Backing Up an M100 Chipmunk System Copyright [12/7/90] Lincoln Baxter,2nd After a career in Applied Physics at the Woods Hole Oceanographic Institution in which I participated in the introduction of computers to Oceanographic research and word processing to technical writing, I was facing retirement. I desperately wanted a computer of my own so that I could continue to practice my programming and writing skills. Then in 1983 I saw the M100. Wow!! Portable; small but powerful; lots of different ports; a real typewriter keyboard; and graphics too. If I'd only had this years ago! Then came Portable 100, the Chipmunk, the M100SIG, and the Boston Computer Society. I found that this little machine had possibilities grander than I had thought possible. It really fits the way I like to work. I had learned Fortran on the job. Now I learned Basic and Assembly. The programmers who designed the ROM in this machine had designed in flexibility! With RAM Hooks, if you didn't like some detail of a "canned" program, you could change it. Then came the T102 and the M100 was discontinued. Would my machine last? Would the new machine live up to the promise? The news was not encouraging. It seemed that the T102 was not compatible with the Chipmunk which I had come to depend on. Sadly, there would be no new Chipmunks. Would my Chipmunk last? Horrors! It began to fail. Would I be able to fix it? Yes I could! The problems were only with the ribbon cable and the battery. More about this later. Let's not get into the details before the general topic is fully introduced (see CHPSYS.EX3), but this started me thinking about greater development of my own support and, if the maintenance should ever become too difficult, about compatible transitions to another system. I hoped that I wouldn't have to replace the system. Why give up what is in many ways the best disk drive ever for working with files. Rather, I'd like to extend it by using the M100 & Chipmunk at home where it's less vulnerable and get a T102 and TDD2 for portable work, backup of the system, and keeping up with what other people are now using. Chipmunks forever! <> Also, it can't hurt to learn where my Chipmunk experience can help in organizing the newer T102 & TDD2 which I wanted for system extension. The principle of redundancy is involved in the equipment inventory of a completely backed up system. One would like to be able to continue to work as efficiently as possible despite the loss of any one item. I have two almost compatible computers, i.e. an M100 and a T102. I have two disk drives, i.e. a Chipmunk and a TDD2, both compatible with the M100, but with incompatible disk formats. I have a standard cassette drive and a microcassette drive. I will have some option ROMs and extRAM. There is considerable redundancy here, but critical files must be duplicated in the various magnetic media. See Part II [CHPSYS.EX1] Redundancy would be increased if the T102 could also access the chipmunk directly. Why can't it? Checking my old issues of Portable 100 I found that the firmware differences of the M100 and T102 computers had been discussed by Carl Oppedahl, "Weighing the Differences" [Portable 100, August 1987]. He concluded that there are a few small but possibly important differences in the firmware. One of his remarks caught my eye: <<"One Model 100 routine at 7304 that I could see no use for (it looked like a routine for a system-bus disk drive) has been gutted in the 102 to make room for the PRINTUSING patch and the telecommunications patch.">> What an interesting clue!! I think that this could be a reason, more critical than the difference in the the system bus hardware, for the T102 incompatibility with the Chipmunk. Hardware adapters are much easier to "hack" than firmware patches. However, there is hope... It looks to me as if with an adapter between the Chipmunk interface and the bus and a short driver program in RAM, option ROM, or better yet extRAM, the T102 could work with the Chipmunk. It's an interesting possibility. Since there will be no new Chipmunks it's not too practical commercially, but I may think about it later. For an excellent review of extRAM, see "The Many Personalities of extRAM" by Stan Wong [Portable 100, November 1990] Otherwise, the T102 seems to be better than the M100, slightly more rugged, slightly more portable, and some minor bugs in the firmware have been patched. Switching back and forth between M100 and T102 takes a little getting used to because of the different arrangement of the cursor arrows. I've begun practicing the [CTRL] E S D X moves etc. which are compatible between the