(osum tucnaku)

Our Special Hardware Used in Linux Cluster MAGI



Motivation

It is mad to make hardware in your lab today. It's long time you have forgotten how those re- and tran-sistors work and how to solder them. However, sometimes it happens that...
... that you do not like to walk to your supercomputing cluster and push all those buttons to switch power ON or OFF, and you would like it to happen somehow automatically when there is power outage. (FYI, when we put everything on one common switch and switch it ON, the only effect is test of all breakers in our lab.) The net result: We decided to create hardware which would enable one cluster node to switch power for the rest ON and OFF.

Realisation

It is relatively easy with ATX cases we used - there is electronic power switch which is normally controlled using pushbutton but can be controlled using optron as well (soldered parallel to it) and there is poweron LED which shines quite well also with another optron's LED in series - so using two optrons you can sense current state and change it if you like. Normal parallel printer port was quite enough to control 7 other computers (would be enough for 16 as well if you like).

We added 15-pin male Cannon connector to every machine and soldered optrons directly on it. It exactly fits to hole prepared for gameport (you are not going to use dozen joysticks on your supercomputing cluster, are you?). To avoid any confusion, we've chosen male connector (gameport connector is female). All the rest fits on small board pluged into one printer port - two transistors, five resistors and plenty of silicon diodes. You even do not need power supply for it!

If you absolutely must know how is it done, look here, but please keep in your mind that I made absolutely no effort to make it flawless beyond my own needs. (Once it worked for me, I let it be. If something was already soldered, I let it in place, even thought now I would know better ways to do it. But I did it once only and optimized design&research accordingly. For example I soldered wnong cable in a wrong place and fixed it in software because it was easier for me. I warned you.)


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