Is an X99 build with the i7-5820K worth the premium over Z170 and Skylake?

For gaming and general PC use, is the aging X99 and slowest/least PCIE lanes LGA2011 Haswell worth more than a 6700K and nice Z170 board? I want to think X99's distinct advantage lies in quad channel DDR4, but I don't know how big an advantage it would make in the real world (as in, actual, noticeable performance improvements and not a score increase in some benchmark.)

There is quite a bit of material out there from when Skylake launched and this was a hot question. Almost a year on, it appears there really isn't much to argue about in terms of performance. There are no games limited by memory at DDR4 speeds. So while my X99 can double up a Z170 read/copy score even on a bad day, it isn't going to matter for gaming or most other standard desktop activities. If you do run a professional application that is memory limited, you generally know it and it is painfully slow on lesser systems. Chasing those higher memory frequencies with Z170 has no payoff now. Hard to make predictions whether 3600 vs 3200 will matter two years on, but I would bet not.

 

Right out the box the 6700K has a clock frequency advantage. Even horrible CPUs will still make 4.5GHz, right about where most Haswell-E CPUs top out. What is 0.1-0.2GHz worth in your tasks? Probably not very much, but this the number so many people chase. I think more important on this issue is ease of overclocking. X99 can be a tricky vehicle. I've spent almost 2 years with my head inside one. Even novice users can have a 6700k at 4.5-4.6 in a few minutes and there is a possibility to stretch the clock further. If you are going to try and push for 4.6-4.7 on HW-E, you had better have a lot of money in your cooling budget and be prepared to bin multiple chips.

 

Where the X99 does have an advantage is with PCI lanes and added toys. You have to read motherboard manuals very carefully. A lot of Z170 boards that claim to support 20 lane CPUs, do not turn out as expected. Multiple GPUs will obviously be x8/x8, but a lot of people are surprised when then add on a M.2 drive and can't utilize the other x4 lanes. How these lanes are distributed and to what PCI slots is the purview of the motherboard manufacturer. Too many Z170 boards look good on paper, but reality is a little different. There are a few X99's at the bottom end who are in the same lot, but most were designed for multiple add ons. I just realized I am running 4 SSD's and an M.2 drive. I still have 6 SATA connectors left and 6 USB external ports (with 6 in use). There was a time where I was unhappy with my board and performance and was dreaming of Skylake. Even fairly recently, I considered taking my extra parts and making a Z170 system and cranking out every possible bit of speed. In the end, I realized I could never get all the playthings I have accumulated into it and I would have to give up something. I very much love the flexibility I have with X99. There isn't much I can't configure this thing to do.

 

I don't know your time frame, but what may be worth holding on for is Kaby Lake, particularly since Z170/6700k prices have not declined. As usual, we don't know how it will turn out, but it is hard to imagine it won't be an improvement on Skylake, both in terms of CPU performance and accessory options.. That is still 5 or 6 months away, so that may not be an option. I think if you are building a single GPU system and don't have the need for a half dozen add ons, the 6700K is the way to go right now. If you are an overclocker, it's a lot less heat to dissipate with higher possible clock speeds, both CPU and memory. Right now the 1080 is such an obvious single GPU choice and it covers most anyone not trying to run multiple monitors or high frame rate 4K. For casual users, I think the choice is clear as well. Z170 is a lot easier to get running fast -- certainly enough for people who don't obsess over that last 5% of performance.