I looked at this and the difference is negligible, less than 1% in all the benchmarks I've seen by multiple reputable sources. Back it down to 4x and there is a pretty good difference. But as for 2 1080s in SLI running in 8x the measured difference was less than 1% across the board between 8x and 16x. What that equates to? On call of duty black ops, avg FPS is identical. no difference. With other games 1 fps difference when you are talking 94 fps vs 95 fps. The results are within the margin of error for testing actually. Bottom line, the GPUs do not saturate the 7880MB/s bandwidth of PCIE 3.0 at 8X. The PCIe bandwidth has superseeded the devices capability since its inception, dont see that changing anytime soon. I can fix that 1 fps with a tiny little baby bump in clock speed! I though this one out for quite a while. Do I go with the Z170 or X99, if x99 do I go for 28 lanes or 40 lanes? I came to the conclusion that since I wont be doing any weather models for NOAA that use both the CPUs and believe it or not mostly GPUs to run the models I will see no difference other than a larger drop in my bank account balance LOL. Not like this build isn't already past the $4K mark as it stands. If I was thinking about going to 3 or 4 way SLI I may have had a different decision.

Thanks for taking the time to think about it!

Hi JustinThyme

For gaming I think you made the right choice with z170, the 6700k is clocked higher than the broadwell E cpu's and you'll likely get it to 4.8GHz with your H115i. 4 cores and 8 threads is plenty for gaming and most games benefit from the higher clock speeds.

That is one nice gaming pc you're building, with two 1080's I don't see you having problems with any games for quite a while.

The only thing I see is 64GB of 3400MHz ram could be a struggle, you'll likely have to do some voltage tweaking to get 64GB to 3400MHz.

Thanks Nate, the memory is rated for 3400Mhz and according to the manufacturer made specifically for the Z170 chipset. Seen more than one get well past 3400 but will see where I land. If they dont make at least 3400 Ill send them back from where they came! The sticks are listed on the verified vendors list for 3400.

It will be up to the cpu's Integrated Memory Controller.

If you're having problems with it when the time comes try these settings.

Extreme Tweaker tab:

CPU VCCIO voltage - 1.25v
CPU System Agent voltage - 1.25v

F10 and Enter.

If it's still giving you trouble set the Dram voltage to 1.40v

Should be a good rig! I'm jealous because I have to pay for my car before another computer but I'll enjoy following your build.

She is up an running. Takes a little finesse to get the M2 drive to work and boot. I ran it to 4.5 easy as pie then back down and the memory followed it as expected even at 1.2V when its rated for 1.35. Haven't even began to touch the ceiling of the RAM. It took going through the optimization cycle on first post though. I was blown away when I ran firestrike (just the normal one, not extreme or ultra) at stock clocks for both the CPU and GPU and got 26,400. This is gonna be fun! Only issue I have right now that came out of nowhere is the corsair link software not controlling the fans as it should. No issues for awhile until I ran unigine heaven at ultra for awhile. The fans spun up a bit (not even max speed) which was totally expected. What was not expected is after everything cooled back down the darn thing now with under 30C core temps will be so quiet you cant hear it then BAM fans rocket to max speed and sound like an F35 just did a flyby for just a second then back to whisper quiet. Lather rinse repeat. Sitting there in silent bliss just to get the crap scared out of me repeatedly. Only thing that fixes it is to put the fans at a constant speed but whats the point in having the link and software for that? May have to break out my Tbalancer from my old build if I cant sort that one out. HW monitor shows nice temps across the board. GPUs are cool as a cucumber even under full load and amazingly quiet, Don't think Ill be bothering with water cooling these. Ill post pics up when Im done, still waiting on sleeved power cables and my Samsung 960 pro.

xeromist don't feel too bad. I kinda went in the hole on this one. Well not really in the hole but had to borrow money from myself. 30 year old central heat and air had to be replaced. I nursed the heat exchanger in the gas furnace through last winter but it wasnt going to make it through another. So there went $12K for an entirely new everything with ultra efficiency. 20 Seer AC with a variable speed compressor (Id never seen that before, two stage yes, inverter driven compressor, no) Heat has a variable speed blower with a modulating gas valve so it tends to run nearly all the time at a very low fan speed and hardly any fire in the heat exchanger. Quit nice actually, no temp spikes. Well before going to far off New HVAC, paid off the wifeys car and a few other debts, New bedroom set (let the wifey go berserk on high end stuff and get what she wanted so there would be no critiquing my electronics purchases!) Nice new rig with a 4.5% loan from my 401K. Good part is Im paying myself that interest. Actually a better rate than what the market is doing right now. No long drawn out process. Just submit gimme my money, wired to my account in 3 days and automatic payroll deduction to pay it back.

I can't really complain that much. My GPU is recent so it keeps up. The CPU is a bit old but it hasn't held me back too much yet. It's just fun to build new stuff 😄