If you put a sun3 board on a table with the extractor levers and serial connectors to your left, on the right will be P1 farthest away from you (on "top"), P2 in the middle, and P3 on the bottom.
We can supply power to the board through pins on the P1 ("upper") connector. Each row of pins is designated by the letter a, b, or c. Then the pins are numbered top to bottom.
The mating connector I have for P1 is nicely labeled. The "a" row is towards the back of the board and the "c" row is towards the front.
5 volts -- a32, b32, c32 -12 volts -- a31 +12 volts -- c31 Ground -- a9, a11, a15, a17, a19 Ground -- b20, b23 Ground -- c9
I connect a 10 amp supply. No good. The 5 volt supply voltage drops to 2.9 volts. More current is needed.
I get brave and use a 33 amp capable Sorensen DCS33-33E lab supply. I set the voltage to 5.0, check with a meter and fire it up. I have to increase the current limit and it pulls about 12 amps.
But the board does not run. All the DIAG lights come on and stay on. I measure voltage on the board and see 4.4 volts. So I carefully turn up the voltage on the Sorensen to 5.6 volts. Now the board runs and I measure 4.84 volts on the board. It is pulling 12.1 amps.
The Sun Field Engineer manual says that it pulls 15.2 amps of 5 volts.
Tom's Computer Info / tom@mmto.org