There are many variables to consider when purchasing RAM, with frequency and latency being just two. But with malfunctioning RAM one of the most common causes for system instability, we’ve persuaded some manufacturers on test to disclose RMA and tested fail rates figures too; the former being how many modules are returned by customers, the latter being how many of those returned modules then prove faulty at the factory. All the modules come with lifetime warranties.

Now that the latest AMD and Intel platforms both support DDR2 RAM, this is what we’ve focused on. The maximum frequency supported by both the memory controller in AMD AM2 processors and by Intel’s north bridges is 800MHz. However, we’ve also tested 533MHz and 667MHz RAM to get an indication of how much performance you lose and how much cheaper these modules are in comparison. We tested twin memory modules, as that’s the best way to upgrade your memory.

To test, we unleashed the usual six tortuous runs of our benchmarks on each set of RAM, followed by our Call of Duty 2 (CoD2) test at 1024 x 768 with Extra textures. Our graphics card was easily capable of running CoD2 at this resolution, but with only 256MB of onboard memory, the 512MB textures needed to be cached in the system RAM. We tested in both an Intel and an AMD test rig and gave ratings accordingly.

Faster RAM generally gives faster overall performance on both systems. However, while the Crucial 667MHz sticks performed poorly on both our Intel and AMD systems, the Crucial 533MHz RAM actually performed identically to the Crucial 800MHz on the Intel system, its lower latencies more than compensating for the lower bandwidth. As such, it’s a bargain if you’re on a tight budget for an Intel system, although our gaming benchmark suffered from the lack of bandwidth. Order via Crucial’s Memory Advisor Tool to avoid being charged an extra 20 percent if you make a warranty claim, and note, although cheap if you’re buying from the Crucial website carriage costs approach $40; disappointingly, Crucial couldn’t tell us its RMA or tested failure rate figures.

You can’t get away with skimping on RAM speed with AMD systems as much, with the integrated memory controller in the CPU proving to be fussy about the quality of RAM used. Here, the tight latencies of the Super Talent 800MHz and Crucial Ballistix 800MHz memory proved superior, but both have complications.

Despite being labelled as 800MHz, Super Talent supplies its RAM clocked at 667MHz to ‘ensure compatibility’. You need to manually force it to run at 800MHz from the BIOS, with tight 4-4-3-8 latency timings. This is essentially a guaranteed overclock, but it isn’t mentioned on the packaging. We’re also wary of the high tested failure rate.

The Crucial Ballistix RAM will also require BIOS tweaking on some motherboards, as it can only run at 2.2V rather than the standard 1.85V. With the Intel system, we had to overvolt another set of RAM and then swap the Ballistix in before it would even boot. Marks were docked accordingly.

The Kingston Hyper-X 800MHz kit is quoted as running at 4-4-4-12 latencies, which again needs to be forced in the BIOS. This overclock failed on the AMD system despite overvolting. It was still fast at its reported SPD latencies (5-5-5-16), and would have challenged for an award if it weren’t for the price. Even the extra marks gained from the low RMA and fail rate don’t justify the cost.

And although the ADATA DDR2-800MHz RAM (only sold individually, not in pairs) was fast, the high RMA figure lost it the marks that would have let it match the Corsair XMS2 TWIN2X1024A-6400 kit. Excellent performance even at 5-5-5-18, a good price and impressive RMA and fail test figures make this our best buy.