So what's the sweet spot for Skylake DDR4 memory?

[LoneWolf121188]

Looks like Newegg has Ripjaw V's in stock with speeds between 2133-3000, with about $10 increments between each frequency ($100-$150) in the 2x8GB kits. So what's the sweet spot between price vs performance? With Haswell and previous chips, memory speed really didn't matter for real world performance, so I went with a 1600MHz Ripjaw kit and I've been happy with it. Is there really very much real world performance difference between the 2133MHz $100 kit and the 3000MHz $150 kit (especially if you're overclocking the cheaper kit)?

On the same note, I didn't really understand what Woomack meant in his DDR4 thread about "if you're not OCing the CPU cache, then faster memory makes no difference". Can someone explain that?

 

[EarthDog]

My thought is to get noessential than 2800mhz simply because anything below that is ddr3 speeds.

Not sure where the sweet spot is though. It was pretty cheap for 2x8gb ddr4 3k, I do know that.

As far as what woo mack said. Seems pretty straight forward... in order to get the most out of ram, overclock the cache. But who knows if this matters for normal users or just benching. I didn't see that post, so I would ask him dirextly.

 

[Woomack]

You can check tests of Ripjaws V 3000/3200 and some other kits on Skylake in my thread . Generally 3000-3200 looks best comparing price to performance. As I already said in other threads, I would get DDR4-3000 kit at lower timings like 15-15-15. Right now probably only Ripjaws V have these settings.
I wish I had some more memory kits for Skylake so I could test some more but my budget is way too limited and it's not easy to get review samples.

Regarding that cache matter. Cache clock directly affects memory performance. Simply when you set higher cache clock then memory performance will be higher but there is some point at which performance is not scalling good ( usually above 5000MHz is lower than expected, or maybe only for me ).
If you are not overclocking cache then memory performance using DDR4-3000 and DDR4-3733 kits will be almost the same. When you set higher cache frequency then you notice that memory bandwidth will go up but at 3000 it will stop scalling faster than on 3733 memory clock. However for CPU/cache clocks up to ~4.7-4.8GHz ( what is usually limit on water cooling ) you won't need much more than DDR4-3000.

When you are overclocking CPU on Skylake boards then CPU and cache has linked voltage. In this case best is to set CPU clock = cache clock for optimal performance. At clocks above 5GHz it can be hard but on air/water I doubt you will stabilize it at 5GHz or above.

 

[LoneWolf121188]

Regarding that cache matter. Cache clock directly affects memory performance. Simply when you set higher cache clock then memory performance will be higher but there is some point at which performance is not scalling good ( usually above 5000MHz is lower than expected, or maybe only for me ).
If you are not overclocking cache then memory performance using DDR4-3000 and DDR4-3733 kits will be almost the same. When you set higher cache frequency then you notice that memory bandwidth will go up but at 3000 it will stop scalling faster than on 3733 memory clock. However for CPU/cache clocks up to ~4.7-4.8GHz ( what is usually limit on water cooling ) you won't need much more than DDR4-3000.

My thought is to get noessential than 2800mhz simply because anything below that is ddr3 speeds.

I guess really what I'm asking is this: assuming a healthy overclock of 4.5GHz of both core and cache, at what point will getting higher freq RAM get you no real world performance gains? 2800? 3200? Higher? I know there's so little data out there now, I'm really just trying to get a gauge of how much I should budget for memory for my upgrade.

 

[Woomack]

In daily usage you barely see any difference in memory performance as all is already fast enough. Also fast and large CPU cache is covering any RAM delays ( if there are any ). There are programs which can use faster memory but most won't.
3000 seems good for everything and you can still overclock it higher. Most 3200 2x8GB kits won't overclock much higher.