# m68k Macintosh

In the history of computing, Apple has its own little timeline. Stuff it did
was largely "in its own way" until in converged with PCs with the introduction
of Intel Macs. As far as Dusk is concerned, we can divide its legacy in roughly
four eras:

1. Pre 32-bit
2. m68k Macs
3. PowerPC Macs
4. EFI Macs

Pre 32-bit is out of scope, Collapse OS being the appropriate OS for them.

m68k Macs is what this documentation page is about.

PowerPC Macs uses OpenFirmware, a world I have yet to discover.

EFI Macs are covered by [hw/efi].

So, this page is about m68k Macs, that is, the initial Macintosh, and the one
that followed it. In other words, anything that has a m68k CPU. The notes below
are little things that I consider important to know when working with those
machines.

## ROM and System 6/7

Much of the OS functionality offered in System 6 and 7 lives, in fact, in a ROM
included in the machine itself.

Mac OS 8 came with the introduction of the PowerPC line. System 5 and before had
fuzzy versioning.

Entry points to this ROM don't seem to be documented very much, but disassembly
of that ROM to figure them out seems straightforward.

TODO: figure this out.

## Floppy formats

HDD connectors for m68k Macs look weird and Apple-specific. To boot an
alternative OS, it looks like using the floppy is the most convenient door. But
it's not a walk in the park, because Mac floppy formats are notoriously
incompatible with PC floppy formats

There is broadly three types of formats being used, the 400K and 800K ones,
using MFS (Macintosh File System). These formats are pretty much off-limit to
non-Apple hardware because they use special timings in the floppy drive to
achieve extra capacity (rather than 360K and 720K).

Luckily, only the earliest Mac models use these formats exclusively. Pretty soon
into the Mac line (TODO: figure out when), 1.4M format support is added and that
format is compatible with PCs (TODO: confirm). The filesystem used in that
format is HFS.

## See Also

* [hw/efi]
* Guide to Macintosh Family Hardware
* Inside Macintosh Volume I to VI. More detailed, hardware-wise, than revamps.
* Inside Macintosh: Files
