DDR RAM timings question...

Discussion relating to Socket 7 hardware.
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KenB
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DDR RAM timings question...

Post by KenB »

I know DDR is not used on K6 platforms, but the question/answer might be pertinent even to SDRAM.

Anyway, my question is on the following choices of RAM timings. I'm unsure which of these specs would prove to be faster (theoretically, at least) on a system...
  • CL - tRCD - tRP - tRAS

    2.5 - 3 - 3 - 6

    2.5 - 6 - 3 - 3

    2 - 3 - 3 - 6
I'm unsure if any one of the specs take precedence over the others. I know CAS is often listed. Does this mean it is the most important one to consider? That would make 2-3-3-6 the fastest, if so. But if the other specs are important or more important, then which?

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Uranium235
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Post by Uranium235 »

Rule of thumb for any RAM - lower numbers are faster. So 2-3-3-6 would be fastest with the lowest CAS rating taking precedence. Hope that helps. ;)

KenB
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Post by KenB »

So CAS latency is the most important of the specs then? I guess it makes sense, since that's the one spec always mentioned.

Thank you.

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swaaye
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Post by swaaye »

The least important is the third timing, RAS Precharge. The CAS and RAS-to-CAS are both rather influential.

You can frequently configure the fourth you have listed, RAS timing. That one usually doesn't do much either, like RP. But on nForce mobos you can actually gain performance by running it up around 11 @ 400 FSB (and somewhat lower as you decrease FSB). It's a strange quirk to nForce 1/2.

1BadMoJoe
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Post by 1BadMoJoe »

I concur with Uranium235 2-3-3-6 would yeild slightly better results.
I did noticed 2.5 - 6 - 3 - 3 sould look like this 2.5-3-3-6 some memory manufactures swap tRCD and tRAS, I would find it hard to beleive tRAS would equal so mush less than tRCD and tRP combined.

tRCD + tRP should be close to = tRAS

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