Memory is always changing, and it's usually led by processor manufacturers. DDR, for example, is now a dead-end technology. This year's new chipsets for both AMD and Intel's platforms have seen to that by switching to higher bandwidth DDR2 memory.
The architectural changes from 184-pin to 240-pin modules mean adopting the latest processor requires additional outlay on new memory modules as well. The update was necessary - since DDR reached a frequency ceiling of 600MHz - although these parts were rare and never standardised. The changes made in DDR2 mean modules can offer even higher speeds while maintaining a good yield on the chips.
That's not to say things are simple. DDR2 comes in so many varieties that it's difficult to ascertain which give the best combination of performance and value. To this end, we are comparing three different matched pairs of memory: Kingston Value RAM PC2-5300 sticks, Crucial's high-end Ballistix PC2- 6400 parts, and Corsair's premium PC2-8888 Dominator memory.
CAS latency is always quoted within memory specifi cations but its true relevance to performance can seem confusing. It's the delay, measured in CPU cycles, between the memory controller sending out a request for data and that data being sent. A lower CAS latency is more important when data is being used in small chunks requiring many requests.
The trade-off with DDR2 is that CAS latency across the board is higher than with most DDR modules, and the earliest PC2-3200 sticks performed worse than DDR equivalents. Memory frequency affects the data bandwidth, while latency affects every memory access, so it's possible that higher clocked DDR2 with greater CAS latency could end up performing worse than slower clocked memory with a lower latency.
Most DDR2 motherboards for both AMD and Intel processors support 800MHz, with cheaper models limited to 667MHz and a few offering 1,066MHz as a BIOS option. When set to run at this speed, the Dominator modules give a noticeable performance gain.
The PC2-8888 Dominator memory has other advantages even if you cannot run the memory at 1,066MHz. One big difference is the lower CAS latency - CL4 rather than the common CL5. The other advantage is greater headroom in overclocking, because when FSB frequency is increased in order to raise the CPU speed, it can also overclock the memory, causing some cheaper modules to fail.
The Dominator promises to eliminate that hurdle, as well as addressing the issue of overheating with the 40mm fans and aluminium heatsinks included with it. These additions help the expensive package stand out from other memory kits. It's yet another device drawing power, but if you're looking to invest in premium memory, you hopefully have purchased a powerful PSU already.
Crucial's 800MHz Ballistix modules are for the system builder with a more modest budget. As expected, the performance in synthetic tests was lower than memory clocked at 1,066MHz but with little difference in SYSmark 04 scores and only a small difference in Memory testing DDR2 performance is only getting better.
We put three varieties through their paces, and find out what makes DDR2 tick 3DMark 06, there's a less perceivable performance drop in real-world usage. Due to its wide support, 800MHz memory is a popular choice for DDR2-based systems and Crucial's kit shows why: low latency and high performance at a more reasonable price.
This doesn't mean Kingston's value 667MHz modules are a poor third place. Our benchmarks showed that these still deliver performance where it counts, but with a considerable saving when purchasing a capacity of 2GB. As long as this price difference remains, we expect 667MHz DDR2 to stay on shopping lists for the foreseeable future.
Intel's roadmaps tentatively point to DDR3 support in approximately 12 months' time, initially in PC3-6400 and PC3-8500 parts. As with the jump to DDR2, CAS latency on these parts will rise again and higher frequency modules than DDR2 may not arrive until 2008.
With the range of sticks on test here already in the shops, adopting now is worth it to give your system a performance boost. Orestis Bastounis