MacWorks Plus
Encyclopedia
MacWorks Plus was a complete implementation (port
) of the Macintosh Plus
128K ROM on the Apple Lisa
and Macintosh XL
computer systems, and introduced in August 1988. It was developed for Sun Remarketing
of Cache Valley
, Utah
, under license from Apple Inc., 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
was System 3.2.
, which at the time was Apple's flagship product. This was a technically challenging goal because other than sharing the same Motorola 68000
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 Mac OS
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
in the original Macintosh ROM, and a hardware Memory Management Unit (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.
Porting
In computer science, porting is the process of adapting software so that an executable program can be created for a computing environment that is different from the one for which it was originally designed...
) of the Macintosh Plus
Macintosh Plus
The Macintosh Plus computer was 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$2599...
128K ROM on the Apple Lisa
Apple Lisa
The Apple Lisa—also known as the Lisa—is a :personal computer designed by Apple Computer, Inc. during the early 1980s....
and Macintosh XL
Macintosh XL
Macintosh XL was a modified version of the Apple Lisa personal computer made by Apple Computer, Inc. In the Macintosh XL configuration, the computer shipped with MacWorks XL, a Lisa program that allowed 64 K Macintosh ROM emulation...
computer systems, and introduced in August 1988. It was developed for Sun Remarketing
Sun Remarketing
Sun Remarketing was a retail company, located in Cache Valley, Utah, that specialized in reselling old Apple Computer software and hardware, including Apple II and Apple Macintosh parts such as motherboards and peripherals...
of Cache Valley
Cache Valley
The Cache Valley is an agricultural valley of northern Utah and southeast Idaho 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.-History:...
, Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, under license from Apple Inc., 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
System 6
System 6 is a graphical user interface-based operating system for Macintosh computers. It was released in 1988 by Apple Computer and was part of the Mac OS line of operating systems. System 6 was shipped with various Macintosh computers until it was succeeded by System 7 in 1991. The boxed...
. 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
System 6
System 6 is a graphical user interface-based operating system for Macintosh computers. It was released in 1988 by Apple Computer and was part of the Mac OS line of operating systems. System 6 was shipped with various Macintosh computers until it was succeeded by System 7 in 1991. The boxed...
with the Basic version, and introduced a Pro version to extend support to the maximum possible for any 68000 processor: System 7.5.5
System 7
System 7 is the name of a Macintosh operating system introduced in 1991.System 7 may also refer to:* System 7 , a British dance/ambient band* System 7 , 1991 album* IBM System/7, a 1970s computer system...
. Prior to MacWorks Plus, the maximum system supported by its predecessor MacWorks XL
MacWorks XL
MacWorks XL was an Apple Lisa software program that shipped with the Macintosh XL. It allowed 64K Apple Macintosh ROM emulation so the Macintosh XL could run Mac OS programs.-History:...
was System 3.2.
History
The design objective for MacWorks Plus was 100% compatibility with software that ran on the Macintosh PlusMacintosh Plus
The Macintosh Plus computer was 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$2599...
, which at the time was Apple's flagship product. This was a technically challenging goal because other than sharing the same Motorola 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
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 Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
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
Macintosh Toolbox
The Macintosh Toolbox is a set of application programming interfaces with a particular access mechanism. They implement many of the high-level features of the Mac OS. The Toolbox consists of a number of "managers," software components such as QuickDraw, responsible for drawing onscreen graphics,...
in the original Macintosh ROM, and a hardware Memory Management Unit (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.