General Information

DDR Memory

In the Power Mac G5, PC3200/400 DDR-SDRAM DIMMs must be installed in pairs of equal size and speed. Memory from older Macintosh computers is not compatible. Do not try to install non-DDR memory as it will not fit in the DIMM slots and could cause damage.

The computers ship with a minimum of 256 MB of RAM, provided by a pair of 128 MB DIMMs installed in the two DIMM slots marked "1." You can add DIMMs, provided they are installed as a pair of equal size, in the two DIMM slots marked "2." A diagram on the logic board near the DIMM slots illustrates how the pairs must be installed.

Power Mac Logicboard Led

Results of Mixing PC2100, PC2700, and PC3200 RAM

The table below describes what happens if you install PC2100, PC2700, or PC3200 memory in the Power Mac G5 computer.

When only PC2100 DIMMs are installed

The computer makes three single tones instead of the startup sound. The LED on the front of the computer flashes three times, and the computer does not startup.

When a mix of PC2100, PC2700, or PC 3200 DIMMs is installed

The computer starts up normally, but neither the computer nor Apple System Profiler recognizes the PC2100 memory.

When no memory is installed or memory is not installed correctly

The computer does not make a normal startup sound. Instead, there is a single tone, and the computer's front LED flashes about once every 5 seconds.

PCI and AGP Cards

Power Mac G5 computers have four expansion card slots, three of which accommodate Peripheral Component Interconnect (PCI) cards and one that accepts an advanced graphics port (AGP) video card. AGP cards and PCI cards have different connectors, so you cannot insert a PCI card into the AGP slot.

Note: Maximum power consumption for all four expansion slots (the three PCI expansion cards and the AGP card) should not exceed 90 watts (W).

Mac Mini Ram Slot Repair

AGP Cards

The AGP video card, installed in slot 1, contains the graphics processor unit (GPU) and provides the computer's display ports. Slot 1 is designed specifically to accept AGP cards.

Note: Certain high-performance AGP graphics cards, when installed in slot 1, block access to the adjacent PCI slot. In this case, PCI cards can be installed in slots 3 and 4 but not in slot 2.

PCI Cards

The remaining three expansion slots, labeled 2, 3, and 4, accommodate PCI cards up to 12 inches long. The PCI slots can accommodate mixed-voltage (5.0 V, 12 V, or 3.3 V) cards but only at 3.3 V signaling, with 32-bit or 64-bit data widths and a 33 MHz frequency. You can add a 66 MHz card to a 33 MHz PCI slot if the card can operate at the lower 33 MHz rate.

Warning: Installing PCI cards that function only at 66 MHz could damage the computer. However, cards that run at both 66 MHz and 33 MHz may be installed. Check with the card's manufacturer to see if a 66 MHz card also works at 33 MHz.

Block Diagram

GPUL PowerPC Processor 10S process

GPUL PowerPC Processor 10S process

Power Mac Dual Fan Wiring Diagram

Internal Speaker

Ethernet FireWire B FireWire A RJ-45

Internal Speaker

Ethernet FireWire B FireWire A RJ-45

FireWire A y Front Panel

Resetting the Logic Board

Many system problems can be resolved by resetting the logic board. Because the Power Mac G5 (Late 2004) uses a System Management Unit (SMU) controller chip rather than a Power Management Unit (PMU) controller chip, the logic board does not include a reset button. Instead, to reset the logic board, do the following:

  1. Shut down the computer.
  2. Unplug the computer from its power source.
  3. Wait 15 seconds.
  4. Plug the power cord back in, and turn the computer on. If the computer does not power on, there is something else wrong with it; refer to the "Startup Failures" section of "Symptom Charts" in this chapter.

Note: The above procedure resets the computer's PRAM. After resetting the logic board, be sure to reset the time, date, and other system parameter settings.

RAM and Processor Verification: Power-On Self Test

A power-on self test in the computer's ROM automatically runs whenever the computer is started up after being fully shut down (the test does not run if the computer is only restarted). If the test detects a problem, the status LED located above the power button on the front of the computer will flash in the following ways*:

  • 1 Flash: No RAM is installed or detected.
  • 2 Flashes: Incompatible RAM types are installed.
  • 3 Flashes: No RAM banks passed memory testing.
  • 4 Flashes: No good boot images are detected in the boot ROM (and/or there is a bad sys config block).
  • 5 Flashes: The processor is not usable.
  • Note: The status LED lights up when the power button is depressed at startup. Do not count this light as one of the diagnostic flashes.

Front Panel Board Troubleshooting

Certain no power symptoms can sometimes be caused by a failed front panel board or power button. However, troubleshooting these parts by swapping them out with known-good parts can be time-consuming. An alternative approach is to build a simple front panel board troubleshooting tool, as illustrated, and then use the procedures described below to test the board and button before actually replacing them.

The tool consists of a known-good front panel board, with a known-good power button and front panel board cable attached.

To use the tool in troubleshooting the front panel board and power button, do the following:

  1. Shut down the computer.
  2. Disconnect the installed front panel board cable from the logic board.
  3. Connect the front panel board cable from the troubleshooting tool to the logic board.
  4. Try to start up the computer by pressing the power button on the troubleshooting tool.

Then proceed with the front panel board troubleshooting steps as described in the "Symptom Charts" in this chapter.

Power Supply Verification

To power on, the computer's logic board requires a "trickle" power of +5V. If the system fails to power on, first reset the PMU. Then follow the procedure outlined below to determine whether the problem is related to the power supply.

Note: To verify the power supply, you need a volt meter.

  1. Remove the power cord from the computer.
  2. Open the computer, lay it on its side with the access side facing up.
  3. Remove the front inlet fan assembly.
Mac Power Supply Pinout

Remove the black plastic cap covering the 24-pin power supply cable connector (the P1 or largest connector). The cap fits tightly over the connector. To remove it, rock the cap gently forward and backward as you lift up.

Note: This is a top view of the connector when it is plugged into the logic board

Note: This is a top view of the connector when it is plugged into the logic board

  1. Press the release latch on the power supply connector and disconnect the cable from the logic board.
  2. Plug a known good power cord into the computer. Do not turn on the computer.
  3. On the power supply cable connector: connect the black lead of the volt meter to pin 23 and connect the red lead of the volt meter to pin 1.

Note: This is a bottom view of the connector when it is unplugged and facing up.

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The volt meter should measure approximately +5V. If you do not get a reading of +5V, recheck the volt meter connections and measure the voltage again. If the voltage is still not present, replace the power supply.

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