I’ve just merged in a change to FluxEngine, my open-source and easy to build USB floppy drive interface, which will let you use it to write Macintosh 800kB GCR disks using a normal PC drive.

For context: the FluxEngine is a off-the-shelf, unmodified Cypress PSoC5 development board, costing $10-$15 (plus Cypress’ exorbitant shipping, sadly). A single component is soldered to it, which is the floppy drive connector. (You can get away with a row of header pins if you don’t have one.)

closeup of the board with connector attached

When programmed with my software, it becomes a USB flux-level floppy drive interface, capable of reading and writing raw pulsetrains from and to a normal PC floppy disk drive. The client software will then decode the flux information into disk images, or encode disk images into pulsetrains for writing back to the disk.

Currently it supports a wide variety of disk formats, including the ubiquitous FM and MFM IBM scheme PC-compatible disks, but also oddities like the FB-100 (with two sectors per track) or the Brother GCR word processing format (240kB per disk, with two different weird GCR encoding schemes). Because all the decoding happens in software, it’s not constrained to a limited selection of formats by the floppy drive controller logic — it’s theoretically capable of reading anything physically compatible with the drive. It can even handle CLV formats, where the drive changes speed: the PC drive always spins at 300rpm, but instead the pulse frequency changes. The software decoder sees no problem with this.

However, it’s also possible to encode disk images back into pulsetrains, and write them back to the floppy disk. I’ve been using this successfully on Brother word processor disks for a while (this was originally why I built it). What I’ve just done is add support for 800kB Macintosh GCR disks, and tested them on my new PowerBook 150.

What this means is that you can now make your own Mac Plus or Mac SE boot disks, from DiskCopy 4.2 images downloaded off the internet, without needing to either buy them off eBay, exchange them in a shady pub, or buy a more recent Mac with a SuperDrive.

You do still need to build a FluxEngine, though…

Main FluxEngine page

See the main FluxEngine page for more information.

It’s had limited testing, but the written disks work fine on my PowerBook 150, and I’ve had a report from someone who’s successfully booted a Mac Plus using a FluxEngine-written disk. I’d appreciate any user reports — please file a github issue via the link on the main page.