This is a long shot, but does anybody have a 1st gen iMac G4 logic board (820-1257) handy that has U33 populated? (It's not populated on my board.) I'm trying to identify the chip in the schematic, which says it's a C5003, but Google's coming up empty on that. (The only datasheet I can find for a C5003 is definitely not for the IC used in the iMac.) U33 is between the Pangea and the RAM slot.
Fingers crossed!
Fingers crossed!