Searching for the Memory Holy Grail: Part 1

Conclusion

If you plan to run DDR400 as your base memory speed with an 800FSB processor, your best memory performance will clearly be with four matched double-sided DIMMs. Our tests, confirmed by Intel White Papers, show these configurations ranked from fastest to slowest performance on an Intel 875 Canterwood or 865 Springledale chipset motherboard.

DDR400 (1:1) Performance	DIMM Configuration	Single-Channel or Dual-Channel
1	4 DS	Dual Channel
2	2 DS or 4 SS	Dual Channel
3	2 SS	Dual Channel
4	4 SS/DS Mixed Matched Pairs	Dual Channel
5	Any DS	Single Channel
6	Any SS	Single Channel

You can run mixed matched pairs of DIMMs. That is, two of one type and size and two of another type and size, but the performance can be significantly lowered. In our tests of mixed pairs, performance decreased 22% to 25% compared to four matched double-sided DIMMs.

If you do plan to use single-sided DIMMs, then make sure you run four matched DIMMs. A pair of single-sided DIMMs ranked third in our performance tests, and was almost as slow as mixed pairs.

The situation changes if you plan to run a 533FSB P4 Processor, or if you intend to run your memory at 333 or 266 Base (5:4 or 3:2 ratio). With a 533 CPU or asynchronous 5:4 or 3:2 memory ratio, the best performing memory configuration is two double-sided DIMMs. Based on Intel White Papers, memory performance with a 533CPU or 5:4/3:2 (333/266) is ranked from best to worst.

DDR333/266 Performance	DIMM Configuration	Single-Channel or Dual-Channel
1	2 DS or 4 SS	Dual Channel
2	2 SS	Dual Channel
3	4 DS	Dual Channel
4	4 SS/DS Mixed Matched Pairs	Dual Channel
5	Any 1 or 2 DS or SS (1 DIMM or 1 in each Channel)	Single Channel
6	Any 1 SS	Single Channel

While four DIMMs do not overclock quite as well as two DIMMs on an 875/865 board, we confirmed that the added memory bandwidth more than makes up for the slightly lower overclock with four double-sided DIMMs.

Now that we have determined the best Memory Configurations for 875/865 motherboards, we will look at the best performing high-speed memory in Part 2 of Searching for the Memory Holy Grail. Since we are still waiting for several new releases of DDR466 and DDR500 Memory, it will be several weeks until we can publish a reasonable comparison of the latest in high-speed memory. Stay tuned!