Change notes

1.0

The first release. Six Macintoshes boot to the Finder, with sound, disks you can write to, and a pointer that moves.

The machines

Mac 128K, Mac 512K, Mac Plus, Mac II, Mac SE/30 and Mac IIci. Each is emulated from its own ROM rather than approximated: the 68000, 68020 and 68030 processors with their real exception behaviour, the 68881 and 68882 floating-point units, the 6522 VIAs, the real-time clock and its parameter RAM, ADB keyboards and mice, the IWM and SWIM floppy controllers, NuBus video, and the 68030's memory management unit as far as classic Mac OS actually uses it.

Memory sizes are only offered where they have been verified booting — which is why the lists differ per machine and why a few sizes are absent.

Sound

The compact Macs' DAC, reading its buffer out of RAM a byte per scanline. The Mac II family's Apple Sound Chip in both of its playing modes: the FIFO the Sound Manager pours samples into, and the four-voice wavetable the ROM uses for the startup chime. The chip's half-empty interrupt reaches the processor properly, so software that refills on interrupt works.

Disks

Floppy images (DiskCopy 4.2 and raw dumps), hard disk images with an Apple partition map, and CD-ROMs — .iso, .toast, .cdr — which mount read-only and are told so properly, so the System marks them locked rather than deciding the disc is faulty.

What the emulated Mac writes goes back to the image file, so work saved inside it survives being switched off. A DiskCopy image's header checksum is brought back into line when the writing stops, so other tools don't call a perfectly good image damaged.

Disks put in while the machine is running are noticed and mounted, and a machine sitting at the blinking disk icon will start from one inserted then — no restart needed.

The application

A real Mac application: universal for Apple silicon and Intel, no dependencies beyond macOS itself, and nothing to install. Save and restore the whole machine to a file, make formatted blank floppies, run full screen, and choose the machine, its memory, its screen and its clock in Settings.

Signed with a Developer ID and notarised by Apple — both the application and the disk image, each with its ticket stapled on — so it opens with a double-click, offline as readily as online, with no right-clicking and no Terminal.

Known limitations

• No SCSI controller. Hard disks and CDs are served by intercepting the disk driver instead, so the volumes are real but the bus underneath them is not.
• No AppleTalk.
• A disc carrying only ISO-9660 — no Mac volume — cannot be mounted. Hybrid discs, which is what Mac software shipped on, mount from their Mac side.
• The Mac II will not take 8MB, and the SE/30 will not take 64 or 128MB. Both are understood: the memory sizing those ROMs perform disagrees with how this emulator lays those configurations out.
• ROM images are Apple's and are not included.