Programs Let MS-DOS Machines Take Advantage Of The 386 Chip

Intel’s 80386 chip holds a lot of promise for scientists working in all areas of computer-supported research. In addition to increasing memory capacity over its immediate predecessor, the Intel 80286, the 386 packs far more power. With it, for example, scientists will be able to run complicated molecular modeling or number-crunching programs on their desktop PCs. But it will be a while before that potential is realized in the IBM-compatible world since, for the full 386 power to be “unleashed,” an operating system more complex than even the latest version of MSDOS is necessary. This will come eventually in the form of an update to IBM’s OS/2, currently available only for 286-based machines. Does that mean that chemists who want to work with complicated molecular models or neurobiologists who want to design neural network simulation programs, can gain nothing from their spiffy new 386-based PS/2s, Compaqs, or other machines whose processing is still governed by the “old-fashioned” MS-DOS operating system? Do they have to just sit back and run their PCs as fast XTs until IBM releases its OS/2 for the 386? Not at all! Thanks to a couple of remarkable programs, at least some virtues of the 386 chip can be seized right away. Four Techniques Both packages—386 To The Max (386-Max) and QEMM/386 (for Quarterdeck Expanded Memory Manager) use four techniques to capitalize on the 386’s capabilities: remapping memory addresses; compensating for inadequate memory hardware; turning extended memory (XMS) into expanded memory (EMS); and filling unused memory by mapping extended memory. Let’s take them one by one. Remapping Memory Addresses: Both QEMM and 386-Max allow scientists to take advantage of the 386 machine’s ability to completely reassuring or remap. memory addresses. These programs can set up translation tables so that certain physical memory addresses are mapped or assigned to different logical memory addresses. For example, with either of the two new packages, the slow video read only memory (ROM) on EGA cards can be changed to fast random access memory (RAM) as follows:] QEMM or 386-Max copies the ROM into RAM and then maps the ROM area into an unused memory region, somewhere in extended memory. The copy now in RAM is mapped to the original ROM addresses. Thus, when a program thinks it is calling on graphics code in ROM (a molecular model, for instance), it is actually calling on code in the faster copy in RAM. Compensating For Less Than Optimal Memory Architecture: QEMM and 386-Max can compensate for inadequate memory architecture on 386 machines by working around limitations to the basic DOS 640K. For example, some early 80386 machines only supplied 512K for DOS and some remaining memory as extended memory. With QEMM and 386-Max, a scientist can map some of that extended memory into lower memory to fill up DOS’ 640K quota. By doing so, a scientist can load more memory resident programs, can load programs that require a minimum of 640K to run, and can run efficiently programs that require 512K or more. Turning Extended Memory Into Expanded Memory: Another critical use for 386-Max and QEMM is to change extended memory into expanded memory. By turning XMS into EMS, the scientist can use programs that make special use of EMS, like Lotus 1-2-3 or SideKick Plus, as well as run multitasking programs m memory space below 640K Filling Unused Memory Addresses: Finally, these programs will fill in unused memory addresses between 640K and one megabyte, an area DOS doesn’t know how to use, by mapping extended memory there. Then the scientist can load resident programs in that area. I have 110K of programs that I’d normally place in low memory (like the control part of my disk cache that I instead place in this upper memory saving lower memory for applications). There is one downside to these programs: Because of the lack of standards for the 80386, QEMM and 386-Max both run in a “virtual 8086 mode” as if they were working on the less powerful 8086 machines. As a result, scientists cannot simultaneously run one of these memory managers with any program that runs in 80386 mode. Thus, scientists already attached to 80386-based multitasking programs and 386-based virtual debuggers may not want to invest in a memory manager. Recommendations But for everyone I highly reeommend a memory manager. I would suggest QEMM for scientista using Desqview (the best-known multitasking package), also from Quarterdeck, since QEMM has links to undocumented parts of Desqview. On the other hand, 386-Max has special support for Omniview and for Windows/286. As a smaller company, I’ve found Qualitas a little more responsive to users. In either case, why continue running your 386 machine like a fast XT when you can take advantage of that power sitting on your desk right now? Barry Simon is IBM Professor of Mathematics and Theoretical Physic. at Caltech.

Programs Let MS-DOS Machines Take Advantage Of The 386 Chip

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Barry Simon

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December 1988

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