Hi Everyone, Anyone that knows me knows I love relating a story when I can about the little details that still make me laugh and occasionally cry these many years later. CBM's engineering department was relatively small, it fluctuated between 20-30 people INCLUCING the technicians, engineers programmers, IC designers, IC layout people and PCB designers. Needless to say since we all pretty much fit on a volleyball court at the same time we knew each other real well and the best stories assume you knew how so-and-so acted when drunk, etc. So Gerrit left an opening for the keyboard story on the TED/264/Plus4, that really has the back-story of when I, being the 23 year old unschooled long haired kid finally took ownership of the TED project as opposed to being just it's custodian. When I got to CBM as related in the commodore.ca article, I was supposed to be a programmer for the disk drives, and in Bagnals book I was supposed to be a technician, good thing I didn’t know that at the time. These were the days when CBM would add someone to the ranks without knowing where they fit in, they were just on a constant hunt for talent in what we call the 202 area of Philadelphia. I ended up the lead on the project because the guy that was lead was leaving, he didn’t really like TED or understand it, (he was afraid of the intricacies of the chip) and he was the third or forth engineer to have cycled through on the project. This was the tail end of a mini-exodus of engineers that weren’t quite suited to CBM style designing, they could probably have designed test gear for Boeing and been right at home but at CBM you need to move fast and live with the fact that the products will never be perfect, in some cases fairly flawed. I found timing charts where the original “TED” engineer had set out to prove that the TED timings didn’t work, he also had a set of "poo poo" docs on the C64, Vic and PET, even though they were in production and selling he claimed they didn’t work (okay he was right but for the wrong reasons. >:) ) This guy did things like add a 22 ns delay for the database capacitance which is unrealistic. The good news is by studying his work I developed my own style of timing analysis for adding min/max timings and reference points, being completely unschooled I had to teach myself everything that was common sense to a grad, such as Boolean tables, etc. This 2nd-to-last TED engineer had a nickname in my group, we called him "shooting star" since he was obviously so much better than us, his time at CBM was a mere waystation on his astronomic trip that was to be his career. I would trip over his work again as he had "designed" the CPM cartridge for the C64, I still have in my files the schematic I found in his stuff a couple of years later, he clearly had lifted the design from the CPM card for the Apple. I got put on TED because I was the only guy left that understood that they were “sharing” the bus with video and that they would ”steal” more time for the refresh, etc etc. I spent my spare time standing next to the prototype, so I became associated with it. When I was officially put in charge of the TED the first thing I did was throw the prototype in the trash pile as it was based on a VIC chip and had nothing to do with TED… they were just killing time by wiring up a smaller C64 to the point where people kept stealing the R7 Vic chip out of the socket, they would even insert their old R5 sometimes! I fought this tendency by ordering a whole tube of R7’s and put them on the desk with a sign that said take one. After everyone got the personal C64’s updated the Vic chip thefts stopped. So there was ONE RULE when I got the Ted project, it has to have xxx number of chips (I think it was nine chip) and no more, signed Jack Tramiel. Well the TED’s reset circuit consisted of an RC circuit and a 7407. I proved it wouldn’t work but I didn’t think about what this really meant as to who had designed the computer (the answer was no-one had designed the computer at that point) It was an easy argument to make that the computer would fail en masse, we HAD to add a chip for reset, didn’t matter which chip, we simply could not do it with a transistor or a 7407 gate. (yes I tried feedback to create hysteresis ) The answer came back from the mountain that it was okay to add a chip. I remember that people were stunned that I had challenged this (some thought I would be fired) and won. But here’s where I screwed up, I missed the opportunity to understand why the reset circuit sucked and consequently why the un-buffered data lines scanned the keyboard and ultimately the joystick. The problem was that the TED design was set by the chip and consequently the chip designers. They did an amazing job for a single chip approach, especially for back then, again it was a workmachine specification for the cheapest computer we could build, not a game machine, specifically DON’T compete with the C64. The chip designers were Bruce Ahearns, Dave DiOrio and Eric “Chow Yan” Yang, and they nailed it in my book. (they