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| A/ROSE | |
|---|---|
| Developer | Apple Computer |
| OS family | |
| Working state | Historic |
| Initial release | February 1988; 37 years ago (1988-02) |
| Supported platforms | Macintosh Coprocessor Platform forMacintosh (Motorola 68000) |
A/ROSE (Apple Real-time Operating System Environment) is a smallembedded operating system that runs onApple Computer's "Macintosh Coprocessor Platform", anexpansion card for theMacintosh.
The idea was to offer a single "overdesigned" hardware platform on which third-party vendors could build practically any product, reducing the otherwise heavy workload of developing aNuBus-basedexpansion card. However, the MCP cards were expensive, limiting the appeal of the concept. A/ROSE had very little use, apparently limited solely to Apple's own networking cards forserial I/O,Ethernet,Token Ring, andTwinax.[1]GreenSpring Computers developed the RM1260, which is an IndustryPack (IP) carrier card with a68000CPU running A/ROSE and is intended for thedata acquisition market.
A/ROSE and the MCP originated in August 1987 during the development of theMacintosh II. While working on various networking products for the new system, the developers realized that the existingclassic Mac OS would make any "serious" card difficult to create, due to largelatencies and the difficulty of writing complexdevice drivers. Their solution was to make an "intelligent" NuBus card that was essentially an entire computer on a card, containing its ownMotorola 68000 processor, working space in RAM mirrored in the main system, and its own basic operating system. The first version of the system was ready for use in February 1988.
A/ROSE was internally called MR-DOS (Multitasking Realtime Distributed Operating System), butMicrosoft (the developer ofMS-DOS) did not appreciate the name and put pressure on Apple to change it.[citation needed] Eric M. Trehus, a QA engineer on the Token Ring card running A/ROSE reportedly said "A/ROSE by any other name is still MR-DOS."[citation needed]
A/ROSE is infamous for itsesoteric purpose, which is generally not understood by Macend users, and for causing many Macemulators, such asBasilisk II, to produce a system error at boot time.
A/ROSE is very small at 28KB, with a 6 KBkernel. A/ROSE supportspre-emptive multitasking withround-robin scheduling of tasks, with a 110microsecondcontext switch time and only 20 microseconds of latency (guaranteed interrupt response time). The system's task is primarily to move data around and start and stop tasks on the cards, and the entireAPI contains only tencalls.
A/ROSE is amessage passing system, and the main calls made its programs areSend() andReceive(). Messages are short, including only 24 bytes of user data, and sentasynchronously. To find the appropriate endpoint, its name server allows the applications to bind their names to their task IDs, allowing them to move in the system and be found dynamically. The OS has several routines for finding, starting, and stopping tasks on other cards, one of which is a virtual card representing the host computer.
To coordinate communications and provide a mechanism for talking with the host's CPU, a cut-down copy of A/ROSE also runs inside the Mac OS in the form of asystem extension, or "INIT", known as "Prep". Device drivers for A/ROSE cards are INITs and started up automatically. After starting, they find the Prep stub and use the normal A/ROSE communications channel it provides to communicate with the cards.
For instance, the Apple TokenTalk NB card installs its driver as an INIT, and optionally installs the Prep stub, assuming it had not been installed before. On startup the driver finds the Prep stub and asks it to enumerate the TokenTalk cards installed in the machine, and optionally uploads code or settings to them. From that point on, Prep handles the communications with the card, handing off the results to the TokenTalk driver.
