6700k Memory Scaling on Z170

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I have a bunch of questions here and will probably be all over the place as I'm researching...

I'm trying to figure out the sweet spot for memory speed for a Skylake build with the i7-6700k. I didn't think the i7-6700k would benefit at all from a higher memory speed than rated (2133Mhz) but it looks like it does make a difference especially if overclocking. From what I've read it looks like for Skylake you should aim for 3600+

For gaming there really isn't much of a reason for more then 16GB of ram so it would make sense to me to go with a higher frequency kit of 8-16GB instead of a lower frequency kit of 32GB+. Also there doesn't seem to be much of a difference in ram speed for gaming besides higher minimum fps and possibly a marginally higher max fps. Where higher speed does seem to make the biggest difference is in read/write memory bandwidth. So what's the importance of memory bandwidth exactly?

On Intel's website it says the 6700k has a max memory bandwidth of 32.1GB/s. I'm fairly novice to overclocking but I'm guessing the your memory bandwidth goes up with a higher clock rate and cache size?

"With the slowest DDR4-2133 dual channel memory kit on the market we were just shy of 32,000 MB/s of read/write memory bandwidth and by the time we got up to DDR4-3866 we were running over 50,000 MB/s! The write memory bandwidth went from 31,923 MB/s to 56,467 MB/s, which is a massive 24,544 MB/s or 76.9% increase in the effective write bandwidth." DDR4 Memory Scaling on Intel Z170 - Finding The Best DDR4 Memory Kit Speed - Page 3 of 6 - Legit Reviews

So far I've narrowed down my search to these kits and trying to decide the best performance and value.

G.SKILL Ripjaws V Series 32GB (2 x 16GB) 288-Pin DDR4 SDRAM DDR4 2400 (PC4 19200) Intel Z170 Platform / Intel X99 Platform Desktop Memory Model F4-2400C15D-32GVR - Newegg.com $120 for 32GB, $240 for 64GB
G.SKILL Ripjaws V Series 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3000 (PC4 24000) Intel Z170 Platform / Intel X99 Platform Desktop Memory Model F4-3000C15D-16GVRB - Newegg.com $70 for 16GB, $140 for 32GB
G.SKILL Ripjaws V Series 16GB (4 x 4GB) 288-Pin DDR4 SDRAM DDR4 3000 (PC4 24000) Intel Z170 Platform / Intel X99 Platform Desktop Memory Model F4-3000C15Q-16GVR - Newegg.com $90 for 16GB
G.SKILL Ripjaws V Series 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 3200 (PC4 25600) Desktop Memory Model F4-3200C14D-16GVR - Newegg.com $100 for 16GB, $200 for 32GB
G.SKILL Ripjaws V Series 8GB (2 x 4GB) 288-Pin DDR4 SDRAM DDR4 3466 (PC4 27700) Intel Z170 Platform Desktop Memory Model F4-3466C16D-8GVK - Newegg.com $51 for 8GB, $102 for 16GB
G.SKILL Ripjaws V Series 16GB (4 x 4GB) 288-Pin DDR4 SDRAM DDR4 3466 (PC4 27700) Intel Z170 Platform Desktop Memory Model F4-3466C16Q-16GVK - Newegg.com $109 for 16GB
G.SKILL TridentZ Series 8GB (2 x 4GB) 288-Pin DDR4 SDRAM DDR4 3600 (PC4 28800) Intel Z170 Platform Desktop Memory Model F4-3600C17D-8GTZ - Newegg.com $76 for 8GB, $152 for 16GB
G.SKILL TridentZ Series 16GB (4 x 4GB) 288-Pin DDR4 SDRAM DDR4 3866 (PC4 30900) Intel Z170 Platform Desktop Memory Model F4-3866C18Q-16GTZ - Newegg.com $210 for 16GB
G.SKILL Ripjaws V Series 8GB (2 x 4GB) 288-Pin DDR4 SDRAM DDR4 3866 (PC4 30900) Intel Z170 Platform Desktop Memory Model F4-3866C18D-8GVK - Newegg.com $90 for 8GB, $180 for 16GB
G.SKILL TridentZ Series 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 4000 (PC4 32000) Intel Z170 Platform Desktop Memory Model F4-4000C19D-16GTZ - Newegg.com $190 for 16GB, $380 for 32GB

What if I were to buy a higher frequency memory kit and down clock for with tighter timings and a CL1 instead of CL2?

