OS on the chip? lol are you kidding me? The only thing on the chip is data from the manufacturer to tell the chip how, when, and what code to put out. There are updates for newer firmware but no OS. Most of those boards are cheap knockoffs of such boards like teeny+ boards. What probably happened is the guy who did it, is an amateur and has no clue how to solder. Those chips merely mimic code from the ps2 and tell it that no matter what is in the drive, it has the Sony PS2 signature and it is authentic. From what I know, and I have done 30+ mod chips on ps2 alone, let alone other consoles,(wii, xbox, gamecube) there is anywhere from 17-22 wires to solder depending on your console for this specific chip. Since you said it was a fat one with the 30000 I would say it needs 17 wires to be solder right. Open it up yourself and check all the solder points on the chip it self and the ps2 to assure correct connection to the contact points. You can always find diagrams of the chip online and where the wires need to be routed to and soldered to.


P.S.
You said you have fat model...buy a network adapter and a HDD and burn games onto the HDD...it literally cuts loading times of in game material into a third.
You will need this anyway whenever your drive decides to crap out.

Hope that helps