Thanks to OC Forums for this one. Helped me set up HDMI audio with my Geforce GTX 285 (needed to know where the SPDIF/out was!)
AD_EXT pin outs:
VCC +5V power supply 1 X X 2 VCC +5V power supply
GND Ground 3 X X 4 AC97CLK 24.5 MHz clock output
GND Ground 5 X X 6 GP_SPDIFIN#2 SPDIF input signal
GND Ground 7 X X 8 GND Ground
SPDIFO#3 SPDIF Out signal 9 X X 10 GPO1 General Purpose Output #1
GPO2 General Purpose Output #2 11 X X 12 GND Ground
GPO0 General Purpose Output #0 13 X X 14 GND Ground
GP_SPDIFIN1 SPDIF Input signal 15 X X 16 GND Ground
SPDIFO#0 SPDIF Out signal 17 X X 18 GND Ground
SPDIFO#1 SPDIF Out signal 19 X X 20 GND Ground
GND Ground 21 X X 22 SPDIFO#2 SPDIF Out signal
GPI0 Digital Input (GP Input 0; Reserved) 23 X X 24 GPI1 Digital Input, (GP Input 1; Reserved)
OUTMIDI MIDI Output 25 X X 26 GND Ground
INMIDI MIDI Input 27 X X 28 GND Ground
No pin 29 30 No pin
ADCSDO2 I2S audio data input 31 X X 32 GND Ground
ADCSDO1 I2S audio data input 33 X X 34 GND Ground
ADCSDO0 I2S audio data input 35 X X 36 GND Ground
I2SCLK I2S serial bit clock 37 X X 38 GND Ground
I2SFS Frame sync 39 X X 40 GND Ground
Volume Control:
Volume down 1 X
No pin 2
Volume up 3 X
Common 4 X
Firewire Connector:
?TPB-? 1 X X 2 ?TPA+?
?NC? 3 X X 4 ?TPA-?
?NC? 5 X X 6 ?VG?
?VP? 7 X X 8 ?NC?
No pin 9 X 10 ?TPB+?