Expansion
This chapter describes the expansion features of the Power Mac G5 computer: the DDR SDRAM expansion slots and the PCI or PCI-X expansion slots.
In this section:
RAM Expansion
PCI or PCI-X Expansion Slots
RAM Expansion
The main logic board of some configurations of the Power Mac G5 computer has four pairs of DDR SDRAM expansion slots for unbuffered DDR400 (PC3200) dual in-line memory modules (DIMMs) for a maximum memory of 8 GB. The main logic board of other configurations of the Power Mac G5 computer has 2 pairs of DDR SDRAM expansion slots for unbuffered DDR333 (PC2700) dual in-line memory modules (DIMMs) for a maximum memory of 4 GB.
Each DIMM can contain 256 and 512 MB (also is capable of 128 MB, 1 GB, and has future expansion ability of 2 GB) of double data rate synchronous dynamic RAM (DDR SDRAM). At least one pair of the RAM expansion slots contains factory installed DIMMs.
Additional DIMMs must be installed in pairs of the same size. The slot pairs are numbered: J11 and J12, J13 and J14, J41 and J42, and J43 and J44; see Figure 4-1 for slot locations and numbering for both the 8-slot and 4-slot configurations. When installing additional memory, populate starting with the lowest slot pair numbers. The combined memory of all of the DIMMs installed is configured as a contiguous array of memory.
For all microprocessor speeds and for both DDR400 (PC3200) and DDR333 (PC2700) SDRAM DIMMs, the Power Mac G5 supports CAS latencies of 2, 2.5, 3, 4, and 5.
DIMM Specifications
The RAM expansion slots accept 184-pin DDR SDRAM DIMMs that are 2.5 volt, unbuffered, 8-byte, nonparity, and DDR400-compliant (PC3200) or DDR333-compliant (PC2700).
Important: DIMMs with any of the following features are not supported in the Power Mac G5 computer: registers or buffers, PLLs, ECC, parity, or EDO RAM.
Mechanical Specifications
The mechanical design of the DDR SDRAM DIMM is defined by the JEDEC specification JESD21-C, MODULES4_20_4, Release 11b. To find this specification on the World Wide Web, refer to “RAM Expansion Modules.”
The maximum height of DIMMs for use in the Power Mac G5 computer is 2 inches.
Electrical Specifications
The electrical design of the SDRAM DIMM is defined by the JEDEC specification JESD21-C, MODULES4_20_4, Release 11b. To find this specification on the World Wide Web, refer to “RAM Expansion Modules.”
The Serial Presence Detect (SPD) EEPROM specified in the JEDEC standard is required and must be set to properly define the DIMM configuration. The EEPROM is powered on 3.3 V. Details about the required values for each byte on the SPD EEPROM can be found on pages 68–70 of the JEDEC specification.
Important: For a DIMM to be recognized by the startup software, the SPD feature must be programmed properly to indicate the timing modes supported by the DIMM.
DIMM Configurations
The largest DIMM supported is a two-bank DIMM of 2 GB using 512 Mbit DDR SDRAM devices. The maximum number of devices per DIMM is 16.
Important: Power is delivered to the Power Mac G5 during sleep mode, so do not remove DIMMs while in sleep mode. A red light adjacent to the DIMM is illuminated when power is present.
Table 4-1 shows information about the different sizes of DDR SDRAM devices used in the memory modules. The memory controller supports 64 Mbit, 128 Mbit, 256 Mbit, and 512 Mbit DDR SDRAM devices. The device configurations include three specifications: address range, word size, and number of banks. For example, a 1 M by 16 by 4 device addresses 1 M, stores 16 bits at a time, and has 4 banks.
The first column in Table 4-1 shows the memory size of the largest DIMM with that device size that the computer can accommodate. The third column specifies the number of devices needed to make up the 8-byte width of the data bus. The fourth column in the table shows the size of each bank of devices, which is based on the number of internal banks in each device and the number of devices per bank.
RAM Addressing
Signals A[0–12] on each SDRAM DIMM make up a 13-bit multiplexed address bus that can support several different sizes of SDRAM devices. Table 4-2 shows the address multiplexing modes used with the devices.
PCI or PCI-X Expansion Slots
The Power Mac G5 provides three PCI or PCI-X slots via the HyperTransport bus. In some configurations of the Power Mac G5, one slot runs at a maximum of 133 MHz and two PCI-X slots run at a maximum of 100 MHz. Other configurations of the Power Mac G5 computer access all three PCI slots at 33 MHz. Each slot has room for a full size 12.335-inch or short 6.926-inch card.
The PCI-X configuration conforms to the PCI-X Specification 10B. The PCI configuration conforms to the PCI Specification 2.3.
The computer’s case has four openings in the back for access to I/O connectors on cards in the three expansion slots and the AGP slot. The numbering on the casing is 1 through 4 and corresponds to the label on the PCB. Number one is the AGP slot and numbers two through four are the PCI or PCI-X slots.
The expansion slots accept PCI or PCI-X cards with either 32-bit or 64-bit address and data buses. The expansion slots support universal and +3.3 V cards, but not 5 V signalling. The cards are required to use the standard ISA fence described in the specification.
The expansion slots support all the required PCI signals and certain optional PCI signals. The PCI slots support the optional 64-bit bus extension signals and cache support signals.
The PCI slots and the AGP Pro 8x slot carry the 3.3 V_AUX power and PME signals to allow an expansion card to wake the computer from sleep mode.
A standard AGP 3.0 8x card consumes up to 30 W. Some of the higher powered AGP Pro style cards will consume a higher amount of that power, depending on the card specifications. These cards may also physically require the usage of one of more of the PCI or PCI-X slot spaces. In such a case, the power available for the physically available PCI or PCI-X slots is reduced to compensate for the increased AGP Pro power usage over the 30W. Hence, the AGP 3.0 8x Pro slot can account for up to 75 watts of that total, depending on which card is installed. The total power available for the AGP Pro slot and the three PCI or PCI-X slots is 90 W.
Important: Before removing or installing PCI expansion cards, shut down the computer and unplug the AC power cord. The Power Mac G5 computer does not support PCI hot-plugging functionality. When the computer is powered-on or asleep, the main logic board has a red LED to warn that power is present.
To install or remove a PCI or PCI-X expansion card: turn off power to the computer, flip out the enclosure latch, open the side panel, remove the clear plastic air deflector, and remove the fan units. Remove the blank PCI fence for the appropriate slot, insert the card in the slot, and screw the card’s fence into place to secure the card.
Warning: When the system power is on or the system is asleep, a red light will illuminate if the plastic air deflector is removed. Do not continue if the red light is on. Power-off the system before continuing.
For detailed instructions on accessing the expansion slots, refer to the Apple Take Apart document for the Power Mac G5 computer.
In order to use the new PCI or PCI-X card, a driver must be installed. The driver installation procedure is documented by the manufacturer of the PCI card.
For more information on PCI or PCI-X, visit the worldwide web at
© 2003 Apple Computer, Inc. All Rights Reserved. (Last updated: 2003-08-20)