the iisi uses some of the onboard ram as video memory, so it is crucial that there is memory in the slots so it can operate with a usable amount of memoryLooking for some guidance on what to check etc.
I have a IIsi that will only boot when it has simms in all 4 slots. Remove the simms I get chime but no boot. Note this logic board has 1mb-8 chips on board. Could this be the issue?