Memory confusion: please help!

[alexo]

So I'm putting together a system from parts (Asus P8Z77-V, i3770K) and go over to http://ca.pcpartpicker.com/parts/memory to pick me a nice 2x4MB kit.

Apparently, for about the same price (in CAD) I can get:

DDR3-1600 CAS 7 (1.5v)
* http://www.gskill.com/en/product/f3-12800cl7d-8gbxm

DDR3-1866 CAS 9 (1.5v)
* http://www.gskill.com/en/product/f3-14900cl9d-8gbxl
* http://www.gskill.com/en/product/f3-14900cl9d-8gbsr
* http://www.crucial.com/usa/en/blt2kit4g3d1869dt1tx0

DDR3-2133 CAS 11 (1.5v)
* http://www.corsair.com/en/vengeancer-8gb-dual-channel-ddr3-memory-kit-cmz8gx3m2a2133c11b

DDR3-2133 CAS 11 (1.5~1.6v)
* http://www.gskill.com/en/product/f3-17000cl11d-8gbxl

DDR3-2400 CAS 10 (1.65v)
* http://www.gskill.com/en/product/f3-2400c10d-8gtx

DDR3-2400 CAS 11 (1.65v)
* http://www.gskill.com/en/product/f3-2400c11d-8gxm
* http://www.kingston.com/datasheets/KHX24C11T3K2_8X.pdf

Not to mention countless others for up to $10 more...

Ouch, my head a splode!

Can you please help with the choice?
Thanks!

 

[EarthDog]

I'd grab the 1866, any, amd call it day. Ram is ram is ram for most. Unless you are benchmarking, there is no need.for more than 1866.

 

[Shell]

If you're lazy like me just pick ram based on speed divided by CAS, so 1600/7 or 2400/10, and I'm guessing the former is a hell of a lot cheaper.

 

[wingman99]

+1 DDR3 1866 is all you need.

 

[EarthDog]

If you're lazy like me just pick ram based on speed divided by CAS, so 1600/7 or 2400/10, and I'm guessing the former is a hell of a lot cheaper.

 

[Shell]

CPU performance depends on latency more than raw bandwidth, it's doing a lot of random RWs, not pre-arranged sequential chunks like GPU.

http://en.wikipedia.org/wiki/CAS_latency#Memory_timing_examples

 

[EarthDog]

Right.. aware that...

So, the OP listed his uses of the machine?? What is if its a gaming machine?

I guess what it boils down to is that this is the first time, across nearly half dozen forums and 10 years, I have heard of that method (dividing speed by latency to choose ram). I mean it makes sense to get the lowest CAS for a given speed you can find of course, but, this method... seems... I don't know weird.

 

[Shell]

Gaming CPU wise is a weird one, it's mostly database-style, physics, entities, so lots of seeking around a lot of memory, on the other hand you often want to throw up something large to the GPU which is more a bandwidth concern, or perform big matrix operations, it's really mixed.

Multi-GPU uses a lot more memory bandwidth because you have to push assets to two or more GPU memory banks, that affects minimum frame-rates mostly.

In games you'll be dealing with MAT4(64 Bytes, 512-bit) and VEC4(16Bytes, 128-Bit) a lot, note the wiki article says words, the word size in x86 is 64-bits, and single channel RAM is 64-bits.

So to get a good idea of RAM's general performance... 2-word typically since you're be randomly reading vectors a lot.