How much power does PC memory use?

[cooper]

Okay, so it's once again time to think about putting together a new system, and since the energy bill is starting to hurt I thought it might be smart to go with low power use this time around. For most parts of the system it's pretty easy to work out how much power they use, but a notable exception here are the memory modules.

Voltage is being reported in the marketing material for pretty much all memory modules, but I can't find anything about the amount of ampere and/or watt they need. I read that DDR2 needs to dissipate 4.4Watt of power, but that was given as a ballpark figure and actual use can be very different. DDR3 was reported on that same page to require 30% less due to its lower operating voltage (1.5 vs 1.8) and other advances.

I've recently come across an announcement that G.Skill will soon bring to market so-called 'ECO' memory modules that draw only 1.35 volts. The question on my mind is if the reduction in power use is sufficient to warrant possibly pricier memory. It'll be somewhat slower than top of the line of course, but 7-8-7-24-2N should do just fine for me.

Thoughts?

[VaKo]

Honestly I think memory will be the least of your concerns when it comes to power usage.

[cooper]

True, but I'm wondering if the energy savings sufficiently warrants paying a higher price for the dimms assuming always-on operation and a 5-year lifespan.

If it's 1 watt less it's 11 euro's cheaper to run in electricity alone, and another source of heat less to worry about.

Assuming memory is on the 12A line, 0.15V less means 20 euro saved over its expected lifespan at current energy prices. Multiply by the number of dimms installed...

That, and I'd really like to know just how many amps memory operates on, not in the least because I can't seem to find an answer to that question dispite excessive googling.

I realise that bigger gains can be had by going with a decent video card or economic processor, but since I'm already trying to go low-usage, why not incorporate the memory with this aswell?

[Sparda]

Using an SSD instead of a normal hard disk for the operating system would be a good start. Then only using regular hard disks for every thing else and configuring them to spin down while not used. Then also using a motherboard and CPU that dynamical scale the processor clock speed based on usage. At this point it becomes very micro management, if you unplug the power and hard disk LED you save another couple watts.

[cooper]

Sure, it's micro management. But I get to pick right now. It may be minimal, but there's a "better" one. I'd like to pick that one and that means needing to know how many amps flow through the DIMM.

I've already managed to get my Mini-ITX based media player down to 20W under full load by simply combining it with a PicoPSU, a slow-ass flash disk (just for the OS. The movies are on the network) with an IDE interface on it and a generic stick of DDR(2? I forget) RAM. Getting that 2 watts down means 10% off. Not much in the grand scheme of things, but if you're going to spend the money anyways, why not...?

[moonlit]

Holy crap, it's Cooper!

I mean... yeah, personally I wouldn't worry too much about the RAM, but if I did then I'd probably buy performance RAM and underclock and undervolt it. If it's reasonably power efficient running at full tilt then you'd probably expect it to consume even less when it's not being stressed. If my theory is broken, do feel free to correct me, but it seems logical to me.