had no electrical rule checking, the chip was hand laid out and hand checked using small rulers and pen plots) To a chip designer it would make perfect economic sense to scan the concept of a keyboard with the datalines…. Perfect sense. I missed this fact every time I stared at the schematic… _every_ time and I looked at it a hundred times. I was looking at the schematic from the eyes of someone that cant make changes or add chips or impact the design other than a few support items like reset circuits and some RFI suppression, even the connectors were already designed by the case designer Ira Velisnsky who has since passed away. We never tested the joystick port until the new custom joystick arrived hand carried by Ira. (We didn’t even have DIN connectors in engineering at the time) And boom, plugging in the joystick caused video data corruption. I looked at it right away and figured that if this was real data corruption then it should also crash the processor. I held the joystick up to the monitor and sure enough it locked up. Within minutes a crowd formed including my boss. I looked at the schematics and finally realized that indeed the DATA lines are being drug all over the keyboard and down a 4 ft cable and I laughed. I knew all the ways that was bad, the ringing and RFI emission, the susceptibility to interference (w/o joystick) and plain and simple you DON’T do that to data lines. It pissed my boss off that I laughed, I told him that I was laughing at my own oversite, I had after all walked around with this schematic for many weeks. He was not amused. He said in so many words, “well if you don’t fix it right away your fired”. It pissed him off more when I was still grinning and he did his version of storming out of the lab. Knowing him he was calculating who to replace me with. So once I finally “saw” the dataline problem I knew I didn’t want a hard TTL part to isolate the lines, hard driven lines are RFI/FCC nightmares, especially since they would be above the metal keyboard plate, not below/inside. TTL also doesn’t like to be shorted out, even via capacitive loads. I remembered seeing that MOS had a single port I/O and in my mind this was perfect, it was ssssllloooowww on the output side (I/O speed instead of databus), It was NMOS which was more forgiving for RFI and shorts AND it was made by MOS meaning we could control how many are available (there was an LS shortage at that time that plagued pipleines for a couple of years). In less than two hours the tech (amazing techs) had “dead bugged” the 6529 to the underside of the board and also made me up a special joystick cable. My boss, Joe, walked in and I was standing there playing a video game, 10 years ago I could remember which game, I have since forgotten. I didn’t say anything, I wasn’t afraid, I was stone faced. He thought I hadn’t even started to fix the problem and raised his voice. I just pointed at the monitor. He got more pissed, I pointed again. Finally with that grin he hated I showed him that I had taken the cover off the monitor and wrapped a 20’ joystick cable around the picture tube, right on top of the yoke which looked scary to the unaccustomed (I had been a TV repairman when I was age 16-19). I wasn’t playing a game so much as proving that no longer were we susceptible to casual joystick, I had put 20’ right in the highvoltage flyback section of what was basically a TV. He turned and walked out, total cost to fix was something like $0.24USD per unit. More importantly though was I took ownership of TED that day, I HAD missed this very serious flaw because I didn’t question the design and the background of the origins of the design. That’s what I had been laughing about was I had understood that I now needed to do this. From there we did do some interesting things that the chip guys wouldn’t have known like creating a 1/4th duty cycle Phi2 so we could attach chips like the 6551 UART. (Actually we created a Phi0 so we would have data hold time) The end of the story was that I went to a CES show and woman pulled me into her booth to show me the educational software she had written for the C64. I remember her display had nasty lines in it, she didn’t yet have access to the R7 chips. She told me how she was a small business and how money was tight and then looked directly at me and told me that CBM had screwed her by not being compatible with what had taken her a year to write. When I got back from CES I wrote a memo, misspellings and all (we got our spellchecker later that year in the form of a VAX) entitled “Yes Virginia, there is compatibility”. That memo in a way, laid the foundation for adding a C64 mode to our next/last 8 bit machine, not so much to compete or doublesell but to support the developers that had supported us. Simply put that woman’s software would work on the next CBM machine, she could go back to worrying about the other things a small business person does. Bil Message was sent through the cbm-hackers mailing listReceived on 2011-08-20 17:00:13
Archive generated by hypermail 2.2.0.