Emulation on the Amiga

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This article is about the Amiga emulating other computers. For information on emulating the Amiga itself, see Amiga emulation.

The Amiga computer can be used to emulate several other computer platforms, including legacy platforms such as the Commodore 64, and its contemporary rivals such as the IBM PC and the Apple Macintosh.

Contents 1 MS-DOS on Amiga via Sidecar or Bridgeboard 2 Amiga Transformer 3 Mac OS on Amiga 4 Signetics-based Machines

[edit] MS-DOS on Amiga via Sidecar or Bridgeboard

MS-DOS compatibility was a major issue during the early years of the Amiga's lifespan in order to promote the machine as a serious business machine. In order to run the MS-DOS operating system, Commodore released the Sidecar for the Amiga 1000, basically a 8088 board in a closed case that connected to the side of the Amiga. Clever programming (a library named Janus, after the two-faced Roman god of doorways) made it possible to run PC software in an Amiga window without use of emulation. At the introduction of the Sidecar the crowd was stunned to see the MS-DOS version of Microsoft Flight Simulator running at full speed in an Amiga window on the Workbench.

Later the Sidecar was implemented on an expansion card named "Bridgeboard" for Amiga 2000+ models. Bridgeboard cards appeared up to 486 processor variants. The Bridgeboard card and the Janus library made the use of PC expansion cards and harddisk/floppydisk drives possible. The bridgeboard card was manufactured by Commodore, later third party cards also appeared for the A500/1200 expansion slot such as the KCS Powerboard.

Eventually, full-software emulators, such as PC-Task and PCx allowed Amigas to run MS-DOS programs, including Microsoft Windows, without additional hardware, at the costs of speed and compatibility.

[edit] Amiga Transformer

Early Amigas could use a program called Transformer to emulate a PC via software, however it was extremely slow; The 'Landmark' benchmark rated it as a 0.3 MHz 286, far slower then the 4.7 MHz of IBM's oldest and slowest PC. In addition, it would only run on Amigas using the 68000 microprocessor, and would not run if the Amiga had more than 512K of RAM.

[edit] Mac OS on Amiga

Also introduced for the Amiga were two products, A-Max (both internal and external models) and the Emplant expansion card. Both allowed the Amiga to emulate an Apple Macintosh and run the Macintosh Operating System. It required an Apple Macintosh ROM image, or actual ROMs in the case of A-Max, which needed to be obtained from a real Macintosh. The user needed to own the real Macintosh or Mac ROMs to legally run the emulator.

In 1988 the first Apple Mac emulator, A-Max, was released as an external device for any Amiga. It needed Mac ROMs to function, and could read Mac disks when used with a Mac floppy drive (Amiga floppy drives are unable to read Mac disks. Unlike Amiga disks Mac floppy disks spin at variable speeds, much like CD-ROM drives). It wasn't a particularly elegant solution, but it did provide an affordable and usable Mac experience.

ReadySoft, makers of A-Max, followed up with A-Max II in the early 1990s. A-Max II was contained on a Zorro-compatible card and allowed the user, again using actual Mac ROMs, to emulate a color Macintosh. In fact, an Amiga 3000 emulating a Mac via A-Max II was significantly faster than the first consumer color Mac, the LC.

Over time full-software emulation was available, but you still had to get a ROM image. Example emulators include ShapeShifter (not to be confused with the third party preference pane ShapeShifter), later superseded by Basilisk II (both by the same programmer who conceived SheepShaver, Christian Bauer), Fusion and iFusion (the latter ran classic Mac OS by using a PowerPC "coprocessor" accelerator card).

This form of emulation has been said to equal or better the speed of a Macintosh with the same processor, especially with respect to the m68k series due to real Macs running in MMU trap mode, hampering performance. Moreover, in the period when no new 68k Mac models were being developed and the majority of Mac software was not natively available on PowerPC Macintosh yet (but only runnable through a slow 68k emulation), the fastest "Macintosh" machines around were actually by far Amiga computers with 68060 CPUs running ShapeShifter or Fusion.

One should note that although Amigas were very successful at emulating Macintoshes, it was never considered to be a Macintosh clone as it could not use Mac OS as a primary operating system.

[edit] Signetics-based Machines

The Amiga is one of only two platforms with a dedicated emulator of Signetics-based systems, namely, the Emerson Arcadia 2001, the Interton VC 4000, and the Elektor TV Games Computer.