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Year released:
[www].se [ftp].se [mirror].us
servant-multimac.img_.hqx (350.38 KB)
MD5: 4bfb2a3c619befab5ca46b79b7852982
For System 1 - 5
This app works with: Mini vMac

Of all the early Macintosh multitasking solutions, the most astounding and puzzling event was the sudden appearance of Multi-Mac in late 1985 - after Switcher, but well before Servant and MultiFinder. It had a copyright from an unknown company, "Aubrac Systems", and was written by a previously unknown developer "Jwa van der Vuurst". Since the code makes hundreds of undocumented calls to the ROM, many people suspect the claimed authorship to be an alias, covering clandestine development from inside Apple. If not, Multi-Mac certainly represents a monumental feat of reverse engineering! It works only with a 512K mac and the 64K ROMs, and was never updated.

Some of the features of Multi-Mac anticipated future Macintosh systems by several years! For example:

  • Disk caching, which speeds up the Mac significantly,
  • Aysnchronous file management allowing, for example, background file copying by the Finder in System 4!
  • True simultaneous execution of multiple programs, each sharing the screen,
  • A drop-down application menu on the right hand end of the menu bar,
  • Lazy menus, i.e. the menu drops when the mouse passes over it without requiring a click.

Stories of Early Mac

For many Macintosh users with brand new Fat Macs equipped with 512K of RAM, this System enhancement made the efficiency promised by computers possible. Dave Morris, in his contemporary review of Multi-Mac, wrote, "It was possible for instance to be downloading a long file via a telecom program, and writing a letter in MacWrite at the same time you were printing out a spreadsheet." Multitasking was possible on the Macintosh without the additional hardware Apple claimed was necessary. The sheer brilliance of its capabilities and the complex ROM calls made by this application led many to believe that Andy Hertzfeld was behind this enhancement to the Macintosh experience.

Josh Burker

Having remained a mystery for decades, the author came forward in September 2011 by posting a comment to

I was the author of Multi-Mac. No, I didn't work for Apple, but I did demo it to Apple at the time. I had bought a mac-512 in 1985, and got frustrated by the performance of the floppy disk.

I had a lot of experience back in Holland disassembling z80 machines and implementing my own OS(JWA-Forth) on them. So it wasn't too hard to disassemble the ROMs of the mac. My first patch was to implement a disk caching system and also allow it to cache floppies that where not in the drive. So you wouldn't have to swap floppies all the time.

Then I got this idea. The desk accessories where able to run in parallel to the application. Every application would call SystemEvent. So i made each application look like a desk accessory to the other applications. The one problem left was memory management. Since the mac was only using 24 bit addressing, i used the upper 8 bits in each handle to remember who owned the allocated memory. The running application would have the bits set to 0. New memory allocated defaults in that state. Switching to a different app required patching the upper 8 bits of every memory handle. 0 -> active app# and next app# -> 0. It actually worked really well. I demo-ed it at apple and had 5 apps running at the same time, using 2 floppy disks on one drive. It would calculate the next chess move in the background while running MacWrite in the foreground and keep spreadsheets and other programs running in the background. While Apple was very impressed, they had no interest in buying it (Andy didn't thing my memory handling would be very stable), and I knew that releasing it would have me having to keep up with all the new ROM releases from Apple in the future. We had a small company(IIS) at the time that was writing Insurance software for the HHC (from Friends Amis)and really couldn't do without me. We did come up with a great marketing phrase at the time though: "Now your Mac can walk and chew gum at the same time!"

My name is Johannes Willem Antoon van der Vuurst (Hans), if you have any questions.

Architecture: 68k

Requires a 64K ROM.

Extensive testing has revealed that Multi-Mac will work with the following versions of System Software:

Finder 4.1 & System 2.0
Finder 4.1 & System 3.2
Finder 4.1 & System 3.3
Finder 1.1g & System 2.0
Finder 1.1g & System 3.2
Finder 1.1g & System 3.3


Euryale's picture
by Euryale - 2009, September 4 - 9:23pm

Wow, this is TRULY abandonware.