G5 Front Pinouts

So as to alleviate foolishness, the G5 front panel pinouts, as sourced from the 2005 Power Mac G5 Service Source manual, are:

  <--- Locking plastic notch is on this side
                1   2
              +---+---+
        25V - | o | o | - V-GND
              +---+---+
     FW TPA - | o | o | - FW TPA+
              +---+---+
 CHS GND FW - | o | o | - CHS GND USB
              +---+---+
     FW TPB - | o | o | - FW TPB+
              +---+---+
    USB PWR - | o | o | - USB GND
              +---+---+
       USB- - | o | o | - USB+
              +---+---+
        LED - | o | o | - PWR BTN
              +---+---+
AUDIO SENSE - | o | o | - AUDIO COM
              +---+---+
AUDIO RIGHT - | o | o | - AUDIO LEFT
              +---+---+

USB Pinouts

          1   2
        +---+---+
 VCC  - | o | o | - USB +5V
        +---+---+
USB0- - | o | o | - USB1 -
        +---+---+
USB0+ - | o | o | - USB1 +
        +---+---+
GND   - | o | o | - GND
        +---+---+
        |   | o | - USB Shield GND
        +---+---+


G5 6(CHASSIC GND USB)   to      10(Shield)
G5 9(USB PWR)           to      1 (VCC)
G5 10(USB GND)          to      7 (GND)
G5 11(USB-)             to      3 (USB0 -)
G5 12(USB+)             to      5 (USB0 +)

For some inexplicable reason, other people’s front panel diagrams were pretty screwed up - USB0- to USB- and USB1- to USB+ and similar. Additionally, the most “officious” (most commonly found) G5 front panel pinout had pins 11 and 12, aka USB- and USB+, reversed! According to the official Power Mac G5 Service manual, which covers the Power Mac G5, Power Mac G5 (June 2004), and Power Mac G5 (Early 2005), pin 11 is USB- and pin 12 is USB+.

Audio Pinouts

             1   2
           +---+---+
  MIC_L  - | o | o | - GND
           +---+---+
  MIC_R  - | o | o | - PRESENCE
           +---+---+
  LINE_R - | o | o | - SNS1_RETURN
           +---+---+
SNS_SEND - | o |   |
           +---+---+
  LINE_L - | o | o | - SNS2_RETURN
           +---+---+

G5 17(AUDIO RIGHT)    to        5 (LINE_R)
G5 16(AUDIO LEFT)     to        9 (LINE_L)
G5 15(AUDIO SENSE)    to        10 (SNS2_RETURN) -- one schematic tied 10 to 7
G5 16(AUDIO COM)      to        2 (GND) -- one schematic also tied in 4

Note that, according to some vague forum sources, you could also tie SNS_SEND to SNS2_RETURN to allow for selection of the device from the operating system:

G5 17(AUDIO RIGHT)    to        5 (LINE_R)
G5 16(AUDIO LEFT)     to        9 (LINE_L)
G5 16(AUDIO COM)      to        2 (GND)
G5 16(AUDIO COM)      to        4 (PRESENCE)
10 (SNS2_RETURN)      to        7 (SNS_SEND)

G5 Fan Pinouts

Definitions:

• PWM is Pulse Width Modulation
• SNS is Sense/Fan RPM
• GND is common ground
• 12V is constant +12V (obviously)
• TMP is temperature sensor

All PowerMac G5 fans use the same basic pinout of PWM, SNS, GND, 12V, from pin 1 to pin 4, respectively.

The regular hard-drive bay fan and the PCI fan use the following pinouts:

         PWM SNS GND 12V
          |   |   |   |
pin 1   +---+---+---+---+   pin 4
        | o | o | o | o |
        +---+---+---+---+

The “blower” hard-drive bay fan uses a 5-pin connector, however the 5th pin is not connected, so you can safely ignore it:

         PWM SNS GND 12V
          |   |   |   |
pin 1   +---+---+---+---+---+   pin 5
        | o | o | o | o |   |
        +---+---+---+---+---+

The front CPU fans use the following pinouts:

         PWM1 S1 GND 12V PWM2 S2 TMP- TMP+
          |   |   |   |   |   |   |   |
pin 1   +---+---+---+---+---+---+---+---+   pin 8
        | o | o | o | o | o | o | o | o |
        +---+---+---+---+---+---+---+---+

