It’s commonly assumed that adding RAM improves your PC’s performance – and that was certainly true a decade ago, when most people’s PCs were starved of physical RAM and relied heavily on slow virtual memory.
To find out whether it’s still true today, we equipped our test system with a 500GB Western Digital Caviar Green drive and ran various performance tests, first with 2GB of RAM, then with more generous 4GB and 8GB allocations.
The effect is plain to see: going from 2GB to 4GB yielded an 18% overall performance boost in our Real World Benchmarks, and cut almost 40 seconds off the time it took the PC to reboot. The biggest impact was in the taxing multiple-applications test, which ran almost twice as fast with 4GB. Doubling the RAM again, to 8GB, yielded further benefits, but on a smaller scale. On a system such as this, adding memory does help performance, but once you go beyond 4GB it’s a game of diminishing returns.
What if you’re using a more modern hard disk? With a fast solid-state drive, virtual memory becomes almost as fast as physical RAM, so the benefit of extra memory is greatly reduced. After equipping our test system with a Samsung 840 Pro SSD, we found large programs such as Crysis and Adobe Photoshop opened at full speed even with only 2GB of RAM.
Our Real World Benchmarks actually ran significantly faster with 2GB of RAM and an SSD than on our 8GB system with a mechanical disk.
If you want the best performance from your PC, therefore, extra memory helps – but a fast SSD is likely to have a bigger impact.
RAM speed
DDR3 RAM officially supports operating speeds from 800MHz to 2,133MHz. The speed at which the memory chips inside a DIMM actually read and write information varies by much less than these frequencies would suggest, however – and, at any rate, memory speed is only one factor in overall system performance.
We found the performance benefit of switching from 1,066MHz RAM to 1,600MHz modules was small. It might be worth paying a little extra for faster RAM, but it won’t have a transformative effect on performance.
Single and dual channel
Modern motherboards support dual-channel memory, so if you install two identical DIMMs, the memory controller will read and write to them both at once – which sounds like it ought to double your RAM speed. To test the actual benefit, we compared a 2GB single-channel system with one using dual-channel 1GB DIMMs.
Like switching to faster memory, our results showed a benefit to using dual-channel DIMMs – especially in our Media benchmark – but on a modest scale. Most manufacturers sell DIMMs in matched pairs specifically intended for dual-channel usage, so when it comes to upgrading your system RAM it’s easy to achieve that small advantage. But if you mix and match modules – say, for example, using one 2GB DIMM and one 1GB DIMM – the slight performance penalty shouldn’t be too hard to swallow.
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