The Power Mac G4 (Mirrored Drive Doors) computer comes in two different models. One has a 133 MHz system bus, which uses PC2100 RAM (memory). The other has a 167 MHz system bus, which uses PC2700 RAM. If you install the wrong RAM in the computer, it may not start up, or recognize the memory.
133 MHz System Bus Model
- When only PC2700 or a mix of PC2700 and PC2100 DIMMs is installed:
The computer starts up normally and behaves as though PC2100 DIMMs are installed.
- When no memory is installed:
The computer does not make a normal startup sound. Instead, you hear a single tone, and the LED on the front of the computer flashes continuously.
167 MHz System Bus Model- 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 and PC2700 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:
The computer does not make a normal startup sound. Instead, you hear a single tone and the LED on the front of the computer flashes continuously.
Important: DDR-SDRAM is closely correlated with your computer's system bus speed. Use PC2100 DDR-SDRAM for 133 MHz system bus Power Mac computers and PC2700 DDR-SDRAM for 167 MHz system bus Power Mac computers. Do not try to install non-DDR memory into the Power Mac G4 (Mirrored Drive Doors) computer as it will not physically fit in the DIMM slots. If you do so, you could damage the logic board.