RAM: Speed VS CAS Latency?

[chris3488]

I am currently looking for 16gb (4x4) ram for my Z170 gaming-only PC. What type of ram should I get? Ram with the highest speed? High or low CAS latency? Or something in the middle? What is best? Does speed and CAS latency even matter when RAM is used for gaming? So many questions! Thanks!

 

[tonystark_a]

higher speed with lower cas is best

 

[Eddyke1]

IDoes speed and CAS latency even matter when RAM is used for gaming? So many questions! Thanks!

I know that iff you play open world games online you will use alot of RAM,

 

[BadActor]

Many games and programs respond well to higher frequency RAM. As said above, look for the highest speed RAM with the lowest case latency that fits your budget.

http://www.crucial.com/usa/en/memory-performance-speed-latency

 

[chris3488]

Is this RAM good: http://www.corsair.com/en-us/dominator-platinum-series-16gb-4-x-4gb-ddr4-dram-2133mhz-c10-memory-kit-cmd16gx4m4b2133c10

Or is the speed too low/CAS latency to high?

 

[turkey3_scratch]

You can't compare latency directly among different-frequency memory, you need to take into account both because it's the frequency / latency ratio that is most important. CAS latency is how much time it takes the RAM to initially have requested data reach the CPU. It is measured in cycles, or hertz.

Take 1 / (frequency / 2) to get the time for one cycle of the memory. Then, multiply it by the CAS latency, and whichever has a smaller value has a better latency in seconds.

With that said, higher frequency is also better than lower frequency. RAM is become more relevant.

 

[rhysiam]

For a start, for your Z170 board you want 2x8GB RAM, not 4x4. Z170 will only use 2 channels, so no point using extra DIMMs. A 2x8 Kit will give you identical performance, (potentially) less stability issues, less stress on the memory controller and easier future upgrades.

Second thing I would say is that expensive RAM is one of the worst places to spend your budget for a gaming build. I would honestly look at the price of a stock 2133Mhz kit. Then you'll usually find a kit that offers slightly higher frequency and/or lower latency for about the same of a few dollars extra. Any money spent on top of that would be much better invested into your GPU or CPU.

 

[BadActor]

I generally look for 2666 to 3200 speed RAM with the lowest latency for a gaming system. Beyond these speeds the price rises dramatically and the extra performance isn't worth it. Use filters on PCPartPicker to help you narrow your search down.

https://pcpartpicker.com/parts/memory/#s=402666,403000,403200&Z=16384002&sort=a10&page=1

 

[tonystark_a]

Is this RAM good: http://www.corsair.com/en-us/dominator-platinum-series-16gb-4-x-4gb-ddr4-dram-2133mhz-c10-memory-kit-cmd16gx4m4b2133c10

Or is the speed too low/CAS latency to high?

this good cas for that speed

 

[rhysiam]

Just in case you don't want to take my word for it, look at the recent Tom's memory review: http://www.tomshardware.com/reviews/gskill-trident-z-32gb-ddr4-3000-memory,4441-2.html

High end RAM is technically much faster in the memory specific benchmarks (no surprise there), but look at the "real world benchmarks" section. There's basically no measurable difference between a kit at 3400mhz or higher and stock 2133mhz.

 

[Archaic59]

Is this RAM good: http://www.corsair.com/en-us/dominator-platinum-series-16gb-4-x-4gb-ddr4-dram-2133mhz-c10-memory-kit-cmd16gx4m4b2133c10

Or is the speed too low/CAS latency to high?

Yes, it's great memory but not worth the price. Try this-

http://pcpartpicker.com/part/corsair-memory-cmk16gx4m2a2133c13

 

[geofelt]

Four thoughts:
1. a 2 x 8gb kit will cost less and perform equally well as a 4 x 4gb kit.

2. As a gross metric, divide the speed by the cas number to get a figure of merit for ram.
Unfortunately, higher speed comes with higher cas numbers, negating much of the benefit of faster speed.
Actually, with a discrete graphics card, all ram performs about the same.

Here is one test of ram scaling on skylake.
http://www.silentpcreview.com/article1478-page1.html

3. If you want to oc your cpu, pick ram with standard 1.2v. Faster ram needs 1.35 and will consume some of the power overhead and limit your oc a bit. 2400 speed with a low cas number is good; do not anguish over the decision.

