CDC 6600 display character generation

Using all of those gates to do brute-force logic for character vector generation is pretty brilliant. Edison was truly a genius because he invented and sold the electric light so that people could stay up late at night to listen to his phonograph invention that he also sold. The electric lights also eliminated the risk of coal tar condensing on the phonograph cylinders from coal gas lights on the walls. Seymour Cray was a genius because he observed that the fastest possible circuit is a wire, and that if you use the same length of wire for each bit in a word in cables between stages in a computer that you want to go as fast as possible, all of the bits will arrive at the next stage at the same time. That was important for computers that took up entire rooms, with circuit boards and racks far enough apart that upwards of a dozen nanoseconds could elapse as bits passed from stage to stage. IBM "solved" this synchronization problem in the 6600's contemporary, the Model 3090 (Stretch), using delay lines to hold bits arriving on shorter cables until bits arriving on longer cables could catch up. The last thing you want in a supercomputer is a component that has the word "delay" in it, and by using equal-length wires for every bit in a word between stages, you also reduce parts count. That means that you reduce parts and assembly labor costs, replacement parts costs, power and cooling costs (a very important function, back then), system volume and weight (and therefore, structural costs), and the costs of troubleshooting labor needed to identify which parts have failed that didn't need to be there in the first place (or additional circuitry to identify where faults occurred, adding yet-more of all of the above expenses). At the time, CDC had 39 employees, including Seymour and the janitor, while IBM's engineering and technician head-count alone was upwards of 20,000. The 6600s were the fastest computers in the world for over six years, and would have held the record longer, except that CDC's own 7600s eclipsed them. He hired local women with experience doing mind-numbing, repetitive, but precision tasks like knitting and needlepoint, to wire the interconnects between boards on the Cray 1s and 2s. However, they could gossip about who was seeing whom around town to while away the hours, for which they were paid less than technicians, but more than for any other work women could get back then. I'll bet they made fewer mistakes than alternative employees would have, too. Seymour told them how important their work was to the nation's defense, and they were proud of it (many Crays were used on DoD projects for advances in pure science, as well as engineering). "Things should be as simple as possible, but no simpler." -- Albert Einstein (talking about scientific education, but not a bad idea, in general) On Wed, Jun 6, 2018 at 3:26 PM, Paul Koning <paulkoning at comcast.net> wrote: