Last weekend I upgraded the RAM in my iMac from 1 GB (two 512 MB sticks) to 2 GB (two 1024 MB sticks) (in case you're curious, I'm using Mushkin RAM). While it's not been a huge improvement overall (Safari leaks memory just as fast as before), the extra RAM has made Aperture a lot faster; I no longer cringe when I start editing photos in Aperture.
While I was replacing the RAM I thought it might be interesting to see if it's important to have matched RAM (in this case two 512 MB sticks or two 1024 MB sticks) or whether unmatched RAM (one 1024MB stick) runs just as fast. Of course, I'm using Geekbench 2 as my benchmark program.
Setup
- iMac (Late 2006)
- Intel Core 2 Duo @ 2.0GHz
- 1.0 GB 667 MHz DDR2 SDRAM (2 x 512 MB) or
- 1.0 GB 667 MHz DDR2 SDRAM (1 x 1024 MB) or
- 2.0 GB 667 MHz DDR2 SDRAM (2 x 1024 MB)
- Mac OS X 10.4.9 (Build 8P2137)
I'm reporting the baseline score, rather than the raw score, for each benchmark (where a score of 1000 is the score a Power Mac G5 1.6GHz would receive). Higher is better.
Results
Overall Performance
| iMac (Late 2006) 2 x 512 MB |
2650 | |
| iMac (Late 2006) 1 x 1024 MB |
2607 | |
| iMac (Late 2006) 2 x 1024 MB |
2651 |
Integer Performance
| iMac (Late 2006) 2 x 512 MB |
2243 | |
| iMac (Late 2006) 1 x 1024 MB |
2160 | |
| iMac (Late 2006) 2 x 1024 MB |
2244 |
Floating Point Performance
| iMac (Late 2006) 2 x 512 MB |
3776 | |
| iMac (Late 2006) 1 x 1024 MB |
3794 | |
| iMac (Late 2006) 2 x 1024 MB |
3783 |
Memory Performance
| iMac (Late 2006) 2 x 512 MB |
1939 | |
| iMac (Late 2006) 1 x 1024 MB |
1928 | |
| iMac (Late 2006) 2 x 1024 MB |
1936 |
Stream Performance
| iMac (Late 2006) 2 x 512 MB |
1563 | |
| iMac (Late 2006) 1 x 1024 MB |
1383 | |
| iMac (Late 2006) 2 x 1024 MB |
1545 |
Conclusion
Overall, it doesn't look like matched RAM offers a huge performance difference over unmatched RAM (save for the Stream benchmarks which measure raw memory bandwidth, in which case matched RAM is slightly better); if you have to choose between more RAM or matched RAM, I'd argue that you're better off choosing more RAM (especially if you're using Aperture).