If I'm reading the schematics correctly (and haven't missed something), it seems the A12 line passes by the following chips on the way to the ram slots (other ram lines routes through the chips in parenthesis).
UI5
UI3 (+ UJ3, UI2, UJ2, UI4,UJ4,)
RP5 (+ RP4, RP6)
UI8
VIA1
VIA2
I'll start with...