Catweasel opinions, sources of info etc.

[Jim Leonard]

Vintage Computer Festival wrote:
>>On Tue, 2005-03-08 at 20:40 -0600, Jim Leonard wrote:
>>
>>>Or, you could try a simple parallel cable and Disk2FDI:
>>>http://www.oldskool.org/disk2fdi
>>
>>How does that work? From past discussions on this list, the PC parallel
>>port isn't fast enough to sample the bitstream from a floppy drive...
> 
> It doesn't work over the parallel port: it uses the actual PC floppy drive
> to read GCR disks natively using an incredibly clever trick.  Read the

Right, it uses actual PC floppy drives connected with a special cable (very 
simple to wire up) that connects it to the parallel port.  Essentially, the 
parallel port becomes a high-speed floppy controller.  It is done this way 
because the regular floppy controller can't do some of the things that are 
required to 100% exactly image a diskette (like pass all of the information off 
the controller).

> information in the downloads on how it works.  You can get the trial
> version for free, but it requires two drives to work.

Yes, and the two-drives thing is something that is one of the most clever hacks 
I've ever seen -- you can't get the floppy controller to pass all bits through 
to the CPU to write to a hard disk file, but you CAN use a pass-through method 
of the controller to write them to sectors on a formatted diskette on another 
drive.  When done, the program then writes a FAT to the diskette and assigns a 
file to where the sectors were written.  Seems like a kludge but is actually 
kind-of brilliant.

I should note that, since FDI images are 100% exact bitwise dumps, they aren't 
exactly easy to read (they're not nice clean formatted-track-and-sector images) 
so getting them translated back to an actual floppy diskette is not currently 
possible (since nobody has written the software to do so yet).  However, they 
can be parsed: WinUAE has native support for FDI images and they work fine.  I 
personally verified this by dumping a copy-protected Amiga game disk (on my PC, 
how strange!) and then mounting and booting off of the .FDI image.  Worked 
perfectly, copy-protection and all.
-- 
Jim Leonard (trixter at oldskool.org)                    http://www.oldskool.org/
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