This info is taken from NEO-AES3-6 and NEO-AES3-4 revision boards
and should be valid for all boards that have the bios to the right
of the cart slot. The older board NEO-AES which has the bios
above the cart slot is partly different.
* The 43256 (work RAM) closest to P1 joystick port
1----5V
2----GND
3----68000-12 (54), LSPC2 (21), NEO G0 (50)
4----68000-12 (55), LSPC2 (20), NEO G0 (49)
5----68000-12 (56), LSPC2 (19), NEO G0 (48)
6----68000-12 (57), LSPC2 (18), NEO G0 (47)
7----68000-12 (58), LSPC2 (16), NEO G0 (34)
8----68000-12 (59), LSPC2 (15), NEO G0 (33)
9----68000-12 (60), LSPC2 (14), NEO G0 (32)
10---68000-12 (61), LSPC2 (13), NEO G0 (31)
11---GND
12---68000-12 (62), LSPC2 (10), NEO G0 (18), 43256* (19)
13---68000-12 (63), LSPC2 (09), NEO G0 (17), 43256* (18)
14---68000-12 (64), LSPC2 (08), NEO D0 (03), 43256* (17)
15---68000-12 (01), LSPC2 (07), NEO D0 (02), 43256* (16)
16---68000-12 (02), LSPC2 (05), NEO D0 (01), 43256* (15)
17---68000-12 (03), LSPC2 (04), NEO D0 (64), 43256* (13)
18---68000-12 (04), LSPC2 (03), NEO D0 (63), 43256* (12)
19---68000-12 (05), LSPC2 (02), NEO D0 (62), 43256* (11)
20---NEO E0 (59)
21---68000-12 (29), NEO E0 (64), 43256 (10), HC259 (01)
22---68000-12 (30), NEO E0 (01), 43256 (09), HC259 (02)
23---68000-12 (31), NEO E0 (02), 43256 (08), HC259 (03)
24---68000-12 (32), NEO E0 (03), 43256 (07), HC259 (13)
25---68000-12 (33), NEO E0 (04), 43256 (06)
26---68000-12 (34), NEO E0 (15), 43256 (05)
27---68000-12 (35), NEO E0 (16), 43256 (04)
28---68000-12 (36), NEO E0 (17), 43256 (03)
29---68000-12 (37), NEO E0 (18), 43256 (25)
30---GND
31---68000-12 (38), NEO E0 (19), 43256 (24)
32---68000-12 (39), NEO E0 (20), 43256 (21)
33---68000-12 (40), NEO E0 (21), 43256 (23)
34---68000-12 (41), NEO E0 (31)
35---68000-12 (42), NEO E0 (32)
36---68000-12 (43), NEO E0 (33)
37---68000-12 (44), NEO E0 (34)
38---5V (N.C. on NEO-AES3-4)
39---5V
40---5V
Fault checking.
If for some reason the system no longer works then obiously some traces
have broken, check everything.
If the Bios is working but you get a memory card error on power up if a
memory card is inserted and a card protected error while trying to format
a memory card then one or more of the socket to NEO E0 traces have
broken (pin 20 to 37).