============================================================================== [ THE KAY*FOG RBBS | Filename=CPM-CC22.ART | posted 07/05/86 | 171 lines 10k ] The CP/M Connection Originally published in by Computer Currents Ted Silveira 5720 Hollis Street (copyright and all rights reserved) Emeryville, CA 94608 March 11, 1986 EMULATING CP/M Several times in the last few months, I've mentioned CP/M emulators that allow you to run CP/M programs on an IBM PC or clone. I've now had a chance to play with one of these emulators, a package called Acceler8/16 from Intersecting Concepts. [What a CP/M Emulator Does] A CP/M emulator is a program that makes an MS-DOS computer imitate a CP/M computer, by creating CP/M environment within the memory space of the MS-DOS computer. When a CP/M program runs, it sees nothing amiss and chugs merrily away. In the background, meanwhile, the emulator is running madly about, intercepting the CP/M program's instructions to its fictional CP/M computer and translating them into instructions the real MS-DOS computer can handle. Software emulators are usually cheap but slow. Recently, however, software emulators have gotten a hardware boost from the NEC V20 chip, a pin-for-pin replacement for the 8088 chip that's the brain of most MS-DOS computers. The NEC V20 not only runs the same instructions that the 8088 does (and 10-20% more efficiently to boot) but also can run the instructions used by the older 8080 chip. And the 8080 just happens to be the chip for which CP/M was written (though almost all CP/M computers now use the Z80 chip with its extended instruction set, which causes some problems I'll mention later). When the NEC V20 chip is flipped into its "8080 mode," it can execute 8080 instructions directly, so the emulator software doesn't have to do nearly as much work. As a result, a CP/M emulator that takes advantage of this chip runs about 300% faster than a software-only emulator. [Acceler8/16] Intersecting Concept's Acceler8/16 package was one of the first of these software/hardware emulators, though there are now several others. The full package consists of Media Master (a disk conversion program), Accel (the emulator), and an NEC V20 chip to install in your MS-DOS computer. [Media Master] Media Master temporarily converts one or more of an MS-DOS computer's drives so that it can read a "foreign" disk, such as one from a Kaypro or Osborne CP/M computer. It can read and write a large number of formats, both single and double-sided, including all the common formats--Morrow, Kaypro, Osborne, Heath/Zenith, Televideo, Xerox, etc.--and some I've never heard of--Beehive Topper, Idea Bitelex, and Royal Alphatronic. It won't do Osborne or Xerox single-density, only double-density. Unlike some disk conversion programs, which convert a drive to a foreign format and then leave it converted while you run other programs, Media Master converts your drive only as long as Media Master itself is running. From the Media Master menu, you can get directories of any drive, erase files from any drive, type or print files, and of course copy files from one drive to another, all with one or more of your drives converted to a foreign format. But as soon as you exit Media Master, you're returned to your native format on all drives. That means you can't run the CP/M emulator, stick in a Kaypro disk, and run a CP/M program--you have to copy the program to an MS-DOS format disk. I tried out Media Master on several disk formats, and it handled them all, with one exception. I found that while Media Master handled single-sided Morrow CP/M disks without problems, on double-sided Morrow disks (formatted on my Morrow MD3), it sometimes reported the disk space used incorrectly (though the files and file sizes were correct). I also found that my Morrow MD3 refused to read disks formatted by Media Master in the Morrow format. I talked to Mark Graybill at Intersecting Concepts about this problem, and he quickly traced it to a bug in the Morrow MD3 format table, a bug that apparently exists only in the particular version I have (3.0) and not in earlier or later versions. The company's policy is to fix such bugs free (applause), so a new disk is on its way. Any of you who also have this problem should contact Intersecting Concepts. [Accel] Accel, the actual CP/M emulator program, comes in four versions. The first is a plain vanilla version. The other three emulate the video characteristics of a Kaypro, an Osborne, and