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).