I did this this afternoon. I thought I might come in handy for those doing the CV BIOS mod. I've checked and doublechecked this, but if FABombjoy, John Soper, DoubleDown or anyone else want to double check it for me that would be great!

Note- cartridge slot (”CS”) is numbered according to IC numbering designation, assuming same orientation as BIOS eeprom.
Note- U20 has inverted orientation to most other board IC’s. This guide uses accurate numbering for that IC.

BIOS eeprom pin Destinations

1 - 5V
2 – CS-27
3 – CS-3
4 – U6-3, CS4
5 – U6-2, CS5
6 - U3-3, CS7
7 – U3-4, CS8
8 – U3-7, CS10
9 – U19-19, CS11
10 – CS12
11 – U3-14, U19-18, CS13, U20-10
12 – U3-13, U19-17, CS14, U20-11
13 – CS15, U20-12
14 – C89 (ceramic cap)
15 – U19-15, CS17
16 – U19-14, U4-14, CS18, U20-13
17 – U19-13, U4-13, CS19
18 – U19-12, U4-12, CS20
19 – U19-11, U4-11, CS21
20 – WJ4, U5-15
21 – CS23
22 – WJ4, U5-15
23 – WJ5, CS22
24 – U4-15, CS28
25 – U4-16, CS29
26 – 5V
27 – 5V
28 – 5V


If this checks out, it could be a good addition to the Knowledge base.