MacWorks Plus was a complete implementation (

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as Ham ...

) of the

Macintosh Plus The Macintosh Plus computer is the third model in the Macintosh line, introduced on January 16, 1986, two years after the original Macintosh and a little more than a year after the Macintosh 512K, with a price tag of US$2,599. As an evolutiona ...

128K ROM on the

Apple Lisa Lisa is a desktop computer developed by Apple, released on January 19, 1983. It is one of the first personal computers to present a graphical user interface (GUI) in a machine aimed at individual business users. Its development began in 1978. ...

and

Macintosh XL Macintosh XL is a modified version of the Apple Lisa personal computer made by Apple Computer In the Macintosh XL configuration, the computer shipped with MacWorks XL, a Lisa program that allowed 64 K Macintosh ROM emulation. An identical ma ...

computer systems, and introduced in August 1988. It was developed for

Sun Remarketing Sun Remarketing, Inc. (originally Cook's, Inc. before 1983) was a retail company that specialized in reselling old Apple Computer software and hardware. It was founded by Robert L. "Bob" Cook in 1979. Apple Lisa In 1985, Sun Remarketing purchas ...

Cache Valley Cache Valley is a valley of northern Utah and southeast Idaho, United States, that includes the Logan metropolitan area. The valley was used by 19th century mountain men and was the site of the 1863 Bear River Massacre. The name, Cache Valley i ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

, under license from

Apple Inc. Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company b ...

, by a contract developer named Chuck Lukaszewski, who was responsible for versions up through 1.1(h), which supported up to Macintosh System 6.0.3. Dafax Processing Corp. with the assistance of Query Engineering, Inc. then further developed the environment to MacWorks Plus II, which continued Macintosh system support up to System 6.0.8 with the ''Basic'' version, and introduced a ''Pro'' version to extend support to the maximum possible for any 68000 processor: System 7.5.5. Prior to MacWorks Plus, the maximum system supported by its predecessor

MacWorks XL MacWorks XL was an Apple Lisa computer program which shipped with the Macintosh XL. It allowed 64K Apple Macintosh ROM emulation so the Macintosh XL could run classic Mac OS programs. History Soon after the debut of the Macintosh, which sold o ...

was System 3.2.

History

The design objective for MacWorks Plus was 100% compatibility with software that ran on the

, which at the time was Apple's flagship product. This was a technically challenging goal because other than sharing the same

Motorola 68000 The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector ...

processor, the underlying hardware architectures of the two systems were radically different. In order to understand how MacWorks Plus worked, it is easiest to divide the discussion into three areas: hardware interface, memory model and bootstrap protocol. These were the hardware-dependent aspects of the

classic Mac OS Mac OS (originally System Software; retronym: Classic Mac OS) is the series of operating systems developed for the Macintosh family of personal computers by Apple Computer from 1984 to 2001, starting with System 1 and ending with Mac OS 9. The ...

at the time. The simplest method of transporting the Mac OS to another machine was to emulate them completely. Once achieved, the much larger hardware-independent code in the 128K ROM could execute with no modification. This is what was done with MacWorks Plus. The goal was made possible by the existence of a hardware abstraction layer in the

Macintosh Toolbox The Macintosh Toolbox implements many of the high-level features of the Classic Mac OS, including a set of application programming interfaces for software development on the platform. The Toolbox consists of a number of "managers," software compone ...

in the original Macintosh ROM, and a hardware

Memory Management Unit A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical ad ...

(MMU) in the Lisa. Through a complete package of device drivers that fully implemented the Macintosh Toolbox Application Programming Interface (APIs), MacWorks Plus essentially tricked the 128K ROM code into thinking it was running on an actual Macintosh. It was also necessary to completely simulate the memory address space of a Macintosh Plus, including the behavior of certain illegal addresses that were deliberately exploited by certain applications (primarily games). Fortunately, while the Macintosh memory manager circuitry was not programmable, the Lisa featured a fully programmable hardware MMU which was a legacy of the minicomputer roots of its designers. Finally, bootloaders were written for all available floppy disk and hard disk models that were compatible with the Lisa. MacWorks Plus consisted of some 23,000 lines of source code for the Lisa-dependent hardware interface and bootstrap code, plus an image of the 128K ROM that was licensed from Apple. It also included a standalone installer and a Control Panel that enabled a user to adjust certain Lisa specific features from inside the Mac OS user interface. {{Timeline of Lisa models

External links

Sigma Systems 7 MacWorks Plus II DeveloperMacWorks Plus: Making A Lisa Speak Macintosh – Call-A.P.P.L.E. (callapple.org)
Macintosh platform Macintosh platform emulators