Two dual-channel kits for quad-channel: optimal?

[Bouowmx]

Will using two dual-channel kits be optimal like a quad-channel kit?

High memory frequencies are typically available in only in small kits.

 

[UsandThem]

*Yes.

*Be sure to check your motherboard's QVL list, or use the memory manufacturer's "RAM Finder" tool on their websites to make sure whatever RAM you select is able to run in all four DIMM slots without issue. Sometimes, only two modules are stable depending on their speed and timings.

For example, on my motherboard's QVL, there are several kits that work fine in pairs, but failed stability testing when all four slots were occupied.

Also, just a FYI but if you are using say a z170 or z97 motherboard (basically any consumer line chipset), it won't be true quad channel. You would need a chipset like the Intel x99.

http://www.pcworld.com/article/2982...e-shocking-truth-about-their-performance.html

 

[VirtualLarry]

I've heard, but don't have absolute proof, that some memory kit mfgs, change the sub-timing subtly for greater compatibility, when using a four-stick dual- or quad-channel kit, rather than their two-stick dual-channel kits. (The logic behind that is sound - with more memory sticks, the memory controller is under more load, and may have to have some timings de-rated slightly for compatibility's sake.)

 

[Shmee]

Yes it works. My X79 system is running 2 kits of patriot DDR3 2133, and they run well in quad channel. One kit is black and one is red, and they still detected to XMP fine.

 

[Valantar]

Optimal? No. Will it work? In all probability, yes. Make sure you get kits with as close timings as possible. If the subtimings vary (which they often do between kits from different batches), adjust the faster kit to match the slower.

 

[Concillian]

Quad channel is more demanding on the memory controller. It will work, but they may or may not reach their dual channel rated speed / timing / voltage in quad config.

You need to do stability testing to ensure you are good to go. It's not the memory in this case, it's the capability of the memory controller on the CPU.

 

[BonzaiDuck]

I don't see where the OP was specific about his own hardware. If he's referring to the i7-2600, I'll say yes and absolutely, but it will be two kits running in dual-channel mode. I've done this a lot with that generation of hardware, and there's little problem.

Larry is probably spot-on and offering more specific information as "intelligence" from his sources, which he qualifies.

I'm at a crossroads myself for a 2x8 16GB kit of XMP DDR4-3200 14-14-14. I queried G.SKILL, who told me they couldn't guarantee a second kit of the same would run with the first at spec speed and/or timings. They were more optimistic about down-clocking to a 3000Mhz XMP profile. While the second kit costs about half of a 2x16 32GB kit, it offers possible slight shortcomings either way. The only means I have to guarantee 3200-14-14-14 and XMP is the 2x16GB kit. And I'll continue fretting about need, speed and techno-greed before I spend the money. At least if I said this before, it was in another thread.

 

[Bouowmx]

I don't see where the OP was specific about his own hardware. If he's referring to the i7-2600

Relevant parts of my current signature:

Dell OptiPlex 790: Intel Core i7-2600, 2×8 GB DDR3-1333 9-9-9-24-2T

The question is not about my current system, and I am not planning a computer build right now.

As for a specific, see a comparison of two memory kits: Newegg. Will two of the dual-channel kit (with higher frequency and better timings) optimally work in quad-channel like the quad-channel kit?

 

[UsandThem]

As for a specific, see a comparison of two memory kits: Newegg. Will two of the dual-channel kit (with higher frequency and better timings) work in quad-channel like the quad-channel kit?

Possibly. G Skill has a ram finder tool on their website where it will tell you what RAM they manufacture that will work properly on a particular motherboard.

If a person doesn't use RAM that is guaranteed to work properly by the manufacturer (either the motherboard or RAM manufacturer), they wouldn't know for sure until they installed it and tested it out. I call that the "plug and pray" approach.

 

[BonzaiDuck]

Possibly. G Skill has a ram finder tool on their website where it will tell you what RAM they manufacture that will work properly on a particular motherboard.

If a person doesn't use RAM that is guaranteed to work properly by the manufacturer (either the motherboard or RAM manufacturer), they wouldn't know for sure until they installed it and tested it out. I call that the "plug and pray" approach.

Yeah -- that's a good one.

Generally, from my humble and limited experience, a RAM kit may show dual-dual/quad compatibility with two chipsets. I had seen G.SKILLs that would work in either Z170 or X99. It seemed to me that none of those kits had the best timings for Z170, though. I bought the RAM at the speed I wanted and the lowest timings.

Sometimes, from the model-code common to any and all item-resellers and their description page, you can determine which models likely use same or similar "black-parts" from an alpha string in the code. As an example, I bought G.SKILL 1600's 9-9-9 XMP for my 2600K five years ago, and the code ended in the string "-GBRL." These were RipJaws; there were other Ripjaws variations -- including "X" and "Z" for which model-code ended in a different string. You could find -GBRL kits in various speed specs: 1,333, 1600, 1866. If they went higher, I never found any.

So the QVL list of the motherboard manufacturer may have shown a 1333 kit that was "GBRL" as compatible, and if the motherboard included RAM "(OC)" specs, you would see that some 1600's or 1866's would work. For those DDR3 kits especially, we - I -- found that you could OC the 1600's to 1866 by loosening the first three timings by 1, and probably the fourth timing by 6.

Sometimes, the RAM-maker -- like G.SKILL -- will have a configurator which shows they only tested certain board models and that yours, which is part of the same model-line, isn't included. Well -- look at the specs to the next higher or lower model. Or both. If they turn up certain models that fill your bill and float your boat for speed and timings, using those models may be fairly certain of success.

If there's any "Plug-and-Pray" after that, you have 30 days depending on where you bought them, but with that kind of investigation to turn up a model you would like for your board, not likely to happen.

Put it another way. If your X99 chipset is implicitly compatible with a 2x kit that otherwise operates as dual-channel, you should be able to use two kits and use them in quad-channel configuration.

 

[Shmee]

X99 may have trouble running those kits at rated speed, especially in Quad channel. DDR4 3200 and greater has very diminishing returns on X99, and often won't run at higher speeds anyways. Most of the super fast DDR4 is meant for Z170 or Z270.