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Year released:
[www].se [ftp].se [mirror].us [mirror].de
sim020_0.1.sea_.bin (28.75 KB)
MD5: 8a2cb82044debd81f7d51f8900f699fb
For System 6.x - System 7.0 - 7.6
[www].se [ftp].se [mirror].us [mirror].de
This app works with: Mini vMac

Sim020, aka '020 Simulator, was an experimental system utility created in 1990 by Boris Klug in attempt to show that a computer with the original Motorola 68000 processor can emulate the Motorola 68020 processor, even though the 68020 is newer than the 68000, by converting possible 68020-only instructions in the Finder code that would otherwise cause an "illegal instruction" bomb screen on a 68000-based Macintosh to the equivalent 68000 code before execution.

The original release of Sim020 in 1991, version 0.1, was incomplete, and these three notes were provided in the Readme file to show part of the fact that version 0.1 is incomplete:

  • works only with Finder
  • Some 68020 cmds are not implemented yet (TRAPcc, CHK2, some bitfields)
  • This version is not full tested with all 68020 cmds. It is possible that there are some unknown bugs in it.

The Readme file said that Boris Klug and Frank Siegert were working on a "full version" of Sim020 which would fix a lot of the bugs and introduce a lot of new features, but the "full version" was probably never released, so Sim020 is considered abandonware.


Architecture: 68k


reukiodo's picture
by reukiodo - 2015, November 9 - 6:12am

Also, if you check the box 'Use 68020 in system info' after adding the control panel (not loaded on system boot), then click Restart many times in the "Finder invalid address" error prompts, eventually you'll get a seizure screen where it flashes the error box endlessly.

reukiodo's picture
by reukiodo - 2015, November 9 - 2:03am

This causes "unimplemented trap" errors in System 7.5.5 Finder on a 68000 CPU (Macintosh Classic).