4. Fancy heat spreaders are mostly marketing. They are only of use if you are a competitive ram overclocker.
Moreover they will interfere with some air coolers.

 

[BadActor]

You can see in this video below that faster RAM does make a difference in some games. Some games it doesn't. The higher frequency usually gives higher bandwidth which may explain why it matters in some games and applications.

https://www.youtube.com/watch?v=mSU0UWFCa1Y

 

[Tradesman1]

Chris3488,

What CPU and mobo, that will determine what you can run. Regardless look to 2x8GB rather than 4x4GB as it's less stress on the MC (memory controller) and you want a nice balance of high freq and low CL. If say going a 6600K or 6700K, I'd look for something like the 3000/14 Ripjaws V or Trident Z, nice high freq and very tight CL

 

[iamacow]

Easiest way to determine speeds is to divided speed by CAS. Example 3200/15 =213. so something like 2400 with CAS 11 is 218 so the 2400 technically preforms better.

In games you will see 1-3fps difference from 2133 to 4133 ram. So really it is whatever is cheaper and has the amount of memory you want. The sweet spot if 3200 CAS 14 for money vs performance.

 

[rhysiam]

Chris3488,

What CPU and mobo, that will determine what you can run. Regardless look to 2x8GB rather than 4x4GB as it's less stress on the MC (memory controller) and you want a nice balance of high freq and low CL. If say going a 6600K or 6700K, I'd look for something like the 3000/14 Ripjaws V or Trident Z, nice high freq and very tight CL

The cheapest 3000/14 kit from a big-brand I can see on partpicker is $105 vs like $65 for a range of decent 2133/2400 14/15 kits.

This is described as a "gaming-only PC"... are you guys seriously suggesting this is a good use of a budget for a gaming rig? I'll defer to your knowledge here because you know much more about RAM than I do, but it seems to me for a gaming build there will almost always be better places to put that money than into fast RAM. If we're talking a no-compromise monster rig then sure, why not, but any other "normal" budget constrained rig making a case for faster RAM is pretty hard isn't it?

I looked at the youtube benchmarks linked above, but they run counter to the recommendations of sites like TH & Anandtech. Even if you take those benchmarks and decide 2666mhz is important, you can get a corsair kit like that for $75. I just don't see the value proposition for a $100+ kit in a gaming rig myself.

 

[Tradesman1]

Games today, more and more are using DRAM and utilizing better than in the past, Fallout 4 has shown gains of 10% + in FPS, it's also been seen in many games that faster DRAM raises minimum FPS and average FPS. The amount of DRAM also continues to rise, don't expect these trends to change. Part of my business is building rigs, higher end gaming and business systems, with Skylake (these days) 2800-3200 is the preferred pick for both gaming and business. Also DRAM prices are way down, about this time last year a 16GB set of 2400 DDR3 sold for about $160-200. I wrote an article this time last year on 32GB sets and those I teted ranged from about $325 on up. The Haswell prices were lower than Skylake, but serious gamers were paying much more than today for good DRAM (also note that was a year ago and 2400 was popular them

 

[BadActor]

Games today, more and more are using DRAM and utilizing better than in the past, Fallout 4 has shown gains of 10% + in FPS, it's also been seen in many games that faster DRAM raises minimum FPS and average FPS. The amount of DRAM also continues to rise, don't expect these trends to change. Part of my business is building rigs, higher end gaming and business systems, with Skylake (these days) 2800-3200 is the preferred pick for both gaming and business. Also DRAM prices are way down, about this time last year a 16GB set of 2400 DDR3 sold for about $160-200. I wrote an article this time last year on 32GB sets and those I teted ranged from about $325 on up. The Haswell prices were lower than Skylake, but serious gamers were paying much more than today for good DRAM (also note that was a year ago and 2400 was popular them

This follows the conclusion I have drawn regarding faster memory speeds. If your willing to spend 10 or 20 dollars extra on a graphics card that's clocked higher than a competitor and gives another 5 or 10 FPS, then spending a little more for RAM that does the same thing is worth it.