On Jan 3, 2009, at 1:11 PM, Kent A. Reed wrote: > Gentle persons: > > I love these stories! > > I'm sorry, Gene, that you had such a bad experience. I can only > protest > that a PDP11/23 wasn't a *real* PDP11. It came out nearly a decade > after > the 11/20, had an LSI-based CPU instead of a boatload of M-series > logic, > used the Q-bus instead of the Unibus, and (the most telling point for > me) didn't have a *real* front panel. All this is just > rationalization, > of course. The truth is, you had to deal with a lemon at a time > when DEC > was already beginning to reel from competition and market conditions. > > I (technically my advisor, since it was his grant money, but it was my > lab partner and I who made the case and wrote the requisition) took > possession of the third PDP11 sold out of DEC's Chicago office. As > affordable as it was, it was so expensive compared to our research > budget that we had to buy the CPU, ASR33 teletype, and power supply > out > of one grant, the 4(yes, 4!)-Kiloword core memory module out of > another, > and the high-speed paper tape reader/punch and relay rack out of a > third. The system pictured on the home page http://hampage.hu/pdp-11/ > might as well have have been my system. > > The model line was so new that my escutcheon plate said "PDP11" and > not > "PDP11/20" as it did on later machines. It was so early in the > production cycle that I got documentation in the form of a set of > E-sized drawings red-lined with the ECOs installed during > manufacturing > and a bunch of prepublication drafts of manuals. Of course, all those > last-minute ECOs meant my backplane was chock full of colorful > wire-wrapped patches. With the exception of inevitable core-memory > issues (what minicomputer maker didn't have to run core-memory > tests all > the time?), the only real problems I ever had over the years were > inevitably the result of forgetting to observe proper Unibus etiquette > or screwing up my wire wrapping. > > When I complained about the lack of software documentation, the DEC > Field Service Engineer surreptitiously passed me a number of source- > code > distributions which I cheerfully pored through at night while my > experiments were running. It didn't take me long to discover that some > of the early software was actually PDP8 software mangled so a PDP11 > could interpret it, albeit slowly (not nothing did the PDP11 > instruction > set include the EMT, or emulate trap, instruction). I was the best of > friends with the Chicago office after I showed them my version of > BASIC-11 running 4 times faster than theirs because I had replaced the > emulated instructions with native code. I didn't do it for them. Real > men wrote only in assembler or directly in machine code. I had to make > BASIC work well because my advisor was hopeless with anything else and > he had some experiments of his own to run. > > In defense of my taking up bandwidth on the EMC mailing list, the > reason > we bought this PDP11 was to control and monitor a very large and > complicated experimental apparatus. Like a fly-by-wire aircraft, this > system would have crashed and burned if it weren't for computer-based > real*-time command, control, data acquisition, and processing. > > *I say "real" time, but keep in mind this was the early 1970s. I wrote > my software and meticulously counted cycles before RSX11M or its > country-cousin RT11 were available. Later, I got to spend some time > debugging an RSX11M program as a favor to a medical researcher at the > same university. Yikes. > > > Regards, > Kent > > Hi Kent,
Your point is well taken that the /23 and /03 were not REAL 11's. However they did have most of the instruction set and the code was straight forward and it worked. My /03 did have a simplified front panel. How else were you going to boot the machine? The code we used for the AA was written in assembly without the use of Macro-11. All hand-coded and toggled into the core memory including the FP routines. I didn't do it. One of my chemists did. Really bright guy. Never did diagnostics; the machine just ran for 10 years or so. We finally replaced it with a Varian AA and PC control. It wasn't as nice as the 11 but we needed to to do something off-the- shelf before I retired. Somewhere around here I have a 16Kword core module off an 11/40. One of my old Kennedy disk drives( 45 Mb) resides in my wife's library to show kids what technology used to be like. It has dual platters about 11" in dia and everything is so big you can see it. Plexiglas cover reveals all. I must say the 100 KHz 16 bit parallel cards were nice for slurping in data. Anyone really remember how many interrupts an 11 really had. I'm thinking 256 but haven't found the book to confirm that. Aren't war stories fun. Dave > ---------------------------------------------------------------------- > -------- > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
