Important:
- The required RAM speed is listed on the serial label in your computer as either 333 MHz or 400 MHz.
- Use only the speed specified. Slower RAM (for example, PC2100) will not work in this computer.
- DDR SDRAM DIMMs must be installed in matched pairs. "Matched" in this context means that the two DIMMs have the same capacity and speed. A valid pair would be two 512 MB PC2700 DIMMs, for example.

Figure 1 Matching pairs of DIMMs
- DIMMs are already installed in these two slots.
- Install additional DIMMs in these two slots first.
- If slots are available and you want to install more memory, install additional DIMMs in a similar fashion: in pairs, one per bank, from the center outward.
RAM requirements and capacities
| Model of Power Mac G5 | No. of DIMM slots: | Max Total RAM: | RAM Speed: | RAM Type: | RAM Module Size | Compatible DIMM capacities: |
|---|---|---|---|---|---|---|
| 1.6 GHz Power Mac G5 |
4 | 4 GB | PC2700 | DDR SDRAM | 184-pin DIMM | 128MB, 256MB, 512MB, 1GB |
| 1.8 GHz, Dual 1.8 GHz, Dual 2.0 GHz Power Mac G5 |
8 | 8 GB | PC3200 | DDR SDRAM | 184-pin DIMM | 128MB, 256MB, 512MB, 1GB |
| Dual 1.8GHz Power Mac G5 (June 2004) |
4 | 4 GB | PC3200 | DDR SDRAM | 184-pin DIMM | 128MB, 256MB, 512MB, 1GB |
| Dual 2.0 GHz, Dual 2.5GHz Power Mac G5 (June 2004) |
8 | 8 GB | PC3200 | DDR SDRAM | 184-pin DIMM | 128MB, 256MB, 512MB, 1GB |
| 1.8GHz Power Mac G5 (Late 2004) |
4 | 4 GB | PC3200 | DDR SDRAM | 184-pin DIMM | Up to 1GB |
| Dual 2.0 GHz Power Mac G5 (Early 2005) |
4 | 4 GB | PC3200 | DDR SDRAM | 184-pin DIMM | Up to 1GB |
| Dual 2.3 GHz, Dual 2.7 GHz Power Mac G5 (Early 2005) |
8 | 8 GB | PC3200 | DDR SDRAM | 184-pin DIMM | Up to 1GB |
| Dual 2.0 GHz, Dual 2.3 GHz, Quad 2.5 GHz Power Mac G5 (Late 2005) |
8 | 16 GB | PC2-4200 | DDR2 SDRAM | 240-pin DIMM | Up to 2GB |
Learn more
Note: When purchasing DDR SDRAM for use in Macintosh computers, make sure the memory vendor conforms to the JEDEC (Joint Electron Device Engineering Council) specification. Check with your memory vendor to ensure that the DDR SDRAM supports the correct timing modes and that the Serial Presence Detect (SPD) feature has been programmed properly, as described in the JEDEC specification.