Steve Chamberlin Adds Apple Macintosh MOOF Support to the Flexible Floppy Emu's Firmware

Steve Chamberlin's Floppy Emu, a compact floppy disk emulator board designed for vintage Apple computers, has received a major update: support for the new MOOF Macintosh disk image format.

"MOOF is a new disk image format for 3.5-inch Macintosh floppy disks, designed by John K. Morris, with the goal of capturing all the low-level disk information needed for copy-protected software," Chamberlin explains of the emulator's latest feature. "It's the Macintosh equivalent of a WOZ disk image for Apple II computers."

Previously, using the Floppy Emu on a Macintosh system — one of the systems supported alongside the Apple II range and the Lisa — typically required a byte-level disk image. This is fine for most software, but not all: as an anti-copying measure it wasn't unheard of for software distributors to insert deliberate errors into disks, detectable in software but not captured by byte-level imaging tools — preventing copies, or disk images loaded into an emulator, from running.

"A MOOF disk image is a bit-level representation of the disk as it's physically implemented in the floppy media," Chamberlin explains. "It's everything on the physical disk, including the empty space between sectors, the headers and footers, and GCR 6&2 encoded data or whatever non-standard encoding the developer may have chosen. When people asked me about MOOF in the past, I said it was impossible for Floppy Emu to support bit-level 3.5-inch disk images because there wasn’t enough RAM to store a complete track at the bit level. So what kind of black magic makes this possible now?"

That "black magic," it transpires, is a RAM-saving trick to free up space: in the latest firmware, the emulator loads only a single side of a MOOF image from the SD Card at once — switching to the other side on-demand. "There's a delay for SD card access when switching to track 0 side 1," Chamberlin explains. "In theory this might cause software errors or copy-protection failures, since there’s no equivalent delay with a real disk. But in practice, I don't think it’s a problem."

The new feature is available now as a firmware update, which will come pre-loaded on all newly purchased Floppy Emu Model C hardware — but it does come with a few caveats. The first is that two titles — The Ancient Art of War and The Surgeon — still fail their copy-protection checks, and MOOF images are loaded read-only.

Support is also only included for 400kB and 800kB MOOF images. "RAM limits are one of several reasons you’ll probably never see 1440[kB] MOOF support on this hardware," Chamberlin notes. "But that's no great loss since the era of media-based copy protection had mostly ended by the time 1440[kB] disks were introduced."