4 Dimm Board, Dual Channel (Asus Z170a), 2 x (2x8) sets of exact same ram. Will XMP adjust?

[BigJohnnyTwoToes]

So I am about to build a new PC. It will be i7-6700k with asus z170a MOBO. I just bought G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-3200 Memory. After doing so, I decided i wanted to have 32gb and bought the exact same pair from the same vendor again (less than 24hrs later). I understand that it is best to try and get a kit of ram, but there are some determining factors i am confused about. This is a multi-part question really:

1. Does it matter if I use 2 pairs or a pack of 4 if the board is dual channel anyway?

2. Can the XMP profiles be activated for each pair seperately, or will i have to hope that they match and that 1 profile works.

3. If i have to get a new kit instead, Is 2x16 noticeably faster than 4x8?

BTW another arguement for 2x16 vs 4x8 is that youll have 2 more slots to upgrade later, but that doesn't make sense if your supposed to buy your ram as a kit instead of 2 pairs lol.

4. LAST PART: Do i have to get ram on the approved list of the motherboard? It seems there really are only 4x8 3200mhz kits on there, so if 2x16 is faster, id have to go down to 3000 according to them. (i know not a big deal, just saying)

Ive just seen a lot of conflicting information.

THANKS!

 

[Luminary]

1) Yes, there is a small chance they still won't work together. We REALLY do suggest buying all your RAM in a single pack. Section 6 of the Tom's article "The Most Common DDR DRAM Myths Debunked" goes into the specifics of why in detail.

2) I'm almost certain they share the same profile, but you'll want verification on this one since I can't say definitively.

3) The asus z170a doesn't have quad in-line support, so I don't think you'll see too much difference between a 2 and 4 pack.

"BTW another arguement for 2x16 vs 4x8 is that youll have 2 more slots to upgrade later, but that doesn't make sense if your supposed to buy your ram as a kit instead of 2 pairs"

You hit the nail on the head here. Keeping a few slots open for mixing RAM later isn't something we suggest as 'best practice'

4) Motherboard approved RAM lists are not comprehensive. Any DDR4 Memory that fits within your Motherboard Specs should work fine (your CPU can support even the fastest models) :

--4 x DIMM
--Max. 64GB
--DDR4 3400(O.C.)/3333(O.C.)/3200(O.C.)/3100(O.C.)/3000(O.C.)/2933(O.C.)/2800(O.C.)/2666(O.C.)/2600(O.C.)/2400(O.C.)/2133(O.C.) MHz Non-ECC, Un-buffered Memory
--Dual Channel Memory Architecture
--Supports Intel® Extreme Memory Profile (XMP)

 

[BigJohnnyTwoToes]

1) Yes, there is a small chance they still won't work together. We REALLY do suggest buying all your RAM in a single pack. Section 6 of the Tom's article "The Most Common DDR DRAM Myths Debunked" goes into the specifics of why in detail.

2) I'm almost certain they share the same profile, but you'll want verification on this one since I can't say definitively.

3) The asus z170a doesn't have quad in-line support, so I don't think you'll see too much difference between a 2 and 4 pack.

"BTW another arguement for 2x16 vs 4x8 is that youll have 2 more slots to upgrade later, but that doesn't make sense if your supposed to buy your ram as a kit instead of 2 pairs"

You hit the nail on the head here. Keeping a few slots open for mixing RAM later isn't something we suggest as 'best practice'

4) Motherboard approved RAM lists are not comprehensive. Any DDR4 Memory that fits within your Motherboard Specs should work fine (your CPU can support even the fastest models) :

--4 x DIMM
--Max. 64GB
--DDR4 3400(O.C.)/3333(O.C.)/3200(O.C.)/3100(O.C.)/3000(O.C.)/2933(O.C.)/2800(O.C.)/2666(O.C.)/2600(O.C.)/2400(O.C.)/2133(O.C.) MHz Non-ECC, Un-buffered Memory
--Dual Channel Memory Architecture
--Supports Intel® Extreme Memory Profile (XMP)

Thank you very much for the quick and comprehensive response! So in your opinion, based on what we just discussed, if i want 32gb of ram I should get a kit of 2x16 or 4x8, whichever is cheaper basically. Would you also agree that the difference between 3200 and 2666 is pretty unnoticeable?

 

[Luminary]

No problem, happy to help.

Yes, I'd personally go with whichever 32GB module is cheaper.

Ripjaws V is a very good model to look at. I know Tradesman also particularly likes one other type of RAM for DDR4 after his testing as well, so he might chime in with another recommendation. I just can't think of the model off-hand.

And you're correct, you really won't see much real-world performance difference between 3200 and 2666 in everyday use. You would have to be running enormously RAM intensive video rendering or 4k gaming activities to see any type of difference between the two.

 

[jossrik]

If I remember correctly, the 2x16Gb is ever so slightly faster than the 4x8Gb choice, also, the 2x16Gb is easier on the memory controller, and your CPU will run again, ever so slightly, cooler. The differences are small enough that either choice is good, and unless you're big on benchies, there's no appreciable difference.

 

[Tradesman1]

Preferable for 32GB will be a 2x16GB (and not so you can add in the future - as there are no guarantees when adding/mixing packages of DRAM), but that 2 sticks of DRAM is less stress on the MC (memory controller which resides in the CPU. The additional stress of 4 sticks over 2 can have an effect on OC capabilities. Do you need to get DRAM off the QVL, No, the QVL is but a small sampling of available DDR that they have had available and the time to test with

 

[BigJohnnyTwoToes]

If I remember correctly, the 2x16Gb is ever so slightly faster than the 4x8Gb choice, also, the 2x16Gb is easier on the memory controller, and your CPU will run again, ever so slightly, cooler. The differences are small enough that either choice is good, and unless you're big on benchies, there's no appreciable difference.

Yes i have seen this all over the forums, but i have yet to see someone quantify the real life impact. Like how much faster, how much more stress on the memory controller, and how much cooler? I am about get the corsair LED dimms and 4 looks so much cooler lol, i want to know the TRUE impact of runnning 4x8 instead of 2x16?!!

 

[Tradesman1]

There is no way to quantify exactly as it all depend s on your individual CPU, each 6700K is an individual entity, some OC much better than others, some have stronger or weaker MCs that the norm, etc (silicon lottery). You can find some general insights about DRAM in my FAQs and Fiction articles, links to both here:

http://www.tomshardware.com/answers/id-2741495/ddr3-faqs-fiction.html