Frequency, Latency, and Motherboard Compatibility

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poochiepiano

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Nov 1, 2010
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Right now Newegg is selling two kits of G.skill 2x8GB at different speeds for around the same price. ($4 difference)

One is at 2400 Mhz with 11-13-13-31 timings
The other 1866 Mhz with 9-10-9-28 timings

1.) As advertised, what is the difference?
2.) Some of the reviews for 2400 Mhz said that their mobo set it to 2400 Mhz but with 9-9-9-24 timings automatically and it worked fine. Which... would pretty much be the bomb if that happened. Is there anything to worry about with that, because I'm fine with the advertised timings, probably.
3.) I am running an i5-4690k on an ASrock z97 Extreme6. Is it even going to support 2400 MHz? It is one of the frequencies listed in their memory specs, but with an "(OC)" at the end. Does that mean XMP won't automatically put it at 2400 and I'll need to do it manually? 1866 also has "(OC)" after it.

Thanks!
 
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thx1138v2

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The "(OC)" means the mobo is not guaranteed to work at that rate. It might and it might not. A lot will depend on the specific RAM stick you get. The RAM sticks vary batch to batch and they can vary in the same batch.

They will probably have a better chance of working if those sticks are in the Qualified Vendors List (QVL) which you can find on the support page for that particular mobo.
 
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poochiepiano

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Oh, I never knew about this. Well, the specific model number is not on there, but there are very similar models with the same frequency from the same manufacturer that are. I think that should be okay, or at least, enough for me to be willing to take a risk on. Thanks, thx1138v2.

I guess then my questions get back to technical questions about memory in general:
1.) What differences in performance can I expect (aka which one should I get)
2.) I know RAM you basically fiddle with until it is stable, but is 2400Mhz/9-9-9-24/1.65V within somewhat "safe" parameters?
 
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Tradesman1

Tradesman1

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The 'OC' means that CPU and/or MC (memory controller) may well require an OC to run at that data rate. Many non-K Haswell CPUs will run 1866 and possibly even 2133 with the CPU at stock settings. However some will require an OC to run 2133 and higher, requiring a K model CPU. The 2400 data rate offers higher bandwidth and thus better overall system performance. Can get some idea of performance differentials in my article here:

http://www.tomshardware.com/reviews/dram-benchmark-fluctuations,4080.html
 
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poochiepiano

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Thanks for the answer, Tradesman1. Okay, so since I have a 4690K, the ability is there, at least. From your article, it sounded like XMP was all it took to take the RAM to 2400 MHz. From your explanation and Jim Reece's article on DRAM myths a while back, It sounds like a CPU overclock could potentially be necessary to help the CPU manage 2400 MHz sticks but at the same time, it also sounds like lower clock speeds would make only a marginal difference. I'm on the stock CPU cooler so I don't want to get crazy with overclocking the CPU.

If I understand RAM correctly, since speed and timings are connected, if I have the same experience with reviewers on Newegg and the timings are set to 9-9-9-24 and 2400 Mhz, then the 2400 kit would be better. Is there any downside or instability with having that timing? Otherwise, the higher latency would probably just balance out the higher bandwidth (according to some LinusTips video I just watched)? I might get the 2400 anyways since it's only a $4 difference but yeah, any thoughts?

Edit: Oh, apparently you ARE Jim Reece, haha. Well thanks for all the articles on RAM :)
 
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