machines and even intuitive if you think about where these keys are on the keyboard. Unfortunately they only work in TEXT and the BASIC editor. For some things you still have to use the arrow keys. The drives may be compared as follows: My original M100 system with the Chipmunk drive, which connects to the main bus on the M100, has the more versatile disk operating system with 370K bytes, random access to disk files, multiple directories and subdirectories, menu selection by cursor in the directories, faster access, and most of my files are on it. <>, but if your primary interest is preserving your files while switching systems, keep reading...I'll get to it later. (See CHPSYS.EX1) Though I'm fond of the Chipmunk, it is not what most people are using now; so I need to also have TDD capability. The Chipmunk has some other deficits: It has a fragile ribbon connector, is slightly less portable than the TDD, works only with the M100, was not designed or manufactured or supported by Tandy, is no longer manufactured, and is not replaceable. Because CDOS needs a fixed place in high memory it conflicts with some other programs; however CDOS is very easy to remove and load which mitigates this problem somewhat. The Tandy portable disk drive (model 2), TDD2, connects to the serial port, has a maximum capacity of 200K bytes on each disk. With its standard DOS called FLOPPY, it has only two directories and no subdirectories, no random access within a file, and can hold a maximum of 40 files in each directory. The files are selected by typing their names not by cursor. Some of these inconveniences might be eased with a better disk operating system, but I've been told that none that has been developed so far beats or equals the convenience of Chipmunk CDOS. The TDD2 is supplied with an operating system called FLOPPY which is a machine language program with some unusual characteristics. The loading procedure moves MAXRAM and HIMEM down to 60000 and the bulk of FLOPPY resides between 60000 and 62959. A 37 byte section stored as a machine language program on the menu but without the .CO extension, when selected by cursor, overlays the section from 62701 to 62738 and begins execution. The only proper way to remove FLOPPY and recover the normal MAXRAM value of 62960 is to run a short program called FREMEM.BA. Killing FLOPPY with the simple KILL command will leave you with no simple way to load it again or to recover the memory. To one who is used to normal machine language programs, all this seem unnecessarily complicated, unfriendly, and wasteful of memory. Other commercial operating systems for the TDD have been reviewed by Thomas L. Quindry in the October 1987 issue of Portable 100. Although its software support leaves much to be desired, the TDD2, considered as a portable drive, has several important advantages over the Chipmunk. It is smaller and lighter and its connection to the computer is more rugged. The TDD2 can be used either with an M100 or a T102 or with "LAPDOS" programs and cables that are available on the serial ports of either a MacIntosh or an IBM PC. It is still in production and costs less than half of what the Chipmunk cost. I have confirmed by test that the TDD2 works on the serial port of an unaltered early M100 like mine. Though this was not true of the early Tandy drive, the TDD model 1. Some people I know had to pay to have the impedance of the serial ports of their M100s altered to make them compatible with the model 1 TDD. This is one reason why I waited so long to add a TDD to my inventory. When I finally did, it was the TDD2, which I was pleased to learn would work with my M100 as well as the T102. Tony Anderson has pointed out to me that there is a DOS, developed by J.K. Heilman and Phil Wheeler, available from a file called DSKMGR.REL in Library 9 of the M100SIG on CompuServe that has the major advantage over FLOPPY of being relocatable which makes it compatible with other machine language programs including CDOS; so that a Chipmunk and a Tandy disk drive can be simultaneously operational and connected to the same M100. It even takes a little less memory than FLOPPY. Though developed for the earlier Tandy drive, it will work on the TDD2. However, it limits the capacity of a disk to 40 files, though 200k bytes are still available if the files add up to that much. DSKMGR.REL is a relocating loader in BASIC that creates a normal relatively friendly machine language program called DSKMGR.CO in file storage space. It has some very nice features which I will describe in the next section: [See CHPSYS.EX1, DSKMGR.DOC, & DSKMGR.DOR] <<>> /EX