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!
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jsalpha2 - Tuesday, July 29, 2003 - link
Pardon me, cause I'm tired. Did the article say if 4x(256) is better or worse than 2x(512). Assuming identicle brand and speed of RAM.I think I heard somewhere to go with just two sticks for better performance. Plus then you have open slots for later.
Question #2 Would 2x(512) of cheaper DDR333 be better than 2x(256) of DDR400?
thanks
Anonymous User - Tuesday, July 29, 2003 - link
Great article, it's just missing latency benchmarks.Anonymous User - Tuesday, July 29, 2003 - link
Ok - pardon the newbie question, but - I'm building a P4c with Asus P4P800 board. I want 1 gig of DDR400 ram - what brand/model number do I buy - ?Thanks for your help.
Anonymous User - Tuesday, July 29, 2003 - link
This is all nice and good, but what does it all mean in the real world, run some benchmarks in these various modes and show us whether we should care about it :) bottom line to me is what it does for the games, if i'm losing/gaining 4 FPS i'm more likely to care about the price differences then memtest.Wesley Fink - Tuesday, July 29, 2003 - link
These are quoted form Intel's White Paper, p.13 "NOTES: Ranks per Dimm (1 Rank is a single-sided DIMM, 2 Ranks is a double-sided DIMM)". The common practice of using higher-density Dimms every other Dimm on both sides (4 chips per side) is FUNCTIONALLY a Single Bank or Single-Sided Dimm.As for confirming that 4 dimms was faster, only the tests on the 3.0 were CPU-limited. We also determined maximum overclock on a 2.4C which was not CPU-Limited. Please check Page 7.
Philippine Mango - Thursday, January 25, 2007 - link
Wrong, you didn't use a 2.4C, you used a 2.6 processor which from what I know doesn't overclock as well as the 2.8C or 2.4C..Anonymous User - Tuesday, July 29, 2003 - link
"...we confirmed that the added memory bandwidth more than makes up for the slightly lower overclock with four double-sided DIMMs"To say you 'confirmed it' is quite a leap indeed... as you notably stated, you were CPU limited in going any higher for 1 and 2 sticks, whereas you clearly reached a blockade with the 4 sticks of memory. It could be that 4 sticks of memory causes a blockade in the chipset performance at some GHz, but with a better CPU you might have gone much higher with the opposing configurations.
-Robert
Anonymous User - Tuesday, July 29, 2003 - link
"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"Can somebody help me to understand this?
I have only heard about 2 matched DIMMs...
Four matched DIMMs is 2 X 2 matched DIMMS?
Thank you very much!
Anonymous User - Tuesday, July 29, 2003 - link
While the article was interesting in that it at least confirmed Intel's white paper, I would be interested in your also testing ECC. I have a machine which does double duty as a backup server (plug the disks in the SCSI port and away it goes!). I am just curious as to the performamce hit when ECC is being used.Anonymous User - Tuesday, July 29, 2003 - link
The writer does not distinguish between DS and double bank module ;)