PC floppy doing Mac 800K; Was: "Market" for old macs?

[Fred Cisin]

> >>  >I'd LOVE to hear from anybody who is successfully formatting and writing
> >>  >GCR with a PC (without adding in a "flux transition" based additional disk
> >>  >controller (such as Catweasel or COPYII Option Board)
> >>  >It is "impossible".   (VERY difficult)
On Wed, 30 Nov 2005, Jeff Walther wrote:
> The Outbound Laptop Model 125 (ca. 1989 Mac laptop clone) uses a
> Citizen brand PC type laptop floppy drive.  It reads and writes 800K
> Mac floppies as well as 1.4 MB floppies on both platforms.   However,
> it has a controller card on the end of the floppy drive.
> The main components of the floppy controller card are an 85C30,
> WD37C65, WD92C32 (confused as to why this is there, since the 37C65
> has a data separater built in),
because it is BYPASSING the 765 for read and write of 400k/800k GCR.
> an LS624 voltage controlled
> oscillator, a Xicor X9103 digital potentiometer, a 27C256, and a
> GAL16V8.   There's a little bit of other standard 74 series logic on
> board as well.

 . . . to add "flux transition" capabilities to the 765

> I find it interesting that back in 1989 someone had already found a
> way to make a PC floppy work as a Mac floppy, though with a double
> handful of chips.

THE PROBLEM HAS NEVER BEEN THE DRIVE.
The problem was, and is, the disk controller.
I can do Apple][ with a Tandon TM100-2,
I can do Mac with damn near ANY 3.5" drive.
BUT ONLY WITH SIGNIFICANT MODS to the operation of the FDC.
(Apple Turnover with my software, or Central Point CopyII DELUXE Option
Board with their software, or Cat weasel, or adding a raw data in
(DISK2FDI))

> I'm not quite sure what kind of interface the Outbound uses to the
> floppy drive, though.   Obviously, there's no SWIM chip in the
> Outbound.  So did the original designer (Doug Swartz?) cobble up a
> SWIM from 74 series logic or does the controller on the floppy negate
> the need for the SWIM?

When you trace that out, then you will understand why an unmodified PC can
not do Mac GCR.

--
Grumpy Ol' Fred     		cisin at xenosoft.com