This little hack works nicely combined with the single Rom or multi-game hack. It can also be used if the central rom socket is empty and missed by the daughterboard, or if there is an empty socket on the daughterboard. (This can include the top of the risers that are used to plug the daughterboard in)
1. Remove the 2 * 2114's at 7N and 7P
2. Bend out pins 18,20 and 21 on a wide 6116
3. Place 6116 in 7L or 7J (or other empty socket)
4. Connect as follows: -
pins 18 and 20 to 7N pin 8 (/CS)
pin 21 to 7N pin 10 (/RW)
You now actually have twice as much program memory as you used to have ($4000-$47FF), so you can also use this trick with some of the game hacks that normally piggyback an extra 2 ram chips.