NES/SNES controllers on the Xbox

Female DB-25 for each Xbox controller
Male DB-25 for each attached controller
13 wire (or more) cable for each attached controller

NES to Dreamcast mod

Xbox function DB-25 Original controller S- controller NES function SNES function
up 1 TP13 TP13 up up
down 2 TP15 TP15 down down
left 3 TP16 TP16 left left
right 4 TP17 TP17 right right
X 5 TP70 TP64   Y
Y 6 TP71 TP65   X
A 7 TP67 TP61 B B
B 8 TP68 TP62 A A
back 9 TP19 near TP20 select select
start 10 TP18 near C48 start start
left trigger 11       L
right trigger 12       R
ground 13        
white   TP72 TP66    
black   TP69 TP63    

Connection points for the original controller (bottom of pcb):
duke bottom

Original controller trigger and ground connections (top of pcb):
duke top

Connection points for the S-controller (bottom of pcb):
s bottom

S-controller trigger and ground connections (top of pcb):
s top

S-controller digital pad connections:

SNES controller connections (remove the chip first):

contrasuper metroid