Please reference the manual here:
http://www.kill-9.it/guido/sgi/o2-wks-hw-reference.pdf
PDF page 113, print page 97 starts the troubleshooting section. Read the ENTIRE section before fiddling with the O2.
The jumper I am referencing is covered from PDF pages 122-124 (print pages 106-108).
Some online resource refer to this as the "power bypass jumper" but the documentation says "the jumper" as there is only ONE on the entire board. The location of the jumper is near the RTC for a 5200 CPU and another location for the R10K.
WARNING, WARNING, WARNING (I cannot place enough warnings here...please read this ahead of everything). O2 has a design flaw the can cause serious mainboard damage if you won't follow the proper power-off steps. I will tell you steps that are OVERBOARD that I use to ensure I NEVER EVER have board damage. Others may disagree that some of these steps are needed. For a new user, I believe they are and am stating them for protection. If you intend to remove the mainboard of ANY O2 station you MUST, unplug the PSU from the wall and (optional..what I do) then gently remove the PSU plastic grill (keep it off until all troubleshooting is done), use the PSU lever to pop the PSU out of the back about 1" or more, THEN you may work on unlatching and removing the mainboard safely. Reverse these steps for reassembly, insert Mainboard, then reinsert PSU, then plug AC cable back into PSU.
Just like a car battery, PSU MUST come OUT FIRST, and GO IN LAST (AC cable is actually first/last but PSU immediately follows) before work. DO NOT, for any reason, remove the mainboard while your PSU is inserted/plugged in. Many people will say simply unplugging it is enough. I always suggest going further and popping is out just a smidge in case you're going very fast and it still have charge in it from a recent startup. Many O2 mainboards have been lost from people removing the mainboard will off by AC plugged in, unknown amount from going too fast from AC unplug to removing board...my recommendation skips them all. Take your time...do not rush it...plastics are old so be gentle and stop if things aren't doing what they are supposed to.
A word of caution if you use non-standard boot variables of some kind this jumper will affect boot and maybe PROM variables, I'm not responsible for any changes in your system if you fiddle with this jumper. It's not known to do any permanent damage but depending on what you find (it was left on and you remove it, or whatever...things could change). Please do this at your own risk.
Please note the factory default (correct) installation is to have the jumper on a single pin and NOT shorting the two pins. If it's shorting the two pins that's the password bypass mode is in effect (as a troubleshooting tool). If the previous owner ONLY got it to boot with that jumper enabled there will be further steps to getting things settled correctly.
Also you may need to ensure you DO NOT have a PROM password BEFORE you fiddle with this jumper. Just in case one it presented to you during troubleshooting (you've already cleared it beforehand). Please see the manual I linked to for that as well.
NEED -> 