So admittedly i'm pretty uninformed on system RAM.
The item I've always prioritized has been the amount of RAM (in GB). I've understood 32GB to be better than 16GB. And I get why you would want to have 2x8GB sticks as opposed to 4x4GB sticks But what about if you have equivalent size ram but other factors are different?
For example, what should be prioritized for the following components/specs of RAM?
Timing
Cas Latency
Voltage
Speed
For example, How much improvement does moving from 2400 to 2666 or 2800 speed matter? Does the benefit scale linearly as you increase?
Is lower better on for Cas Latency, Voltage and Speed?
What is worth paying a little more for?
How do all of these things factor together so someone can pick the best ram for their system?
Obviously the usage matters, so I would say this question is tailored around DDR4 RAM for gaming purposes primarily. Thanks for any help.
(gross simplification here)
Speed = MHz/MT/s = higher is better.
Latency numbers (including CAS and primary timings): smaller number = less cycles needed = faster.
At the same speed, lower latency numbers = faster latency.
At the same latency number, higher speed = faster everything.
So long as voltage isn't well off the norm for a given type of speed and latency (standard DDR4 is 1.2V, performance kits 1.35V or so)
Speed, then CAS Latency, then the rest of the primary timings, that's my preferred order. Remember that latencies and timings are based off absolute clock cycles - don't be alarmed if the CL number seems to stay constant, or become bigger as you move up speeds. An easy way to get the actual latency (without actually getting the exact cycle time, not needed for comparative purposes) is to do this math:
(1 / Speed) * CL
Probably will yield relevant numbers, at least ones relevant enough to make comparisons. There's a more "real" way to get the exact cycle time needed...
I think as long as you get out of the bottom-rung parts of the memory (minimum DDR3-1866 CL9 or DDR4-2400 CL15 (perhaps higher for DDR4, definitely true for DDR3 for Haswell and Kaveri non-IGP) you shouldn't get bottlenecked by memory.
Seeing as these days, the premium for a DDR4-3000 CL15 kit isn't much more than a 2133 or 2400 kit, why not go straight for the 3000 kit? Just remember that you'll need a Z170 motherboard to make full use of it if you're on a Skylake CPU. (The same deal applies for DDR3 and Z97/Haswell.) Do ask if you need the rest of the Z170 feature set, too, before you buy OC RAM.
Very fast RAM is situational. You may or may not benefit, but usually high-end computational stuff and minimum frame times in CPU-intense games should be helped.
