Will splashing out on expensive RAM make a real difference to PC performance? And if so, how much should you buy? We supply the benchmarks and lay the details bare
According to legend, Bill Gates once concluded that “640KB of memory ought to be enough for anyone” (a legend he’s at pains to repudiate). These days it takes more than 800 times that much RAM just to make Windows Vista work smoothly. But as the idea takes hold that more RAM is always good, we’re increasingly seeing home systems armed with a vast 4GB of storage. Indeed, with 64-bit Vista gaining traction, we’re sure the 8GB home PC can’t be far away. Is there any need for this much memory, or is it a waste of money beyond a certain point?
This month we set out to discover the truth. Armed with a comprehensive set of benchmarks and a big stack of DIMMs, we’ve tested performance on both XP and Vista to find out how much memory you really need.
But, of course, quantity of memory isn’t the only consideration. Does faster RAM make a difference? And what about issues such as latency and dual-channel architecture? Do they matter, or are they mere technical curiosities of no importance in the real world?
We’ll lay the details bare, along with explanations of the difference between DDR, DDR2 and DDR3, and how to decode RAM speeds and timings. We’ll even delve into the black art of memory overclocking. If you’re thinking of upgrading an existing system – or building one from scratch – don’t buy a DIMM until you’ve read this.
What’s the ideal amount of memory?
According to Microsoft, Windows Vista requires 512MB to install and run, while Windows XP requires 64MB. In practice, systems with these memory allocations will work, but won’t be able to keep all your active programs and data in RAM at once, so they’ll be slowed down by constant hard disk access.
The solution is to add more memory – but how much do you need for a smooth Windows experience? To find out, we used our standard 2D benchmarks, which run numerous real-world tasks in common applications including Word, Excel and Photoshop. We ran them on an Intel Core 2 Duo E8500 system, with varying amounts of RAM, and both XP Professional and Vista Home Premium. You can see the results in the graphs.
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| Vista vs XP: The RAM benchmarks |
Our results show Vista is distinctly slower than XP. With its plethora of extra bells and whistles, the newer OS makes heavier demands on the system than its predecessor, particularly the RAM. On a 512MB system, our benchmark tasks were bogged down by constant paging, and even a 4GB system couldn’t keep up with XP on an eighth as much RAM.
While adding RAM helps, the ideal amount depends on how you use your PC. For pure number-crunching, boosting memory has only a small benefit. In our audio-encoding benchmark, quadrupling Vista’s RAM from 512MB to 2GB yielded only a 1.4% speed increase. Video encoding derived a mere 5% benefit from the same upgrade. But when it came to multitasking, the benefit of more memory shone. Going up to 2GB sped things up by an astonishing 35%, and in Photoshop the improvement was more than 40%.
When we added RAM beyond 2GB, several applications saw no benefit at all, and though multitasking and graphical applications continued to run more smoothly, there was nothing like the dramatic leap you’d see in going from 512MB to 1GB, or from 1GB to 2GB. In conclusion: 2GB is the sweet spot for Vista, but if you make heavy use of your computer, you can always add more.
Is there an upper limit of RAM?
Before you splash out on a bumper pack of DIMMs, check you’re not wasting money on more RAM than your system can use. XP won’t recognise more than 3GB, so there’s no point adding extra.
With Vista, the situation is more complex: 32-bit editions can address up to 4GB of RAM, but that has to include not only your system RAM but also the memory in your graphics card and other system resources. If you install a 4GB DIMM, you’ll find less than 3.5GB available to the system. Given the diminishing benefits of adding memory above 2GB, you might want to consider saving money and sticking at 3GB.
64-bit editions of Vista can take advantage of far more RAM – the 64-bit version of Home Basic will take up to 8GB, while Home Premium supports up to 16GB and the Ultimate, Business and Enterprise editions can accommodate a massive 128GB of RAM – though good luck finding a motherboard with enough DIMM slots.