Specifications

70 Chapter 5
Installing Memory
You can install additional dynamic random-access memory (DRAM) in packages called
Dual Inline Memory Modules (DIMMs) in the three DRAM DIMM slots on your computer’s
main logic board. You can expand your computer’s DRAM to a maximum of 1536 megabytes
(1.5 gigabytes). To check the amounts of DRAM installed, use the Apple System Profiler
(located in the Utilities folder, in your computer’s Applications folder).
If you install 512 MB DIMMs, they must have 256 megabit (Mbit) devices. You can also install
256 MB DIMMs that have 256 Mbit or 128 Mbit devices. You can install different size DRAM
DIMMs in any order in any DIMM slot. To check the compatibility of your DIMMs, see the
Macintosh Products Guide on Apple’s Web site: www.apple.com/guide
DIMMs must fit these specifications:
m “PC-133” Synchronous DRAM (SDRAM)
m 3.3 volt (V)
m 64-bit wide, 168-pin module
m Maximum number of memory devices on a DIMM is 16.
m Unbuffered; do not use registered or buffered SDRAM.
m Height must not exceed 2.0 inches.
Note: When purchasing DRAM for use in Macintosh computers, make sure that the memory
vendor conforms to the JEDEC specification. Check with your memory vendor to ensure that
the DRAM DIMM supports the correct timing modes and that the Serial Presence Detect (SPD)
feature has been programmed properly, as described in the JEDEC specification. You can
purchase Apple-branded memory online from the Apple Store: store.apple.com
Important DIMMs from older Macintosh computers may not be compatible with your
Power Mac G4. Only “PC-133” DIMMs are compatible. Do not use older DIMMs even if they
fit into the DRAM DIMM slots.