HELLER%dgatum5p.earn@NSS.CS.UCL.AC.UK (10/27/88)
Date: 26-OCT-1988 17:14:44.12 >From: HELLER AT DGATUM5P To: @TRANSPUTER,HELLER Subj: b004 at 20Mbit/s Comments: From: Patrick Van Renterghem, State University of Ghent References: > The Transputer Lab, Grotesteenweg Noord 2, +32 91 22 57 55 Keywords: > B-9710 Ghent-Zwijnaarde, Belgium, Europe. Fax: +32 91 22 85 9 Original-Sender: transputer-request@edu.cornell.tn.tcgould Hello folks, I would like to integrate our B004 in a T800 network where we use 20 Mbit/s links. Is there anyone out there who knows how I can run the B004 links at 20 Mbit ? I suppose the LinknSpecial pins are soldered to ground ? Okay, I could put 2 C011's across the links to do speed conversion, but I am looking for a more cost-effective solution ! Patrick Subject: running a B004 at 20%Mbit/s To: Patrick Hello Patrick, we have had the same problem and it's even more complicated than you think now: To put things on a line: a) It's true: the LinknSpecial pins are soldered to ground. To circumvate this, we put the T414 on two extra sockets. The lower of them (the one which actually plugs in the B004) with LinknSpecial pins removed to cut connection to ground. The upper (the one which actually holds the T414) allows now to make the desired connections without soldering directly on the T414. b) The complicated part is comming right now: on our INMOS board the T414 wasn't driven with the normal 5%MHz clock, but instead with 25%MHz directly out of the X-TAL oscillator. This is possible due to some undocumentated feature of the T414: pin B1 and F1 controll the mode of the internal PLL. If F1 is high and B1 is low, you can't use 20%Mbit/s on the LinknSpecial. What to do: 1) Make sure, your T414 is running with 25%MHz input clock. 2) Cut the PCB trail of the 25%MHz oscillator to the T414. 3) Put a divider by 5 in between. 4) Now pull pin B1 and F1 both to ground. ==> you have now a T414 without the undocumented feature. 5) Select the link speeds as desired (don't change the speed of link%0!!) 6) It should work now! We were successful, but of course, we can't take any responsibility or warranty!! Good luck, keep on working in parallel, Helmut.