On Wed, May 6, 2026 at 6:48 AM John R. Hogerhuis <[email protected]> wrote:
> The Covington map is from the CompuServe SIG archive. I assume he was > just a guy that disassembled/reverse engineered the ROM. It was a common > thing for hobbyists to do when they got a new microcomputer. > John, it took me a while to figure it out, but it seems the "Covington Map" on bitchin100's wiki <https://bitchin100.com/wiki/index.php?title=Model_100_System_Map_Part_7_(F5F4-FFEC)> has been altered with incorrect information. FF8D is definitely SERMASK, the serial mask as Peter described, not the "RS232 parity control byte". All other copies of Covington's System Map that I could find did not include that error. The Living M100SIG <https://github.com/LivingM100SIG/Living_M100SIG/blob/main/M100SIG/> has Robert Covington's M100 RAM map in a file called Lib-08-TECH-PROGRAMMING/100RAM.RDC <https://github.com/LivingM100SIG/Living_M100SIG/blob/main/M100SIG/Lib-08-TECH-PROGRAMMING/100RAM.RDC>. The file's timestamp is 07/31/88 (according to the 100ROM.ARC archive) and the revision date written at the top of the text is "09/30/85". Club100 <https://www.club100.org/library/libref.html>'s library reference page has a copy of the same file, renamed to rcmap7.100 <https://ftp.whtech.com/club100/ref/rcmap7.100>. (Side note: Although it has the same date of "09/30/85" written in it, the Club100 version contains a few typos. The other rcmap files on Club100 have similar minor deficiencies.) In Club100's "user uploads" there are two references to a system map, one of them is merely a text file with a dead link <https://www.club100.org/memfiles/index.php?action=view&filename=Mod100_System_MAP.txt&directory=Don%20Fox> and the other is a mushed together version <https://www.club100.org/memfiles/index.php?&direction=0&order=nom&directory=Mike%20Nugent> of all the Covington map files with very minor changes, mostly reformatting paragraphs to make it use less paper when printed. (Thank goodness for wdiff!) On Wed, May 6, 2026, 1:05 AM Peter Noeth <[email protected]> wrote: > I have seen the notation in the "Covington ROM Map", and I believe this > is where Ken got the same notation in his ROM listing (in his personal > library on the Club100 page). But it doesn't seem that Robert Covington > ever wrote a book on the Model 100. For such a detailed ROM listing, I > would have expected that he would have. He must have been involved in > accessories for the Model 100 in some capacity. > A reasonable question given that the most durable artifacts we have now are books. I researched it a bit and here's what I found. The M100 appears to have had a large and thriving community which shared their knowledge using the technology of the time: Newsletters, magazines, BBSes, and CompuServe. Digital documents were newborn then and not all of them made the transition to our modern Internet. We have no way of knowing how many "incunabula" may have been lost. Some of the most important documents are preserved in the Living M100SIG, but unfortunately that archive is not yet easily usable or discoverable. (Personally, I search the M100SIG by using `rgrep` on a local git repository.) Robert Covington was a technical writer and did publish quite a bit, but if he wrote a book, I cannot find it. Portable Computing Magazine published a series of his articles entitled "A Portable Machine" on machine language programming for the Model 100. We know this to be the case because they are referred to in the July 1985 issue of PCM which has an index <https://archive.org/details/PCM-Magazine/1985-07_v3n1/page/58/mode/1up?q=covington> of the previous two years, however the issues themselves are (for the moment) lost works: Covington, Robert D. “The portable machine - part 1. " (1984, December) p. 34 —Machine language tutorial. Covington, Robert D. “The portable machine - part 2. " (1985, January) p. 38 Covington, Robert D. “The portable machine - part 3. " (1985, March) p. 25 Covington, Robert D. "The portable machine - part 4. ” (1985, April) p. 31 Covington, Robert D. “The portable machine - part 5. ” (1985, June) p. 31 —Tutorial about the Model 100 display memory map. The July 1985 issue also contains an excellent tutorial by Covington <https://archive.org/details/PortableComputingMagazineJul1985/page/n49/mode/1up> on how the Model 100 ROM handles keyboard input. In the article he mentions that the ROM subroutines are listed in his "Great Memory Map", which sounds to me like the document we now refer to as the "Covington ROM Map". The "author bio" mentioned that Covington had just finished writing a book on Model 100 assembly language. I'm guessing that the series he had just published in PCM were that chapters of his book and his famous Memory Map was meant to be supplemental material. Did his book ever get printed? I don't know. One would think he'd have advertised it in PCM if he had, but I see nothing like that. It's quite possible that by 1985 he couldn't find publishers willing to bite on a book aimed at developers for a rapidly shrinking market. Over a year beforehand, in May 1984, Portable Computing Magazine had broadened its focus from solely the Model 100 to include the DOS based Tandy 2000 and Robert Covington had started publishing a second series in PCM, "Subroutine City", exploring the intricacies of MS-DOS and the BIOS. A year later, in July of 1986, PCM's anniversary index of articles for the entire year shows only one entry under the "Portables" heading: Covington, Robert D. “The portable machine - part 6.” (1985, July) p. 50 — Machine language hints. That article had ended with Covington saying, > *“So far I have discussed two of the three most used devices in the Model > 100: the display and the keyboard. Next month, I'll discuss the RS-232/ > Modem and its ROM routines.”* However, the next month, August 1985, only "Subroutine City" for the Tandy 2000 was published in PCM and Covington's promised Model 100 content never saw the light of day. That is too bad, particularly because the RS232 ROM routines have some hairy bits that Covington would have been able to explain in his clear writing style. What happened such that the series got axed abruptly? I cannot find anything mentioning it. I hope someday we do find that he published a book, or at least made it available somehow, and that it is merely obscure, like the other later Model 100 writings, such as the books by Tony Anderson <https://archive.org/details/ProgrammingTipsPeeksAndPokesForTheTandyPortableComputers/mode/2up> and Mo Budlong <https://archive.org/details/secrets-of-rom-revealed/page/n5/mode/1up>. However, both of those authors acknowledge Covington's System Map file but make no mention of any book. Tony B. Anderson described the Covington ROM Map in his 1989 "Programming Tips <https://archive.org/details/ProgrammingTipsPeeksAndPokesForTheTandyPortableComputers/>" book like so, > “…the most complete single source was a complete map of the Model 100, > developed by Robert Covington, and which is available in library 8 of > CompuServe's Model 100 Forum. The files are named 100ROM.RC0 through > 100ROM.RC6 (seven files), and 100RAM.RDC, along with the various 100 to 200 > conversion lists provided by other forum members. Address conversion tables > have been published in various support magazines; the most complete was in > the May 1986 issue of Portable 100 magazine.” My guess is that when the book deal fell through, Covington didn't want all of his hard work to be for nothing and so he released the map to the community at large. —b9
