DDR2 Roundup: Reaching for 667 and Beyond
by Wesley Fink on July 8, 2004 12:09 AM EST- Posted in
- Memory
tRAS and DDR2
It made little sense to test 8 new DDR2 modules at memory timings that were less than optimal for best performance. We were able to verify quickly that the traditional CAS, Ras-to-Cas delay, and RAS Precharge timings all improved performance as timings were lowered. However, tRAS at 11 or 12 is a significant departure from the best timings that we have seen with DDR on the Intel platform - it is more like the 9 to 11 optimal tRAS seen on current AMD chipsets/processors.To determine if 11 or 12 is the best tRAS timing for DDR2, we first ran Memtest86, a commonly used memory tool that measures memory bandwidth from a custom bootable OS. Memtest86 showed absolutely no change in memory bandwidth in the range of 4 to 15 when memory timings were fixed at 4-4-4 and only tRAS was varied.
To further check our Memtest86 results, we ran a complete series of tests with Aida 32, which is also available for free download on many shareware sites. The Aida 32 memory test module is very useful because it reports both memory Read and memory Write operations as separate results. We ran both tests and also added a Total Memory Bandwidth to offer a better comparison of the test results.
Micron PC2-4300U - 4-4-4-tRAS | |||
tRAS | Aida 32 Read |
Aida 32 Write |
Aida 32 Total |
4 | 5316 | 2328 | 7644 |
5 | 5264 | 2338 | 7602 |
6 | 5289 | 2341 | 7630 |
7 | 5289 | 2326 | 7615 |
8 | 5302 | 2340 | 7642 |
9 | 5303 | 2349 | 7652 |
10 | 5314 | 2344 | 7658 |
11 | 5303 | 2344 | 7647 |
12 | 5289 | 2336 | 7625 |
13 | 5303 | 2339 | 7642 |
14 | 5264 | 2334 | 7598 |
15 | 5289 | 2275 | 7564 |
As you can see clearly, over the full range of tRAS 4 to tRAS 13, there is virtually no difference in memory performance when tRAS is adjusted. While there is a slight falloff at tRAS of 14 and 15, it is still minor. We can conclude that a tRAS setting of 4 to 13 makes no difference in memory performance. Since higher tRAS settings usually mean better memory stability, we can well understand why a 12 setting is standard. For our memory tests, we chose a value of 10, which represents the upper mid-range of best performance and stability. However, we did find that some high density (1GB) memory modules that were not included in our tests performed with greatest stability at a tRAS setting of 11 or 12. Overall, we had no difficulties at tRAS 10, but there is no performance penalty when using 11 or 12, if it improves the stability of your DDR2 memory.
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Wesley Fink - Thursday, July 8, 2004 - link
#9 - Actually the first number was copied incorrectly and has now been fixed. The tRas 11 line on p.3 now reads 5303-2344-7647.FlameDeer - Thursday, July 8, 2004 - link
Hi Wesley, nice article. :)Something to change:
At page 3, Micron PC2-4300U Table, Row tRAS 11,
Aida 32 Total should be "7697".
MIDIman - Thursday, July 8, 2004 - link
> When can we expect DDR2 for A64?http://www.anandtech.com/cpuchipsets/showdoc.aspx?...
http://www.anandtech.com/cpuchipsets/showdoc.aspx?...
mczak - Thursday, July 8, 2004 - link
Nice article, a real pity though there are no performance numbers for overclocked FSB only (i.e. FSB 258 / DDR2-"516"). There are some reasons to believe memory performance would also be quite a bit higher than with FSB200/DDR2-533...Bozo Galora - Thursday, July 8, 2004 - link
Another clear concise mem article by Prometheus.KillaKilla - Thursday, July 8, 2004 - link
When can we expect DDR2 for A64? Even thouthe they aren't so affected by lack of memory bandwidth...rjm55 - Thursday, July 8, 2004 - link
I am not usually that much into memory articles, but this is one of the best reviews I have seen on the new Intel architecture. It was surprising that even the budget DDR2 did 667. When will Intel be launching 667 as an "official" DDR2 speed?Anemone - Thursday, July 8, 2004 - link
VERY nice article - and informative on the limits that no one else is authoritatively reviewing. Thankyou and keep them coming!:)
skiboysteve - Thursday, July 8, 2004 - link
or... im blind..skiboysteve - Thursday, July 8, 2004 - link
you should mention in the benchmarks which modules are DS and SS, so people dont go ape shit over poor performance of say... GEIL..