy to build, and should handle most soft-sector disks.
The "read track" and "write track" functions of the WD chip allow near
raw-
access to the track data.
But these questions are part of the reason I've not done anything toward
a hardware solution so far.
Regards,
Dave
--
dave04a (at) Dave Dunfield
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