DDR 4 CL 13,14,15 - Is better CL currently worth the extra cost?

Sparktown · Nov 27, 2015

Doing a first time build with a Skylake i5-6500. The i5-6500 is locked and I only plan to use one graphics card, so I'm using an atx h-170 mobo with 4 rams lots. The build is mostly for web design/illustration, but I also plan on doing some gaming.

I'm shopping for 2x4 GB of DDR4-2133. In my understanding DDR4-2133, that is all the i5-6500 can use since it is locked (correct me if I'm wrong on this). However, there is a big price difference between CL 15, CL 14 and CL 13. Here is some of the RAM I am looking at:

G.Skill Ripjaws V Series 8GB (2 x 4GB) DDR4-2133 Memory CL 13: $39.99
Kingston HyperX Fury Black 8GB (2 x 4GB) DDR4-2133 CL 13: $54.99
Corsair Vengeance LPX 8GB (2 x 4GB) DDR4-2133 CL 13: $54.99

(Side note - Is any of this ram good?)

Does CL really matter that much? Is it worth it? I'm trying to keep this build low cost, but I would consider paying for the CL 13 is there was really noticeable/significant difference? However, I've noticed even some pretty high spec builds using DDR CL 15. What is the current 'sweet spot' for DDR4?

Please let me know soon - I'm trying to take advantage of Black Friday/Cyber Monday sales. Thanks.

Gingerbread · Nov 27, 2015

Well that is not all the speed it can used since its locked (intel have listed 2133mhz max for 6600k and i7-6700k but people are running way above 2800mhz). That said, you might look at some benchmarks of the skylake with different ram. But so far it seems that while benchmarking increases with better CL, there is pretty much no performance increase in real applications so you can stick for the lower, but still isn't the cost of 2400mhz for example pretty much $5 more?

Sparktown · Nov 27, 2015

Gingerbread :

Yeah, but 6600k and 6700k are K sku, which can be overclocked to accept ram faster than 2133. As far as I know, you cannot do that with locked (non-k) CPUs. I'm pretty sure that's how it works, but if I'm wrong let me know.

So I should just buy the CL 15 one? Do you have any benchmarks you can share? I haven't been able to find anything. Thanks.

Gingerbread · Nov 27, 2015

Well it being locked means you can't overclock it for more than its base speed, not overclock at all that is. That's why people want unlocked CPUs, so that you can overclock them to match the RAM speed, which would be the case only if you plan on getting ram higher than the CPU clock which is 3.2 which you are highly unlikely to do, meaning you can run anything up to 3200 without a problem (2800 or so should be the sweetspot). Also CL 13 vs CL14 for example is extremely minor from what I've read everywhere. But note that 2133mhz CL14 is way slower than 2400mhz CL12 (13.1 ns vs 10 ns with lower being better and lower being in favour of 2400mhz).

Sparktown · Nov 28, 2015

Gingerbread :

Okay, I did some research and I think I understand what you are saying. Please let me know if I have it:

Locked Skylakes liked the i5-6500 cannot OC to raise their CPU clock, but can still be set to accept higher than the standard 2133 DDR4 clock up to a max of that CPUs clock (3200 in case of i5-6500). I'm assuming this is done by using an XMP profile or messing with some bios settings, which would likely void the 3-year intel warranty?

Differences between 15, 14, 13 CL don't matter that much. However, there might be a more significant difference between when a better CL is combined with a better RAM clock speed. Right?

This article helped me out: http://www.silentpcreview.com/article1478-page6.html

Right now I'm thinking I'll just get some DD4-2133 CL 15 from a reputable company. I'd rather keep the 3-year intel warranty on my CPU than try for likely small speed boost. That all sound reasonable?

Gingerbread · Nov 28, 2015

You are pretty much on point but XMP profile does not void the warranty, so its better to just get faster even 2400mhz cl13 ram than an expensive 2133mhz cl 15 ram. Even better yet go for 2800mhz.

Sparktown · Nov 28, 2015

Gingerbread :

Let me just clarify. because I think I'm confusing XMP with OCing RAM. I made this mistake before.

As long as I have a Z170 motherboard, I can OC the ram (use above 2133 mhz speed) with a i5-6500 (or other locked i5 CPU). This will void the warranty on the intel CPU (although intel might not know if I don't tell them I did it). However, if I have a H170 motherboard , I won't be able to run RAM faster than 2133mhz, no matter what speed the RAM is rated at. This is all correct? I just want to make sure I have everything straight. Thanks again.

Tradesman1 · Nov 28, 2015

If the above were true then a 6700K should be able to run 4000 at stock

which is simply not true, when you look at the memory data rates supported by a mobo it's typically something like "2133, 2400 (OC), 2666 (OC), 2800 (OC).....etc, etc), that OC in there indicates that an OC of the CPU/MC (memory controller) may be required to run at those data rates. As is, suggest browsing through the forums, people with 6600K and 6700K Cpus having trouble with 2800 DRAM, 3000 DRAM - this is often becauuse they require a miinor OC of the CPU to aid the Memory controller.

With a 6500, you can prob run 2400, dependin g on your individual CPU, maybe even 2666 - I wouldn't count on 2800 or higher - possible but rather doubtful

Sparktown · Nov 28, 2015

Tradesman1 :

Good to know. But I still can OC RAM (try to run RAM clocked above 2133mhz) with an i5-6500 and Z170 mobo (but not with a H170 mobo) right?? It just voids my CPU warranty? I've gotten mixed messages from Intel about this. Please let me know. Thanks.

Tradesman1 · Nov 28, 2015

Most DRAM has been binned - i.e. if they buy 1000 chips, some asre set aside for 2133, others (slightly better go into 2400 sticks, still others, better yet end up in 2666 sticks ....etc, etc.... So yes you can normally OC DRAM up a step or so, say 2133 to 2400, and with good DRAM maybe a couple of steps (2133 to may 2666), a lot will depend on your skill with DRAM. Don't expect to get 2133 and run 2800 and better, it can be done, but isn't likely. Also the higher base data rate you start at the upward OC potential can drop, good 2800, 3000 sticks, you might be lucky to take up another notch

Sparktown · Nov 29, 2015

Tradesman1 :

Thanks, but that wasn't the answer I was looking for. It's my fault - I'm having trouble phrasing this right.

My question is: Is the I5-6500 (or any locked Skylake intel i5-CPU) prevented by the CPU from using RAM rated over 2133mhz?

In otherwords, if you give the i5-6500 ddr4-2400, will it say 'Sorry, I will only do 2133mhz because I'm locked and that is as fast as Intel let's me go" or will it say "I'm only rated for 2133mhz, but I'll do my best to get 2400 mhz - no guarantees though"?

Would I need a Z170 mobo to do this or would a H170 mobo also be able to use RAM over 2133mhz? Would I need to enable/unlock something that would void the warranty on my CPU?

I hope I explained that well enough. Please let me know. Thanks very much.

Tradesman1 · Nov 29, 2015

No, if the CPU can run 2400 or even 2666 at stock then it will, You can also help sticks on occasion by feeding them extra voltage or raising the MC voltage on a Z170. For the H170 thogh it may not allow for faster that way as the chipset is set for up through 2133

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DDR 4 CL 13,14,15 - Is better CL currently worth the extra cost?

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