Would I get better performance if I populate all 4 dims instead of 2?
EDIT: It looks like having all 4 dimms populated can put more stress of the memory controller and make it difficult if you're trying to overclock.

Some information on memory speed/timings
Memory - RAM Performance: Speed vs. CAS latency | Crucial.com
DDR4 Memory Scaling on Intel Z170 - Finding The Best DDR4 Memory Kit Speed - Legit Reviews




"Optimize your system by installing as much memory as possible, using the latest memory technology, and choosing modules with as much speed as is cost-effective and/or relevant for the applications you're using."
 
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Nenu

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I have a bunch of questions here and will probably be all over the place as I'm researching...

I'm trying to figure out the sweet spot for memory speed for a Skylake build with the i7-6700k.
...

HUGE post, almost no detail.
Do you intend to fry chips with your PC?
 

Nenu

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Yeah that was a bit cryptic.
What are you using your PC for?
Hard to provide answers without knowing.
 
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I just want to make a decent gaming machine and I'm one of those who like to get the most out of their money by overclocking.

So I'm looking to purchase this motherboard GIGABYTE G1 Gaming GA-Z170X-Gaming 5 (rev. 1.0) LGA 1151 Intel Z170 HDMI SATA 6Gb/s USB 3.1 USB 3.0 ATX Intel Motherboard - Newegg.comand it says it has a max ram speed of DDR4 3466*(*O.C.). I want to run the fastest ram possible this board will support and was wondering if I were to purchase a 4000MHz kit if I were to underclock it to run at 3466 frequency with tighter timings would it be better performance vs buying a 3400MHz or 3466MHz ram kit?

If a motherboard says 3466* O.C. will it easily run a module already rated at that frequency?
 
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limitedaccess

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You need to go to the manufactures page's memory support list to see what exact case they qualified that for, such as voltage, type of DIMM, numbers of DIMMs, etc. Alternatively you can see what the memory manufacturer qualified for.

What speed you can actually achieve will be dependent on what the memory itself is capable of, the CPUs IMC, the motherboard (eg. traces, layers, etc.) and of course lottery (or manufacturing variance).

In terms of how much memory would benefit gaming, that would end up depending on work load and how your measuring performance. For instance Fallout 4 in situations with a lot of traversal or objects and looking at minimum fps (worst case) you'd have a lot of benefit. Whereas something like Rise of the Tomb Raiders built in benchmark's avg fps would be the opposite.

However from what I know of >3200 really starts to hammer into the diminishing returns category. Beyond that you might just want to factor in stability and ease of use (eg. just plug and play without having to test and tweak) for just a daily use gaming system if not monetary costs.

Also we are still relatively early in DDR4s life time. Don't be surprised if the quality of memory gets much improved during your systems life time.
 
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dasa

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higher ram speeds help cpu performance which is why many gpu bottnlecked ram performance reviews show next to no improvement

there is some cpu limited tests a few posts down some that show higher ram clocks meaning as much as 400mhz higher cpu oc with older cpu
Memory Scaling Reviews: Vast Conspiracy? - AnandTech Forums

cheaper mb with thin pcb can struggle with higher speed ram kits especially when combined with larger quantity of ram over 2x4g
these days you really want 2x8g
with that gb mb you will be lucky to run 2x8g much over 3000mhz 15-15-15 without a fair bit of extra vtt

you can get ripjaws v 3000 15-16-16 for $64 which would probably be the best value
if you want to try tweak some more out of it these kits have good samsung chips
ripjaws v 3200 14-14-14 $100
after this the price continues to go up quickly and the timings typically get so much worse that the latency doesnt improve much at higher frequencies
 

Raendor

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I was always wondering, does running high speed memory require any increase of core voltage for cpu with OC comparing to running memory on stock? Or how the system performs with high speed memory depends only on motherboard and memory itself independent of what OC and core voltage you have on your cpu? I'm asking because I have 6700k on asus z170 pro gaming (claiming to support memory up to 3400) and a kit of 2x8 G.skill ripjaws V 2800 MHz 15-16-16-35 1.2 that I could run well at 3200 MHz 16-18-18-38 1.35 passing memtest with no errors and having no problem in games, but still once in a while (weeks could pass) the system was showing OC fail at boot. However it never failed to boot with xmp or being set to 3000 MHz 15-16-16-35 1.35.
 

