tRAS and DDR2

OCZ rates the new PC2-4200EB at 3-2-2-8, with 8 a faster tRAS setting than we found in the DDR2 memory roundup. In the roundup we found a tRas setting of 10 was optimum for DDR2 running at 4-4-4 timings. To determine if the OCZ DDR2 ran best at a faster tRAS timing, we first ran Memtest86, a commonly used memory tool that measures memory bandwidth from a custom bootable OS.

Memtest86 showed three distinct tiers of memory bandwidth performance. The range from tRas 2 to tRas 9 showed absolutely no difference in performance. 10 to 12 showed a slight performance drop and 13 to 15, a larger performance drop. Based on Memtest86 performance, a tRAS of 8 seemed reasonable.

 OCZ PC2-4200EB - 3-2-2-tRAS
 tRAS  Memtest86 Bandwidth
2 3229
3 3229
4 3229
5 3229
6 3229
7 3229
8 3229
9 3229
10 3135
11 3135
12 3135
13 3050
14 3050
15 3050

We have seen reports on the web of claimed fantastic performance using tRAS 2 to 5 settings with this OCZ memory on the Asus P5AD2-E. This is the same board used in our new DDR2 memory test bed. So as a further check, performance tests were run varying tRAS from 2 to 15 using Everest (formerly Aida32). With Everest read/write/composite, performance was measured with 3-2-2- timings and a variable tRAS. Performance patterns in Everest were exactly the same as in Memtest86, with extremely small variations from 2 to 9 tRAS. An example is the tRAS 2 composite of 5663 compared to the tRAS 8 composite of 5686.

Our conclusion is tRAS from 2 to 9 makes no performance difference with the OCZ PC2-4200EB, so we ran all performance tests at 8. If you see enthusiasts claiming improved DDR2 performance with tRAS 2 to 5, ask for proof - as we can find no real performance difference in the 2 to 9 range with all other settings being the same.

Index Performance Comparisons
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  • dev0lution - Thursday, December 23, 2004 - link

    1GB DC Kit for $400+ and 2GB DC Kit for $800+?? I think I'll just keep the hyper-x 4300 I got for $200 less and spend more on my other components. The performance increase isn't THAT mind-blowing but the prices sure are! Reply
  • Lord Evermore - Thursday, December 23, 2004 - link

    Another sign of declining standards: the "Xenon" .13 technology? Reply
  • GTMan - Thursday, December 23, 2004 - link

    The article makes the claim that other high end memory is achieved by "hand picking" and then says that this memory is a "new breed".

    Where is the info to back this up? What is different (in terms of technology) about this RAM? Or maybe this article is only about numbers :(
    Reply
  • Carfax - Wednesday, December 22, 2004 - link

    The reason why the memory bandwidth scores are so low for DDR2-700 and 800 is obviously because the memory is bottlenecked by the FSB.

    The P4 would need to have a FSB of 1600 to take advantage of DDR2-800..
    Reply
  • Alphafox78 - Wednesday, December 22, 2004 - link

    Funny thing is that at the 700mhz speed the memory bandwith on my A64 with PC3200 is faster... Reply
  • Anemone - Tuesday, December 21, 2004 - link

    PS and I didn't even buy the matched 2gb set, just picked up 2 1gb individual sticks from Newegg.

    And at 4+ghz and sub 50c temps on air, I don't find any reason to worry about using an AMD solution...
    Reply
  • Anemone - Tuesday, December 21, 2004 - link

    I own 2 1gb sticks of this memory and while I"ve not had occasion yet to reach 811 fsb, every other timing they tested I have managed on a P5AD2-E (925XE) board. My PS is only the Antec Neopower 480 so it can also be done with a lesser PS as well.

    Expensive, yes, but given that no way would you ever see DDR1 in 1gb sticks doing this, makes it quite worth it if you need 2gb of memory in 2 sticks.

    $.02
    Reply
  • bupkus - Tuesday, December 21, 2004 - link

    Only one question...
    When will the time come that I can/should start considering DDR2 for my future AMD gaming PC?
    Reply
  • PrinceGaz - Tuesday, December 21, 2004 - link

    I just wish there were 1GB PC3200 or faster modules available for not much more than twice the price of the 512MB ones. Instead it seems 1GB DDR modules will always be overpriced and with slow timings. The Athlon 64 is crying out for fast 1GB PC3200 modules. Reply
  • MS - Tuesday, December 21, 2004 - link

    p.s. I know how to hand pick coffee beans but with memory, I would be out of my league... Reply

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