Using an internal Superdrive or 800K macintosh floppy on IIgs

On Tue, Jun 25, 2013 at 11:55 AM, Al Kossow <aek at bitsavers.org> wrote: Thanks for this, Al. I was looking at the multicolumn table "pin assignment on Apple floppy disk drive" to see some of what I was looking for when I recently asked about using a double-sided floppy on an original 128K Mac with original (MFS-only) 64K ROMs. I see the following differences between "single sided Mac" and "double sided Mac" which must be part of the whole "red stripe"/"yellow stripe" floppy cable thing... DB-19 pin 9 / 20-pin-cable pin 17 /ENABL2 in other drives/machines Mac single-sided and double-sided: "+12V in drive / No Wire" DB-19 pin 5 / 20-pin-cable pin 9 -12V in most cases in other drives/machines "no wire" on Mac drives (-12V on host) DB-19 pin 10 / 20-pin-cable pin 19 or 20 WRPROT in most cases in other drives/machines Mac single-sided: PWM (on 20) Mac double-sided: "N.C. in drive/PWM in Mac" (on 20) So... it looks like a wire or two differences in the power, the functional difference between single-sided and double-sided is the PWM line on pin 20 on a single-sided drive is a No Connect on a double-sided drive. I do remember that the 400K (single-sided) drives changed pitch as they ran the heads in and out, obviously controlled by the PWM line from the Mac, and that the 800K (double-sided) drives did not change pitch. My goal is to put together a 128K Mac with an internal and an external floppy drive for exhibit/display purposes (mostly to show what a PITA it was to use the original, unexpanded Mac). I have a fully-working Mac with keyboard and mouse and functional internal floppy. The thing I'm trying to do is add a single external floppy for outboard data and applications to minimize the "floppy dance" (and I think historically it was somewhat common to bite the bullet and pay for a second floppy drive when hard drives were unavailable or nearly as expensive as the machine itself). I know they quickly dumped the 128K Mac in favor of 512K of RAM (and equally as quickly standardized on 1MB with the dawn of the Mac Plus), but the point of the exercise is being semi-productive with 128K and no hard disk. This being an entirely optional exercise, I'm not likely to scour eBay for an old M130 drive. I do have the shell of an M130 from a drive that died 25 years ago, so I'm willing to entertain hiding a double-sided drive mech inside the "correct" enclosure. If a newer drive mech will sufficiently act like an older one (doing the right thing with linear bit density as the heads step in and out, and not caring that only one head is ever selected), then I might be able to pull this off. Alternately, I don't mind picking up an inexpensive working M130 (even if it needs cleaned/lubed) but they aren't as common as they once were. I guess as long as I don't route +12V or -12V where it's not welcome, the other differences aren't likely to break anything, but if anyone has any advice or suggestions on mixing and matching drives and the most ancient of Macs, I'm willing to listen and save any time and frustration trying things that are known not to work. -ethan