Date: Tue, 29 Nov 2005 22:15:25 -0800 (PST)
From: Fred Cisin <cisin at xenosoft.com>
Subject: RE: "Market" for old macs?
>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 Tue, 29 Nov 2005, Chuck Guzis wrote:
The bigger problem isn't that it's GCR,
but rather that it's also variable
rate GCR. I'd remove the quotes from "impossible" on this one, although,
maybe with a razor blade and a magnet and a VERY steady hand...
How fast can you turn the MOTOR ON line on and off? :-)
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), 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.
My main obstacles to cloning the thing is an affordable source of the
WD92C32 and the time and method to extract the logic of the GAL.
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.
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?
The thing that particularly arouses my curiosity is that the Laptop
125 has no SCSI port, nor external floppy port. But it has a Hirose
brand DX10-28 connector (looks a lot like a mini-centronics). That
connector can interface to an external floppy or external SCSI
controller. The interface point for the external floppy is the
85C30. The interface point for the SCSI controller is a 53C80. So
I wonder what the Outbound is using for signals on that 28 pin
connector that will work for both of those interfaces and make some
kind of sense to the Mac guts at the other end.
Jeff Walther
