This page is dedicated to the first MS-DOS coprocessor cards for the Macintosh, the Mac286 and its sibling the Mac86. I have created this page in response to the lack of information about these cards that is publicly available.
In 1987, Apple Computer released the first expandable Macintosh computers: the Macintosh SE and the Macintosh II. In those days, the gap between the worlds of the Mac and the IBM PC was much wider than it is today. To help bridge the gap, AST Research introduced a pair of MS-DOS coprocessor cards for the Mac. The Mac86 was an i8086-based card for the Mac SE, while the Mac286 was a higher performance i80286-based card for the Mac II.
In 1989, AST completed its exit from the Apple market and sold the rights and technologies for the cards to Orange Micro, a long-time player in the Apple marketplace. Orange Micro would go on to make a successful line of coprocessor cards based on the 80x86 processor family. By this writing (August 2001), Orange Micro had exited the coprocessor market to concentrate on USB and FireWire products.
In 1992, Orange Micro discontinued the Mac286 board. Support for the card was discontinued sometime later.
This page is divided into several sections:
There are three distinct versions of the Mac286 hardware:
Of the three versions, the AST appears to be the most common. Without knowing any sales figures, I can not surmise whether this is due to there being a greater number of them or to the more expandable Orange Micro cards being more sought after.
Details of the hardware are as follows:
The Mac286 software provides emulation of the following additional hardware:
If this all seems primitive, remember that this was 1989. Heatseekers could choose between systems running an Intel 80386-16 (20mhz versions were still in short supply) or an AMD or Harris 80286-20. The typical office was a mixture of standalone PCs, PC/XTs, and PC/ATs. The dominant office applications were Lotus 1-2-3, WordPerfect 4.2, Ashton Tate's dBase III, and Software Publishing's Harvard Graphics 2.3. (Microsoft Access was a communication program that most people were trying to forget.) The dominant OS was MS-DOS, including IBM's PC-DOS. Microsoft Windows 3.0 was still two years away and relatively few native applications ran under Windows/286 and Windows/386 (as Win 2.X was known). It was the last dance for DOS and the Mac286 was a respectable, if not cheap, date.
Finding a Mac286 board in 1998 is a largely "hit and miss" affair, requiring considerable determination and patience. Based on my own experiences, the three most likely places to find one are:
Figure on spending between $25-$30. For that price, you will likely get an AST Mac286 with a copy of the software (likely downloaded from here).
As is the case with most things in the PC world, the reasonable upgrade path for a Mac286 board is to replace it with a later Orange Micro card (386 or better). For those inveterate tinkerers/experimenters who want to see what can be done with the card, I present the following areas for consideration.
NOTE: The following are only suggestions based on upgrade strategies for a real PC. They may not be compatible with the Mac286 board and could potentially damage the board, your Mac, or both. As such, these suggestions are made without warranty and the author herewith disclaims any responsibility for damages that may occur.
Back in the days when an IBM PC/AT was a workhorse system, one of the best upgrades you could install was an 80287 math coprocessor. If your common application mix made use of floating point arithmetic, it was common to see speed improvements of several hundred percent.
On the Mac286, the 80287 chip is installed in the empty 40-pin socket next to the CPU chip. It must be rated for at least 6mhz operation.
The 80286 processor on the Mac286 is fitted in a PLC socket on the CPU card. In theory, it should be possible to replace the chip with an 80386SX or 80486SLC-based upgrade (such as the Make-It 486 product from Improve Technologies). This should give some increased performance.
The orientation of the processor and the spacing of the cards and the NUBUS slots may, however, make it difficult to install. Also, I do not know what, if any, timing problems may be introduced by the new CPU chip.
Unfortunately, the 286 upgrade chips have been discontinued for sometime and are only available on the surplus market. If someone wants to give/loan me one, however, I would be willing to try it and report back on the results.
The Mac286 board comes equipped with 1MB of non-parity memory. This comes in the form of 4 256Kx8 30-pin SIMMs. Of this 1MB, 640K is visible to MS-DOS. In theory, it should be possible to replace the 256K SIMMs with 1MB SIMMs, for a total of 4MB.
In practice, the ability to upgrade the memory depends on which version of the card you have.
All Orange Micro versions of the Mac286 were designed to support a 4MB RAM upgrade. Installing 4 1MB SIMMs will result in a system with 640K Real and 3008K Extended (3MB minus 64K) memory.
The AST version, unfortunately, is limited to 1MB of RAM. If you install 4 1MB SIMMs on an AST card, the power-on self test (POST) will only report 640K of memory and stop with a "Configuration Error- Run SETUP" message.
Background: The CMOS memory image for the emulated system is stored in a resource called "cmos" in the Mac286 executable. There are two images, one for a 1MB system and one for a 4MB system. It appears that the Mac286 executable saw the fact that 4MB of memory was installed and loaded the proper CMOS image. For some reason, however, the POST could not find the memory and stopped at 640K. Presumably, this is because of some address decoding hardware that is missing on the AST card.
The virtual C: drive of the Mac286 comes pre-installed with MS-DOS version 3.3. I have, however, successfully run newer versions of DOS including:
In all three cases, however, I was forced to sacrifice access to the Mac file system via the emulated D: drive. This was due to the inability of part of the disk redirector (dstep1.exe) to recognize and function with the alternative operating system. Using the SETVER command did not resolve the problem.
It may also be possible to install a small Unix-like operating system such as Minix or ELKS onto the virtual HD. I have not, however, attempted this yet, so I can not speak for the results.
Version 3.02 of the Mac286 software (the final version) is available here (MacBinaryII, 460K).
Version 2.1 of the Mac286 software (which seems to work better on some older Mac II's) is available here (MacBinaryII, 476K).
NOTE: You will need to turn off 32-bit addressing to run this software.
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