I was trying to get a DR11-W to talk between a rack-mounted VAX-11/750 and an Ungermann-Bass Ethernet box. I spent weeks on it and finally tracked it down to a house-built parallel cable that had a shared ground wire. We switched to a DEC cable that alternated signal and ground wires across the flat cable. Worked the first time.
wunder K6WRU Walter Underwood CM87wj http://observer.wunderwood.org/ (my blog) > On Jul 31, 2025, at 1:42 PM, Jack Brindle via Elecraft > <[email protected]> wrote: > > I was quite surprised during my time at Sun Microsystems that the address and > data buses on our Sparc Systems were not terminated. In fact there was no > consideration at all given to them being transmission lines, even though they > were running at a few GHz. The systems worked very well, with no problems. > These days high-speed buses in computers are serial. It turns out that > running a few hundred parallel lines that are the same electrical length (and > thus have the same propagation timing) is a very, very difficult problem to > solve. Much easier to have just a few serial lanes that carry the data at > super-high speeds. > > Sometimes we can overthink things when simple is what is really needed. Wayne > did a really good job with the K2… > > 73, > Jack, W6FB > > >> On Jul 31, 2025, at 2:47 PM, Fred Jensen via Elecraft >> <[email protected]> wrote: >> >> "It is amazing how we were able to build radios with only 2 sided PCBs for >> 50 ohm micro or strip lines." >> >> In the later 70's we took delivery of a Data General Nova 3 mini-computer >> that came with a FORTRAN compiler. The circuit boards were 15" square-ish, >> 2-layer. We quickly discovered that periodically but unpredictably, >> execution of the compiler would quit dead on a DO statement in the source. >> It just stopped. No other statement, only a DO and not all the time, but if >> it stopped, it did so on every recompile of that source. >> <mailto:[email protected]> >> >> After several DG visits they finally believed us and showed up with their >> Guru in flip-flops, ragged board shorts, a torn T-shirt, and fairly long-ish >> uncombed hair. He said almost nothing and the other 3 DG's [in "computer >> expert" business attire] were very attentive to him. >> <mailto:[email protected]> >> >> He spent most of the morning with the 'scope making notes in a beat-up >> notebook in indecipherable script and diagrams. Finally muttered something >> to his minions who raced to get him an Xacto knife, some very light >> insulated wire, and the soldering station. He cut both ends of several >> parallel traces and replaced them with twisted pair jumpers. The compiler >> never stalled on a DO statement again. >> >> Problem likely would never have occurred had the board had a 3rd ground >> layer between the two outer ones but they they had yet to be invented. >> >> 73, >> >> Fred ["Skip"] K6DGW >> Sparks NV DM09dn >> Washoe County >> >> >> >> -- >> This email has been checked for viruses by AVG antivirus software. >> www.avg.com >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
