z170 vs x99 CPU's - gaming performance.

[Perfect_Chaos]

Had a bit of a chat with one of the guys over at Digital Foundry through E-mail, because i was considering putting together a separate 6700k system.

This is a response when i asked about the RAM they used in the z97 setup vs the 6700k because it was never mentioned, and overall performance of the z170 setup in their 6700k review, mainly asking about the minimum frame rates.

We used 1866MHz RAM in the 4790K system at the time if I recall and back then, we weren't aware of how crucial RAM was. Based on the subsequent tests we've done with Skylake (eg Core i5 6500 review) I think the faster results from 6700K are a combination of higher memory bandwidth and IPC.

It is highly unlikely that you will have memory bandwidth constriction issues with the 5820K assuming you are using four sticks of RAM and I'd stick with that. Virtually all modern games are now aware of at least eight threads. The Division works with 12!

I tested my 5960X with six cores active at 4.4GHz and results were in line with 6700K suggesting a multi GPU setup is required to differentiate them.

For now I'd stick with 5820K!

And when asked about the x99 system he had run tests with..

I can't recall what the 5960X results were, only that they were so similar that I quickly realised I'd need a multi-GPU set-up to spot any kind of tangible difference. I'd *love* to test a 5820K - I don't have one. I'm actually going to do a series of builds that we'll regularly update and multi-GPU is one of them - for this I've pencilled in 5820K which I guess I'll end up buying.

But the way things are going by the time I get around to it, the 6800K will be out. That may actually be a better upgrade for you as I'm pretty sure Broadwell-E will slot into an X99 board.

My gut feeling is an overclocked 5820K will best the 6700K. My thinking is this:

* Overclocked i5 can match i7 performance as an average, but lowest frame-rates never match (ie stutter)
* Six cores offers more threads and more power
* Virtually every game these days uses eight threads minimum

I did notice an outlier though. Weirdly, Assassin's Creed Unity runs slower on 5960X than it does on 4790K (with 1600MHz RAM!). I noticed this during the Titan X review and never quite got my head around it: http://postimg.org/image/usom8329z/

So the 4790k cannot really be used as a substitute to compare a 5820k (or any x99 chip) vs the 6700k in their review, the higher performance is due to DDR4 as well as the extra IPC. So moving from z97 to x99 has the memory advantage in its favor.

Thought some may find it interesting anyway. And i already know some say the difference is small - but with the DDR4 and higher clocked memory on x99 the difference between it and Skylake is even smaller it seems, for the most part.

Also as a last bit:

Got quite an interesting piece coming up - can the 2500K still hack it? Basically, 2500K at 4.6GHz with 2133MHz RAM is equivalent to stock i5 6500 3.2GHz with 2666MHz RAM. Fairly easy to hit CPU limits on the 2500K these days - even with GTX 970.