Nenu

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I was always wondering, does running high speed memory require any increase of core voltage for cpu with OC comparing to running memory on stock? Or how the system performs with high speed memory depends only on motherboard and memory itself independent of what OC and core voltage you have on your cpu? I'm asking because I have 6700k on asus z170 pro gaming (claiming to support memory up to 3400) and a kit of 2x8 G.skill ripjaws V 2800 MHz 15-16-16-35 1.2 that I could run well at 3200 MHz 16-18-18-38 1.35 passing memtest with no errors and having no problem in games, but still once in a while (weeks could pass) the system was showing OC fail at boot. However it never failed to boot with xmp or being set to 3000 MHz 15-16-16-35 1.35.
For your particular issue, trial and error will find you the cure.
Lucky you though getting GSkill, I bought early and was very restricted on choice. Had to get Corsair LPX 3000MHz and had a nightmare getting it to run at rated speed. With an ASrock and MSI board it was only rock stable at much lesser speed (cant quite remember now, 2800MHZ or less) no matter what I did.
I ended up buying a high end Asus board despite avoiding them due to customer service and this actually fixed it. but I cant overclock even slightly, hmph.

You probably know the score.
One by one try reducing your uncore (CPU cache) speed, slightly higher vcore, slightly higher Vram, increase CAS...
If your Command Rate is set to 1, try 2.

The System Agent and VCCIO voltages are useful for stabilising overclocked ram, tweak them both up a bit.
Find out what voltage they reach when the ram is under heavy use, the default voltage might not be static when on auto.
Then use a voltage slightly higher, work from there.

Also see if your motherboard BIOS has some presets for your ram, many have built in lists of different memory types or specific memory modules. Try a faster version of your ram settings and optimise if it fails to work. This may set up other settings/ram timings that are more of a pita to get right.

You may end up needing to tweak more than one setting, it can be a pig to sort out occasional issues.
Good luck, nice ram.
 

Raendor

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For your particular issue, trial and error will find you the cure.
Lucky you though getting GSkill, I bought early and was very restricted on choice. Had to get Corsair LPX 3000MHz and had a nightmare getting it to run at rated speed. With an ASrock and MSI board it was only rock stable at much lesser speed (cant quite remember now, 2800MHZ or less) no matter what I did.
I ended up buying a high end Asus board despite avoiding them due to customer service and this actually fixed it. but I cant overclock even slightly, hmph.

You probably know the score.
One by one try reducing your uncore (CPU cache) speed, slightly higher vcore, slightly higher Vram, increase CAS...
If your Command Rate is set to 1, try 2.

The System Agent and VCCIO voltages are useful for stabilising overclocked ram, tweak them both up a bit.
Find out what voltage they reach when the ram is under heavy use, the default voltage might not be static when on auto.
Then use a voltage slightly higher, work from there.

Also see if your motherboard BIOS has some presets for your ram, many have built in lists of different memory types or specific memory modules. Try a faster version of your ram settings and optimise if it fails to work. This may set up other settings/ram timings that are more of a pita to get right.

You may end up needing to tweak more than one setting, it can be a pig to sort out occasional issues.
Good luck, nice ram.

Thanks. I got this Ram back in October 2015 when it was around $105 (look at how less it costs now lol, between $60-70) when I was also limited in choice. Otherwise would've gotten 3000 or 3200 sticks from the start, but can't complain since I had no issues with 2800 xmp and as I said, I can run them at 3000 with same timings only with voltage bump to what any other 3000-3200 sticks use and even 3200 works just fine within the system and gaming tasks (I'm trying to achieve 3200 100% stability on load because of F4 lol).
My vccio and system agent volatges are on auto and are about 1.15ish and 1.2ish so around the values recommended for OCed memory so I never bothered with tweaking them. Is it better to set static values for them?

Btw, saw numerous compaints on asus and corsair combo. it's like they're incompatible. Ridiculous!
 

Nenu

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It has to be worth a try.
VCCIO max is 1.2V.
VSystem Agent max is 1.25V but be aware that too much or too little can cause instability so go very slowly changing this.
 

dasa

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i was just reading this earlier you may find it useful
[GUIDE] Skylake Memory Timings on Asus Motherboards ! - HWBOT forum

from what i remember of reading through the thread this may have been the reason for some getting random instability with higher oc
ISSUE #5: BAD RTL Training
Sometimes the memory training is missed and you can see big difference in RTL/IO,for example instead of 50/51/7/6 you will have 58/51/14/6 and similar.This WILL hurt the performance a lot in 32M and XTU too,It is always best when finding proper RTL/IOL combo to manually lock them by overriding AUTO so you will have same values every time.

there is also a general oc guide here
ROG Maximus VIII - HWBOT forum

i have just purchased a 6700k asus viii gene g.skill v 2x8g 3200c14 myself
 
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Archmage

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Note: I do not own a Skylake system. This is just what I've read about z170 / DDR4.

