Tom Thompson
Apple has developed a board that offers the ultimate oxymoron of software and hardware: a Mac running DOS programs. This feat is accomplished by placing a 25-MHz 486SX processor, a Chips & Technologies BIOS, a VGA chip set, and some of Apple's custom ASICs (application-specific ICs) on a 68040 Processor Direct Slot plug-in board. The whole affair is dropped into a competitively priced Quadra 610, offering the best of both worlds on one system.
The DOS card can have up to 32 MB of RAM on it, or it can share memory on the Mac's main logic board. At boot time, the board is scanned for RAM. If none is found, a user-determined amount of RAM on the main logic board is dedicated to the DOS environment. Hardware transceivers in a custom ASIC on the DOS card handle the endian byte-swapping require
d by the different processor architectures. A memory controller in this ASIC functions to keep the address spaces of the two environments separate. Also, the Mac's SuperDrive is mapped as A by the system. The MSCDEX extension is provided so that, on a Quadra with a built-in CD-ROM drive, DOS can access DOS CD-ROMs.
The PDS board operates independently of the Mac so that DOS/Windows applications can run concurrently with the Mac OS. However, Apple has taken its integration skills to fuse the two systems into one easy-to-use whole. For example, selecting a printer via the Mac Chooser automatically selects the same printer for the DOS environment. DOS print commands are intercepted by the Mac OS and routed to the selected printer. For example, say you have a Hewlett-Packard printer connected to your Mac. You select the HP printer driver from the Chooser. Under DOS, you print an HPGL (Hewlett-Packard Graphics Language) graphic. The HPGL commands are redirected to the HP driver, which sends them to the prin
ter. Running CorelDraw under Windows? No problem: Select a PostScript printer from the Chooser, switch back to CorelDraw, and print. For serial work, you can assign COM1 to, say, the Mac's modem port and COM2 to its printer port.
Switching between the Mac and DOS environments is easy. With a single monitor on the Mac, you press a user-selectable hot-key sequence, which toggles you from the Mac Desktop to a DOS screen. Pressing the same key sequence again swaps you back. If the Mac has two monitors, you can pick which monitor shows the Mac Desktop, while the other displays the DOS/Windows environment. Support for 14- and 16-inch VGA and Super VGA monitors is provided.
DOS files are maintained inside a container file that has the structure and organization of a DOS hard drive (a trick pioneered by Insignia Solutions' PC emulator). However, Apple lets you "mount" this file as a Mac volume that you can double-click on to open and examine DOS files and subdirectories (i.e., folders). DOS file extensi
ons can be mapped to the appropriate Mac applications, such as .XLS to Microsoft Excel and .DOC to Microsoft Word. With the file-extension mapping in place, double-clicking on a DOS file launches the corresponding Mac application. (Remember that many of today's cross-platform applications use the same file format, so this little trick works transparently to the user.) Cutting and pasting between Windows and Mac applications is supported.
You can configure the system to start DOS when the Mac boots or on user demand. When you shut the Mac down, the Mac OS checks to see if the DOS environment is active and will give you a warning to shut down DOS before proceeding. A single Control Panel lets you set up the DOS environment (e.g., its memory size and serial-port mapping). Not supported now are NetWare operations and Sound Blaster I/O.
Apple sees several target audiences for this product. First, the home office, where multiple users have different platform needs (e.g., the kids using Macs at school,
the parents using DOS at the office). Second, the small office, where folks don't have an expert to maintain their systems, and they don't care to wrestle with the technology. At the same time, these folks might need to run several vertical DOS applications. Finally, for training and education, where tight budgets require the most bang for the buck.
The board will cost $500 without memory. MS-DOS 6.2 will be provided, along with utilities like Double Space. A complete Quadra 610 with a keyboard, a 14-inch monitor, 8 MB of RAM, a 160-MB hard drive, built-in Ethernet, and a DOS card should cost about $2000. Resellers might bundle Windows with the system. Ironically, the ability to run DOS or Windows applications on the Mac may be the ultimate Trojan horse that garners the Mac market share.
Illustration: Apple's board handles the endian byte-swapping needed in the combined Intel/Motorola architecture.
Apple Provides PC on a Mac