The back CPU fans use the following pinouts:

         PWM1 S1 GND 12V PWM2 S2
          |   |   |   |   |   |
pin 1   +---+---+---+---+---+---+   pin 6
        | o | o | o | o | o | o |
        +---+---+---+---+---+---+

PC Fan Header Pinouts

4-pin ATX motherboard headers, such as those used for the CPU fan are:

         GND 12V SNS PWM
          |   |   |   |
pin 1   +---+---+---+---+
        | o | o | o | o |
        +---+---+---+---+

The more common 3-pin motherboard header is the same as the 4-pin, but missing the fourth PWM pin:

         GND 12V SNS
          |   |   |
pin 1   +---+---+---+
        | o | o | o |
        +---+---+---+

G5 to PC Fan Pinouts

The basic notion is to use the PC motherboard’s 4-pin fan header to drive the G5 fans. If you do not have a 4-pin female connector, then a floppy-style molex connector will also fit the motherboard’s 4-pin header. The basic pinout for using the motherboard’s 4-pin header, in text, is:

G5 1(PWM1)      to    HDR 4(PWM)
G5 2(SENSE1)    to    HDR 3(SENSE)
G5 3(GROUND)    to    HDR 1(GROUND)
G5 4(12V)       to    HDR 2(12V)
G5 5(PWM2)      to    HDR 4(PWM)
G5 6(SENSE2)    to    NOTHING

On my Gigabyte 970A-UD3P motherboard, which uses an ITE 118620E, pin 4 was listed as “Reserved” and output around 4.97 volts constant - this imples +5V VCC, not PWM. However, when I connected all 4 pins to the motherboard, pin 4’s output dropped to around 3.5V - this is insufficient to drive “max” PWM for the G5 fans.

However, in the case that your fourth pin does not provide PWM or a constant +5V, or if you’re using a 3-pin motherboard header, then you must borrow +5V from the PSU’s molex connector. The basic schematic is:

G5 1(PWM1)      to    PSU +5V
G5 2(SENSE1)    to    HDR 3(SENSE)
G5 3(GROUND)    to    HDR 1(GROUND)
G5 4(12V)       to    HDR 2(12V)
G5 5(PWM2)      to    PSU +5v
G5 6(SENSE2)    to    NOTHING

Alternatively, one could make a circuit to convert the variable mobo header +12V to a PWM signal - G5 pin 4 would then have to be powered by a separate +12V molex pin.

If you don’t wish to power the fan(s) through the motherboard header, you can instead use a PSU molex connector only:

G5 1(PWM1)      to    PSU +5V
G5 2(SENSE1)    to    NOTHING
G5 3(GROUND)    to    PSU GROUND
G5 4(12V)       to    PSU +12V
G5 5(PWM2)      to    PSU +5v
G5 6(SENSE2)    to    NOTHING

One thing to keep in mind when powering multiple fans from a motherboard header is that the motherboard is only rated to provide a certain amount of amperage through that header - if it exceeds this amount, you can risk damaging the motherboard or the chip responsible for powering the fans. In general, it seems that each fan header provides 1 amp max, however this varies between manufacturers and models, so ensure that you do not exceed this amount.

I am unsure of the actual amperage draw of the G5 fans - standard “PC” fans use around 0.15a, and as far as I can tell, running the G5’s fans from the motherboard’s header doesn’t cause any issues, not even with dual G5 CPU fans running from the same header. I also ran the system through a watt measurement tool and could not find any actual increase in wattage - in fact, the meter measured lower values on average with the G5 fans connected (121-122 without fans, 118-120 with fans). The decrease is most likely due to the CPU fan not being forced to spin as much to keep cool.

G5 Speaker to PC Pinouts

The speaker pinouts are fairly obvious and the only thing you need to keep track of is the polarity. On the G5’s front fan/speaker combo, the 2-pin cable is for the speaker, and the wire with the white stripe down the side represents positive. Most PC motherboards use a 4-pin header plug that only has two wires attached - the pinout is:

G5 white(+)   to    HDR 1(+)
G5 black-     to    HDR 4(-)

This could vary for you, so ensure that positive maps to positive and negative to negative.