Dennis, I think you mentioned in another thread that your IIci is working well now except that you still must have a ROM SIMM installed for it to boot.
If you are up for some tedium, you can figure out where the problem lies pretty easily (but with said tedium).

The signals on the ROM chips are all duplicated in the ROM SIMM socket. So if you get the pinout for the ROM chips (it's identical (except for WE_ and Vpp) to a same capacity Flash or EEPROM chip) you can test continuity on all their pins to the ROM socket. If there's isn't continuity, then that's the trace to follow. The ROM socket pinout is available in "The Guide to the Macintosh Family Hardware", I think. Someone may have put it online by now. You might check Gamba's site.

Click to expand...

I've played with this a bit, but it appears that the onboard ROM address/data pins are not directly connected to those pins in the ROM SIMM slot. I can't find any visible or electrical continuity. I suppose I need to inspect the board more closely, but it appears that the onboard ROM is connected through a very large IC and the ROM SIMM has a more direct pathway to the processor. i.e. The ROM slot and RAM slots have pins in common, but the ROM slot and the onboard ROM chips don't appear to be directly connected.

I'll definitely take a closer look as time allows, though. This Mac was exposed to extremely cold temperatures for several winters, so I'm almost wondering if that could have affected the ROMs. Unlikely but maybe something to consider. One single flipped bit could easily cause complete ROM failure.

I noticed that without a SIMM installed, adding/removing the ROM SIMM jumper determines if the screen will be black or if it will be checkerboard. That doesn't really mean anything but it could come up as a clue or lead to theories as I examine this thing more closely. No detail is too fine to be noticed in this matter.