Dual A500/600/1200 internal drives

I recently acquired a vintage Checkmate case with an A500 in (article coming soon!) and wanted to put both a Gotek, and a real floppy drive inside the case. However when I started reading forums and social media posts, it appeared it wasn’t going to be that easy; the “big box” Amigas allow you to have a pair of drives but their floppy drive ports are subtly different to the one on the A500/600/1200 which were only ever meant to support one drive. You’ll see in the images below that there’s differences with the “In Use” and Motor signals, which on these smaller machines are cut back to only ever spin the motor on one drive by tying them together, on the larger machines there’s separate logic-driven signals.

In the past, this was a problem as you couldn’t control the motors individually on each drive. The way the (original) Checkmate 1500 got around this back in the day was literally to loop the external A500 port back into the machine and have an entire, de-cased external drive mounted inside. However there’s a more modern approach which may work, and I wanted to record it here in case it’s of any use to anyone else.

To be clear, I’ve not found a clever way to work two floppy drives off the internal header. There does exist a Micronik adaptor which can do this, however it’s relatively rare as it was sold as an accessory to their A1200 tower kits and it uses a PCB with some logic and signals tapped off a CIA to add back in the missing functions. No, what I’m going to do is to use a floppy drive, and a Gotek. The reason this works is that the Gotek doesn’t just not have or need a motor, but it ignores any motor signals so only the real floppy drive will spin when instructed.

You need a straight through three-header 34-pin cable of a suitable length. You don’t need any twists in the cables, so if you’re grabbing a regular PC floppy cable (or an Amiga one) you’ll need to untwist and re-crimp it. One connector is for the mainboard, and then you’re left with one for each drive. Connect them together and use a Y-splitter to power both drives (don’t worry about the power consumption as the Gotek draws very little) . The Amiga drive should be left with S0 selected, which is going to be the case if it’s the one you’ve been using internally. You should have something like this:

You’ll also probably need to make the following changes to the Gotek:

  • Put a jumper on S1
  • Insert a USB stick containing an ff.cfg file with just the line “interface=amiga” in it

That’s it. You only need to use that config file once, the Gotek will remember it (until you deliberately do a firmware reset on it) but it’s that line that tells the Gotek to correctly report back that it’s present and correct. Normally a Gotek doesn’t need that line and the default “Shugart” mode will work fine on an Amiga, but “interface=amiga” will force it to hand over a Device ID on Pin 34 and make the Amiga aware there’s a drive present in this slightly different setup.

The floppy drive is now DF0, and the Gotek is DF1, and you can use both drives at the same time and even diskcopy from one to the other (or use XCopy to back up your completely original games!)

What you cannot do, however, is make the floppy drive DF1 and the Gotek DF0. This is because only the DF0 motor signal is present, and not logic controlled. The Gotek will ignore this, but the floppy drive – even though it’s DF1 – will see the signal and not be able to stop itself spinning every time you access DF0, and conversely there’s no signal to make it spin when you want it to. This seems to affect the drive detection itself, too, and DF1 won’t show up in the list of attached drives. If you were to use a floppy drive switcher that goes under the CIA chip (effectively the A500++ I’m using has one built in, controlled by two jumpers), then the two possible options are:

  • DF0 Floppy, and DF1 Gotek
  • DF0 Gotek, and no DF1

This seems to cover most use cases, and such a device can be wired to a switch somewhere.

This same trick should work on an A600 and A1200 too, given that the floppy drive headers are identical. Getting both drives inside the case is another matter! Here we’ve got the luxury of lots of space, and the same might be true if you’re using a modern Checkmate, or other aftermarket case. It should be possible to get a gotek inside in a stock case too, with careful insulation, but where you put the USB port, buttons and display may be a challenge.

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