Need advice on RAM: low voltage? How many sticks to get?

[DaRuSsIaMaN]

First of all, I am running a 2500k (not overclocked--just got the k for the better iGPU since I won't use a discrete card). I want to get a new set of RAM, 8GB total.

I am concerned with performance AND power consumption. First, is it better to get 2x4gb or 4x2gb? I thought that having 4 sticks would allow faster operation for the same reason that SSDs are faster when they have access to more NAND chips. Is it true or false? Secondly, which setup gives lower power consumption, the 4 sticks of 2gb or 2x4gb sticks? Or no difference?

And what about low voltage RAM? The whole point of low voltage RAM is so it consumes less power right? Or does it also carry benefits when overclocking? How much of a difference will it make in power consumption?

Thanks!

[Arbutus]

For the best reliability now and for the many years you own this computer you should:

> only buy QVL memory
> never overclock
> never overvolt
> never undervolt
> always have some air flowing

Some people say Reliability is Job 1.

[DaRuSsIaMaN]

Thanks. Well, I'm neither going to overclock, nor undervolt. But, I still need to know:

1.) whether there is a difference in getting 2 modules of 4GB RAM vs. 4 modules of 2GB RAM.

2.) How much impact there is in getting low voltage RAM (which was made that way by the manufacturer, not undervolted by me) in reducing my PC's power consumption.

[SebRad]

Hi, I would say the energy useage and heat production of RAM can for practical purposes be ignored! I can't see it being more than 10w between any cases you can dream up. Most simple RAM works fine with no heatsink on it at all so really cannot be using much energy!

Intel s1155/s1156 and AMD are on "Dual Channel" ie two DIMMs is enough for max performance, infact four can be slower due increased loadings and may not be possible to clock so high, not that you plan to do that. s1366 can use "triple channel" RAM, need 3 or 6 DIMMs and usually have 6 slots on the motherboard.

I would get 2x4GB as this leave two slots free to upgrade down the road. The price premium for 2x4 or 4x2 is very small too. I would recommend getting 1.5v rated RAM in the speed you want (1600 is ample for stock i5-2500) from a big reputable brand, eg Kingston, Crucial, Corsair to name but a few.
Seb

[cmthomson]

In current PCs, 2x4GB is better than 4x2GB. (I'm going to ignore the high-end 3/6 slot or super-high-end Xeon systems here)

This is because the memory controller has two busses, and each buss can support one or two sticks. When you install 4 sticks, you reduce the electrical/timing margin of the system. This means either you can't clock as fast, or you increase the probability of errors, depending on how you clock/volt your system.

The other reason for choosing 2x4GB is that you can get DIMMs with tall heat sinks that won't bump into a tower CPU heat sink. These run cooler and typically at lower voltage (a double advantage). Install them in the slot pair farthest away from the CPU socket (this also has a small electrical advantage to do with signal integrity).

These days, memory power consumption is quite small; about the same as a hard disk (ie, less than 10W). But still, less power means less heat, which requires less air flow, which means a quieter and more reliable system.

I'd suggest a pair of 4GB 1.5v sticks with integrated heat sinks. If your budget allows, get sticks with lower CAS latency (probably about $30 more); this will improve folding or video encoding performance.

[MikeC]

Thanks. Well, I'm neither going to overclock, nor undervolt. But, I still need to know:

1.) whether there is a difference in getting 2 modules of 4GB RAM vs. 4 modules of 2GB RAM.

2.) How much impact there is in getting low voltage RAM (which was made that way by the manufacturer, not undervolted by me) in reducing my PC's power consumption.

Agree w/ both SebRad and cmthomson... and here's my 2 cents.

1) 2 sticks tend to play nicer w/ each other than 4. And it leaves 2 slots for future expansion.
2) No real impact in power but again, low voltage sticks have always been more "universal" for us in the lab -- they tend to work fine with any motherboard/cpu while higher voltage RAM is sometimes fussier about what hardware it will work with.

[DaRuSsIaMaN]

Great, thanks for the help, guys. 2x4GB sticks it is, then.

Btw, I actually found a review which specifically tests low voltage RAM and its impact on both power consumption and performance and provides some real numbers. It's by Tom's Hardware, and as usual, there are more charts than I want to see, but here is where the useful stuff is:
http://www.tomshardware.com/reviews/lovo-ddr3-power,2650-7.html
along with the next page, which sums up multi-threaded performance. The power consumption difference is marginal, between 1 to 4W depending on whether it's at idle or at load, but the surprising thing is that the low voltage RAM is actually slightly faster... Interesting! (Or at least, the same RAM is slightly faster at lower voltage. I'm not exactly sure on their testing methodology but I think they just increased the voltage on the same set of RAM to make the comparisons.)

[mkk]

Yeah the power consumption is a marginal effect. I'm however happy with my ADATA low voltage (1.35V) "gamer" RAM, 4x4GB DDR3 1600MHz memory. They weren't expensive, have a simple heatsink (which I value mostly for protection) and run cool. Can't hurt to have a little less stress on the RAM chips.

[DaRuSsIaMaN]

Oh, btw, would there be any issues running low voltage RAM on a H67 motherboard? I have the P8H67m-Evo. I dunno why I'm concerned but just want to be sure... I guess because I know people adjust voltages when OCing (I really don't know much about it), but the H67 can't do any OCing, so... ?

Also, does anyone know of any other kit that is 2x4GB, 1600, and 1.25V other than these gskill snipers:
http://www.newegg.com/Product/Product.aspx?Item=20-231-461&SortField=0&SummaryType=0&Pagesize=10&PurchaseMark=&SelectedRating=-1&VideoOnlyMark=False&VendorMark=&IsFeedbackTab=true&Page=2#scrollFullInfo

[Abula]

Also, does anyone know of any other kit that is 2x4GB, 1600, and 1.25V other than these gskill snipers:
http://www.newegg.com/Product/Product.aspx?Item=20-231-461&SortField=0&SummaryType=0&Pagesize=10&PurchaseMark=&SelectedRating=-1&VideoOnlyMark=False&VendorMark=&IsFeedbackTab=true&Page=2#scrollFullInfo

The only other 1.25V i seen are Kingston Lovo, i have one set on my MiniMi build, but they dont come in 8gb kits, but 4gb. On 1.35V you can also try G.SKILL ECO Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model F3-12800CL9D-4GBECO, but personally i think the Gskill snipper are good, i also have a set running on the MicroMi build, no issues at all.

Oh, btw, would there be any issues running low voltage RAM on a H67 motherboard? I have the P8H67m-Evo. I dunno why I'm concerned but just want to be sure... I guess because I know people adjust voltages when OCing (I really don't know much about it), but the H67 can't do any OCing, so... ?

Not all motherboards support sub 1.5V, most do, but even then, not all are compatible fully, check your Mobo manufacturer for details, usually asus has an approved memory list on their manuals.