Searching for the Memory Holy Grail: Part 1
by Wesley Fink on July 27, 2003 11:13 PM EST- Posted in
- Memory
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!
Facebook
Twitter
RSS
42 Comments
View All Comments
Anonymous User - Tuesday, July 29, 2003 - link
Wesley Fink - Monday, July 28, 2003 - link
Yes, you read it correctly. the mixed dimms can vary from very large drops - 20 to 27% or so - to very little if any drop for closely matched pairs. Performance seems to fare best when mixed pairs are the same capacities and the same "bank" configuration.ViRGE - Monday, July 28, 2003 - link
Very good article, Wesley, but I'm a bit confused on your mixed vs. matched DIMM comparison. On the 1st configuration, 2x256DS + 2x512DS, the timings look to be the same as in the 1st table on page 4, the DDR 400 numbers. Am I reading this correctly? It seems odd(although believable) that memory bandwidth dropped 25%, even though it stayed as 4 DS DIMMs at the same timings.PrometheusN - Monday, July 28, 2003 - link
Thanks to a reader for pointing out one correction to this article. The Intel White Paper from the 865 chart reverses 1 and 2 memory positions compared to the 875 white paper. While I did not test 865 performance in the review, I did make reference to the White Paper Chart.We can also wonder, with Intel not sanctioning PAT on the 865, exactly how the 865 boards WITH PAT will behave, and if memory on an 865 with PAT changes back to the same as 875.
Anonymous User - Monday, July 28, 2003 - link
You did not close your table on page eight.3 4 DS/td> Dual Channel
Add a < to the "/td>" ;)
Otherwise... Great article, very informing, thanks for taking the time to write this up.
PrometheusN - Monday, July 28, 2003 - link
Single-Sided or Double-Sided IS a functional description - but it normally is also a visual description. BEWARE dimms that skip every other chips on both sides. These have 4 chips on each side, but are functionally Single-Sided.PrometheusN - Monday, July 28, 2003 - link
According to CPU-Z 1.18C, 4 Sticks of ram - single or double - do NOT disable "PAT" on the DFI 875PRO or the Asus P4C800-E. It depends on how the motherboard BIOS handles the 4 Dimms.Wesley Fink
Shalmanese - Monday, July 28, 2003 - link
Nice article but what are the real world consequences of these numbers? When DDR was 1st introduced, we only saw a ~10% peroformance increase from a 100% increase in memory bandwidth so I am thinking that the difference between 2 and 4 banks would be trivial.ghg - Monday, July 28, 2003 - link
Hi PromNice review, as we expected from you 8-).
Using 4 sticks of doublesided OCZ 3700 Gold disables PAT according to CPU-Z 1.18c.
Same behavior when taking 4 sticks of singlesided OCZ 4000 ?
Ciao
Gary
ghg - Monday, July 28, 2003 - link