DDR2 vs Latency

[Vric]

Hi,

I'm have looked a bit to find some real world information about the impact of the Latency on DDR2.

Is anyone have a comparison of different latency and impact on the performance in real world application.

I try to plan mu Conroe Upgrade in 2 month and I'm a bit lost in the DDR2 choice. (when you can get OCZ 2GB PC6400 5-5-5-5-15 for the same price as 1GB 4-5-4-10 kit, it's hard to choose.

Thanks for help.

[Vric]

no one have an idea ?

[kyleslater]

Ok... When you get DDR2.. Latency looks twice as large. IE the actual same latency as DDR400 2-2-2-5 would be DDR2-800 4-4-4-10

But also keep in mind the higher bandwidth actually drops the latency even lower. Now with a P4 it cannot use higher latency. I mean if I set my ram to 4-4-4-4 it works fine but 3-4-3-4 does not give me lower latency scores. AMD on the other hand will benefit from that. And Core 2 should also benefit.

Another thing. My current DDR2-667 @ 4-4-4-10 is lower latency (end result) over my old DDR-400 @ 2.5-3-3-5

I belive Everest home got me
86.3 ms latency with the DDR400
83.3 ms latecny with the DDR2-667. The best I ever got with this system was 79.4 @ 4-4-4-12 @ 745 Mhz on the ram.

[sierra_bound]

I think he's talking about latency, as in timings, though I'm not sure.

A lot of DDR2 will have SPD timings of 5-5-5 which looks awful. That's just to ensure that the memory will boot almost any board. I have a pair of Corsair 8000UL (no longer available) which have rated timings of 5-4-4-9 at 2.2v. I've never run them at Cas5. I'm pretty they will do 500MHz (DDR2-1000) at 4-3-3-4, though I haven't had a chance to test them that high yet. I have run them at close to 450 with 4-3-2-4 timings.

Personally I would look for the best 2GB kit you can find for the amount of money you want to spend. Generally the more expensive RAM will clock higher with better timings, though that's not always the case.

With Conroe, you'll probably want to run 1:1 or as close to that as possible. To get a good overclock, you'll need DDR2 that will run 400MHz at 4-4-4. There is a lot of memory available now that can do that.

[Vric]

HI

Yes, the question was about timing.. What is the impact in real world performance of CL 4 4 4 10 vs 5 5 5 15 for example.. some bench etc..

In my price range, I have the choice of 1GB with low latency, or 2gb high latency (OCZ Gold) Both PC6400.

thanks

[sierra_bound]

Here's a review (http://www.neoseeker.com/Articles/Hardware/Reviews/xms8500/) showing how timings affect performance. Some of the graphs are a little confusing because different CPU's and modules were used. What the charts clearly show is that high FSB and high memory speed are often more important than timings.

Also keep in mind that memory rated at 5-5-5 can often run at 4-4-4 or 4-5-4.

[Vric]

Thanks this is what I wanted to see.. It's not a clear cut, but look like the gain of tighter timing is about 2-4%, just like DDR and doesn't justify the 80% increase in price :p:

2GB OCZ PC6400 Gold will be.. (even if it's 5-5-5-10)

Thanks