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The RAM expansion slots accept 168-pin SDRAM DIMMs that are 3.3 volt, unbuffered, 8-byte, nonparity, and PC100 compliant. The speed of the SDRAM devices must be rated at 125 MHz (8 ns) or faster.
The DIMMs can be implemented with either SDRAM or ESDRAM devices. ESDRAM devices provide higher performance for random read and write operations, but SDRAM devices are generally available in larger sizes.
IMPORTANT
DIMMs with any of the following features are not supported in the Power Mac G4: registers or buffers, PLLs, ECC, parity, or EDO RAM.
The mechanical design of the SDRAM DIMM is defined by the JEDEC MO-161-D specification. 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 G4 computer is 2.00 inches.
The electrical design of the SDRAM DIMM is defined by the JEDEC standard 21-C specification. To find this specification on the World Wide Web, refer to RAM Expansion Modules .
The presence detect serial EEPROM specified in the JEDEC standard is required and must be set to properly define the DIMM configuration. Details about the required values for each byte on presence detect EEPROM can be found in sections 4.5.4 and 4.1.2.5 of the JEDEC standard 21-C specification.
Capacitance of the data lines must be kept to a minimum. Individual DRAM devices should have a pin capacitance of not more than 5 pF on each data pin.