Mac Plus 3.5" drive with iigs

[Nebular]

I just acquired a iigs from our local e-waste. It boots and everything looks great on it, however I have nothing to run on it. It has a 5.25" drive, but I have no disks, nor a way to write disks unless there's a way to write an image from a vintage PC. I have no money to buy disks or emulators, which is one of the reasons I'm raiding e-waste. I do however, have a couple mac pluses, an M0130 external drive, a couple LCIIIs, and a bunch of DD disks. I'm wondering if there's a way I can use the Mac Plus Drive on the iigs. The cable from the M0130 fits into the mac plus drive, but when powering on, I get no noise or activity light like I do with the 5.25" drive.

Is it possible?

 

[Gorgonops]

Not really, unfortunately. The 3.5" drive that's compatible with the IIgs has a little daisy-chain board inside of it that's necessary for the IIgs to recognize that there's a 3.5" drive attached to it. FWIW, I don't *think* you'll kill the IIgs' drive port by hanging the Mac drive off it, but the reverse may not necessarily be true because the 3.5" and 5.25" drives use some of the interface lines in completely different ways. I don't *think* it's going to kill anything but technically you might be putting stepper-motor-drive-strength signals against the control register inputs on the Mac drive when you plug it straight in like that.

(There is a warning that plugging the 5.25" drives into a Mac *will* kill the Mac's drive port; I think it's because they short out the PWM signal, not anything related to the control line/step line difference, but I'd still be careful.)

On the bright side the necessary A9M0106 drive tends to be one of the cheapest and most common external Apple floppy drives, but it still looks like the going rate for one on eBay today is in the $40-$50 ballpark. Maybe someone here has a surplus one they would be willing to let go cheaper.

 

[Fizzbinn]

I'm pretty sure the M0130 drive won't work with Apple II. I believe these are the only 3.5 Apple external floppy options that work with the IIgs built in floppy controller:

• "Apple UniDisk 3.5 Drive" A2M2053
  
• "Apple 3.5 Drive" A9M0106
  

They are both 800K drives but I think the "Apple 3.5 Drive" maybe faster, It's also compatible with Macs, which the UniDisk is not.

 

[Nebular]

Any possibility of adapting the pins on the cable? Is there somewhere I can find the pinout for the port on the iigs and the port on the drive itself?

 

[Gorgonops]

There are active components on that daisy chain board. You *might* be able to use Big Mess O' Wires' recreation of said board:

https://www.bigmessowires.com/shop/product/daisy-chainer

to interface the bare mechanism inside your 800k drive to your IIgs but that costs about as much as an A9M0106 would.

There are probably enough details in the 7-part blog series BMOW published while designing that board to make your own copy of it but, again, it requires active components and apparently does some kind of nasty tricks to do what it does. Again, the IIgs' disk port actually supports two fundamentally incompatible types of disk drives(*) by selectively playing games with how it defines the interface signals. The final design he went with relies on a microcontroller to replace a goofy state machine involving some one-shot triggers and other voodoo.

(* Strictly speaking it actually supports three types, because "Smartport" devices are yet another type of animal.)

 

[OleLila]

Once you get it set up ADTPro is pretty convenient.

 

[Gorgonops]

Once you get it set up ADTPro is pretty convenient.

And yeah, that'll work fine for getting things onto 5.25" disks if you can lay hands on some. That'll pretty much limit you to running Apple IIe software, but it's better than nothing.

 

[Nebular]

OK so I went through the BMOW blog posts pertaining to floppy emu. according to this post: https://www.bigmessowires.com/2015/04/01/apple-ii-800k-3-5-disk-emulation/#comments the only thing that is needed to get a Mac 800k floppy to work on the iigs is to tie pins 16 and 20 together and it will work as the only drive connected to the computer (Which is all I care about at the moment). So I take the DB-19 cord, do some continuity testing to match the pins on the iigs to the pins on the floppy, tie 16 and 20 together, and I'm good to go until I can get a Floppy EMU or an actual 3.5" external drive. All the complicated stuff is only in the actual daisy chaining so the computer knows which drive is where and what kind.

 

[Gorgonops]

Be sure to update if that actually works as a practical workaround. I do suspect the fact the 800k Mac drive doesn't have an eject button is going to be something of an issue. Under GS OS you can issue an eject like you can with a Mac, but (practically speaking) you're not going to be running GS OS without a hard disk, just games and other booters.

 

[Nebular]

The 800k drive does have an eject button. It's just hidden behind plastic.

 

[Nebular]

Well, it seemingly works. Taking the cable from the M0130 and connecting pin 20 and 16 together gives me seek on startup, no error on screen anymore and the drive is spinning.

So, what's the best way to get working 3.5" disks for this? I have a USB LS-120 drive that seems to be able to take anything I throw at it. I was able to make 800k mac disks from images using rawwrite that my LCIII could read. At the same time I have an LCIII with a superdrive so I can copy over any images out there and image them using the Mac floppy drive itself if that is easier.

What's the best way?

 

[sstaylor]

Wow, I'm really surprised that any USB drive could write 800K disks.  Good to know.

 

[IlikeTech]

It's not that the USB drive can write GCR 800k disks.  It can write 1.44 MB disks.  It just happens to work writing 800k images that don't take up the full disk.  I doubt they would work on a machine without a superdrive.