System Software (0-6) Pre-Release

In 1984 Apple Computers unveiled their Macintosh computer. It included a new user interface that revolutionized the way people though about computer interaction. Originally referred to as simply "Macintosh System", the underlying OS was a single-tasking disk system for the Motorola 68K CPU. Significant changes were made in MacOS 7.x.

Emulation note: For MacOS 0.x-6.x we recommend the vMac Mini emulator.

It is possible to write Macintosh 400k/800k images to a real disk using a Kryoflux.

Note: Wikipedia's/Apple's Developer CD Classic Mac OS "System Software" numbering scheme is GARBAGE and should NOT be used.

Twiggy Mac OS is a development pre-release used with the 5.25" Twiggy prototype Macintosh.

This version will not run on a normal Macintosh or emulator, and used Apple's 5.25" Twiggy floppy disk. A special Twiggy Macintosh emulator is included so you may try it for yourself.

There are also two "Sony Test" pre-releases, that run from a 3.5" disk. One includes a late version of the original Finder prototype renamed as "Flounder".

A detailed review can be found here: Toastytech Apple Macintosh Twiggy Pre-Release

Product type
Release date
Minimum CPU
Minimum RAM
User interface


Download Name Version Language CPU File type File size
Apple MacOS Twiggy Pre-Release (5.25-Twiggy) Twiggy Prototype English m68k 5¼ Floppy 428.78KB
Sony Test 6.9 with Flounder 4.4 (3.5-400k) 6.9 English m68k 3½ Floppy 366.93KB
Sony Test 7.0 with Finder 4-Oct-83 (3.5-400k) 7.0 English m68k 3½ Floppy 162.43KB


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