a Heath/Zenith H19 terminal, respectively. This terminal emulation works well and lets you run CP/M programs without reinstalling them, if they originally were installed for the Kaypro, Osborne, or H19. When you run Accel, it creates a CP/M environment complete with the built-in commands like DIR and ERA. It also includes a few ZCPR-like enhancements such as automatic search of drive A for programs. The only noticeable difference from normal CP/M is that all your CP/M programs must be renamed using the filetype CPM instead of the usual COM (so MS- DOS won't confuse them with its own COM files). You can run Accel by itself, without the help of the V20 chip, but like all software-only emulators, it's so slow that it will drive you crazy. If you have the V20 chip installed, however, the performance isn't bad. While there's some argument about whether benchmark performance is slightly better or slightly worse than a typical Z80 computer, what I noticed most was the screen speed (the speed with which the computer can fill up the screen with text or whatever). The screen speed using the Kaypro terminal emulation is slower than that of my CP/M Kaypro. And the Kaypro itself is not a speed demon, being slower than my Morrow (with a Televideo 925 terminal running at 19,200 bits per second). I found the results good enough to be usable, but I did get tired of waiting for things to happen on the screen. Accel runs pretty much everything it claims to, which means everything that's written for generic CP/M and uses only the 8080 chip instruction set, but it does have a few limitations. As I mentioned earlier, most CP/M computers now use the Z80 chip, which has some extra instructions that the 8080 doesn't. Programs that use these Z80-only instructions won't run under Accel, but fortunately, most CP/M programs stick to the 8080 instructions (so they can run on as many CP/M computers as possible). Accel also won't run programs that use certain BDOS and BIOS calls, mostly ones that work intimately with the disk drive (BDOS functions 27 and 31, and BIOS functions 8 through 16). Programs that will run include DDT, ASM, dBase II, and the new OutThink thought processor from Kamasoft. Programs that won't run include SD, NSWP207, UNERASE, and DU (or any other disk editor). WordStar will also run under Accel, but if you have the Kaypro factory-installed CP/M WordStar, be prepared for some problems, since Kaypro modifies the program. So far I haven't been able to get this version to run. When I first tried running the Kaypro WordStar, the computer would load it and then immediately reboot, returning me to the A> prompt without doing anything. I then remembered that Kaypro modifies its versions of WordStar to program the cursor keys, so I dug into it with DDT and disabled the offending code (at locations INISUB, UNISUB, and MORPAT). When I tried this new version of WordStar, it loaded and went to its first menu just as it should, but then it refused to do anything except exit. It acted as if it couldn't find its two overlay files, WSOVLY1.OVR and WSMSGS.OVR, even though I verified that they were on the disk. I haven't yet figured out what this second problem is--more information next time (I hope). Overall, both Media Master and Accel do what they claim to. Except for the quirk with Morrows, Media Master seems a solid program, and while Accel (when combined with the NEC V20 chip) won't blind you with its speed, it is usable . . . and miles ahead of any software-only emulator. I do wish it were possible to use "foreign" disks directly while in the CP/M mode, but I can work around that. (I've heard that a similar program, RUNCPM from Micro Interfaces, does allow this, but I haven't seen it.) If you're interested in CP/M emulators--and you must be if you've hung around this long--you might also want to look for a copy of the February 1986 Computer Shopper, which has an article comparing half a dozen emulators. Acceler8/16 $99.95 Intersecting Concepts, Inc. 4573 Heatherglen Ct. Moorpark, CA 93021 805/529-5073 ------------------------------------------------------------------------------ Ted Silveira is a freelance writer and contributing editor to several computer-oriented publications. He appreciates suggestions or feedback and can be reached through the KAY*FOG RBBS (415)285-2687 and CompuServe (72135,1447) or by mail to 2756 Mattison Lane, Santa Cruz, CA 95065. ------------------------- End of CPM-CC22.ART Text -------------------------