I do believe that people tend to undervalue memory speed, and that it does come in handy under certain scenarios: Memory Scaling Reviews: Vast Conspiracy? - AnandTech Forums - that's a lot of reading...

I believe the G.skill 8GB modules (so 2x8GB or 4x8GB are your options) DDR4 3000/3200 rated at 14-14-14 = Samsung B-die = same as the high performance modules, and will likely match their clocks and timings (often beyond ddr-4000 cl17-19 at default 1.35v). How close you can get to DDR4-4000 seems to be largely dependent upon motherboard.

Apply slightly more voltage, like 1.45v, and you may get something like 3600 at 15-15-15. I've certainly seen 3600 at 14-14-14 at 1.55v, but that may have been for the 16GB modules, which actually don't generally go beyond 3600 anyway.

Of course the overclockers are experimenting with all voltages up to 2.2v - not sure about longevity there, good lord.

That was $100 per 16GB (2x8GB) for the Ripjaws 3200, and TridentZ 3000 at 14-14-14-34 1.35v - Newegg.

There isn't much point spending beyond that for usable performance.

Edit: K, I found one of Woomack's threads: G.Skill Trident Z 2x8GB DDR4-3000 CL14 - F4-3000C14D-16GTZ | Overclockers Forums - he likes to test memory...

Edit 2, the next day: I didn't realize dasa had already posted much of the same information... D'oh...
 
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I've since decided to go with the ASRock Fatal1ty Z170 Professional Gaming i7 and made a new memory list.

Core i5-6600K 3.5GHz Quad-Core - Skylake Build #2 - b60khansen's Saved Part List - PCPartPicker

These are the kits I've found under $100. The G.SKILL Ripjaws V Series 16GB (2 x 8) (14-14-14-24) DDR4 3200 $100 with those nice timings looks like a good choice to me. What would you guys choose?



  • G.SKILL Ripjaws V Series 8GB (2 x 4GB) (15-15-15-35) DDR4 2400 $38
  • G.SKILL Ripjaws V Series 8GB (2 x 4GB) (16-16-16-36) DDR4 3200 $44
  • G.SKILL Ripjaws V Series 8GB (2 x 4GB) (15-15-15-35) DDR4 3000 $46
  • G.SKILL TridentZ Series 8GB (2 x 4GB) (16-16-16-36) DDR4 3200 $54
  • G.SKILL Ripjaws V Series 8GB (2 x 4GB) (17-18-18-38) DDR4 3600 $59
  • G.SKILL Ripjaws V Series 16GB (2 x 8GB) (15-15-15-35) DDR4 2400 $60
  • G.SKILL Ripjaws V Series 16GB (2 x 8GB) (15-16-16-35) DDR4 3000 $64
  • G.SKILL Trident Z Series 8 GB (2 x 4GB) (17-18-18-38) DDR4 3600 $76
  • G.SKILL Ripjaws V Series 16GB (2 x 8GB) (16-18-18-38) DDR4 3200 $79
  • G.SKILL Ripjaws V Series 16GB (2 x 8GB) (15-15-15-35) DDR4 3000 $80
  • G.SKILL Ripjaws V Series 16GB (2 x 8GB) (14-14-14-34) DDR4 3000 $90
  • G.SKILL TridentZ Series 16GB (2 x 8GB) (16-16-16-36) DDR4 3200 $90
  • G.SKILL Ripjaws V Series 16GB (2 x 8GB) (16-18-18-38) DDR4 3400 $95
  • G.SKILL Ripjaws V Series 16GB (2 x 8) (14-14-14-24) DDR4 3200 $100
 
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Nenu

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I would get the fastest speed with the tightest timings considering how little extra it costs.
(faster MHz means more than a few drops in latency so get the fastest if latency isnt crap)
From early tests 2800MHz is the minimum to avoid wasting your expensive CPUs capability with not much benefit moving beyond 3200MHz.

I bought 16GB 3000MHz because of this and that cost £124. Removing tax and approx $1.5 = £1 at the time, that makes it $155.
Prices are much cheaper and so close now, get the best 16GB kit.
 

chaos4u

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thesmokingman

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