I just finished installing one on my Rev5. You'll need TWO jumpers, actually.
It all boils down to putting the address lines of the chip to the right spots in the socket. The earlier REV boards (<=5) need two wires, the REV 6 needs one, and later boards (>=6a?) don't need a jumper at all.
The only things you'll need are a soldering kit (Radio Shack has a basic one for about $8-10) and some thin (24-30 gauge) wire, about 6" (18cm) long, cut to a 2" (5cm) section, and a longer 4" (10-12cm) section.
Step 1: Remove ROM from socket. If there's a wire jumpering pins 1-31, then unsolder the wire from pin 1, leaving the connection to pin 31 for the next step.
Step 2: Bend out (or up) pin 31, and solder wire from this to pin 21. (This jumpers the A18 to VCC.)
Step 3: Solder wire to pin 1, making it about 3-4 inches (~9-12cm) in length, to help with the next step (it's tricky!). Leave other end free, but stripped of ~1/4" (6-7mm) insulation.
Step 4: We're done soldering, so you can unplug the thing and let it cool. Now, place the ROM close enough to the socket, as if you were going to insert it. See where pin 31 would've gone in had we not bent it out of the way? That's where the wire from pin 1 is going to go. So, carefully wedge the wire into the socket at pin 31 (this is why we used an extra long jumper). Once in, you can now insert the ROM into place, making sure that the pin 31 of the chip DOES NOT make contact with the wire we just wedged into the socket's pin 31. (This jumpers the ROM's A19 to the socket's A18).
Step 5: Double-check your work. The ONLY pin sticking up is pin 31. The gap in the socket at pin 31 should be used by the wire to pin 1, and the "stuck-up" pin 31 should be wired to pin 21. Once verified, cross your fingers and power it up.
It only took me about ten minutes, including the time to warm up the iron, to do this mod. It worked the first time (after using an unjumpered ROM, the standard jumpered ROM, and finally finding this tutorial for REV 5s).
Good Luck...
banzai
