I have a quick couple of questions, I am looking to build a new rig hopefully in the next month or two. I currently have a phenom II but the thing sucks so much power out of the wall that I am looking to sell it, and go to either a sandy bridge 2500k or a amd bulldozer depending on when they come out and how the performance and power usage stacks up etc. Anyway on the sandy bridges, I know this is a very power efficient design power gating etc, but why is it that they clock down to only 1600mhz on idle? I know most of the amd systems go to 800 by default and with k10stat I can even get 400mhz. It just seems like a waste when most web surfing, and low quality vid streaming could be done at lower speeds.

Also, for a 2500k sandy bridge system, running say one 7200 rpm drive, and a ssd, and using the onboard graphics, what is the least psu or best choice for saving power? I am guessing something like a seasonic s12 380, or antec earthwatts 380 would be a good choice? I am guessing the seasonic would be the better supply? I have a neo eco antec 620 supply currently which has worked well without any problems but I am thinking it would be better to let it go with the amd system...

If what you say is true, then that must be because power consumption at 1600Mhz is low enough (about 3W for a dual-core).


pico or equivalent

well I assume 1600 is the idle mhz just from reading tons and tons of posts on various messageboards. It seems to be what everyone refers to as idle speed. I think it's great if it only used 3 watts at 1600 but heck it could be 1 or 1.5 haha.

I have read of people using picos but I do not want to go that route, I do at least want a self contained standard type psu
I should have clarified that, but still I guess if people are running them with only 150 watts that answered my question

According to CPU-z its either 1.6 idle or max turbo speed at any type of load - leading me to believe its inaccurate. But if I look at Intel Extreme Tuning it shows a wider range of idle freq of 1.6-2.4 and load also varies a bit.
Either way what matters for power consumption isn't the core freq, but more the core voltage that is typically under 1V at idle (depending on motherboard)

I'd go for Seasonic Gold X400 FL. It is very efficient. If not the gold get a 300W 80+. A pico could be a good idea, unless you are planning a video card in the future.

It is actually quite hard to get efficiency figures on ATX power supplies for the current standard idle operating points. I've just set up a i5-2400 on a H61M/U3S3 mobo, with WD green 2TB, and an Antec SU-380 power supply (in NSK-3400). It draws 37W on idle from the wall. The test review here only goes down to 58W input power, by which point the efficiency was severely dropping off. So extrapolating test figures, I'd get around 17W lost in the PSU, and 20W drawn by the system. The X-400 is definitely better though, and based on the review here, I'd be drawing around 30W from the wall if using it.

But given the much lower idle power draw these days, it'd be good to start seeing power supply specs published down to around 20w output.

The X400's efficiency at low loads is predictably bad.
There's only one conventional PSU I've seen measurements of which is efficient for your purpose and that's the Kingwin Platinum. Expensive but not (much) more than some overpriced PSUs which are recommended here. At least this one delivers something unique.

The X-400 efficiency at sandy bridge loads, while not great, still seems better than most. But as you say, the Kingwin is a step better again.

thanks for the help! I would like to stick with the standard psu form factor, I am not planning currently to run a seperate graphic card but I admit the option to do so would be nice, so I don't really want to go with a pico. This kingwin supply only goes down as small as a 550 watt but it is still more efficient than even a 380 or 400 watt supply even at such a low power draw? I wonder why they will not make a 300 or 350 or so watt supply that is platinum level? It seems this would be more needed. I mean does someone running a 850 or 1000 watt supply really care how efficient it is? I'm betting they don't...

I know at this point alot is speculation but has anyone heard how the 4 core amd bulldozer will be on power consumption compared to the sandy bridge systems?

Out of curiosity - what is your goal in moving to a more power efficient system? To save money? Upgrade to a more powerful processor? Have a little fun building a new system? Or all of the above?

If it is with the goal of saving money, you might want to crunch some numbers first to see if your plan makes sense. I'm also running a Phenom II (x3 710) - with the complete system pulling about 65 watts from the wall. When I read the reviews for the new i3-2100, I thought it looked like a great solution to replace my CPU/Motherboard with something more power efficient.

Here's the thing though - at 65 watts, and about $0.12 per KWh, it would only cost me about $70 a year to run this machine 24 hours a day. And I don't even run it 24 hours a day - it is sleeping half the time - so it's more like $35 a year in electricity costs.

Meanwhile, to buy a new i3-2100 and H61 motherboard is going to cost at least $140 (current price at Microcenter). I would also need to upgrade to DDR3 memory (currently using DDR2) for about $60.

So assuming that my i3-2100 system draws half as much power (say, 30 watts), I'm looking at saving about $20 a year in electricity costs with the i3 over the Phenom II (assuming it sleeps half the day, or $40 a year if I were to run the system 24/7). At that rate, it would take 10 years to make up the price difference, by which point I will have long since upgraded to something else. And it would take considerably longer to make up the cost on the i5-2500k system you are looking at.

From what I've seen, it just isn't economical to throw out (how much do you think you can sell yours for?) a working CPU with something that draws less power in the hopes of saving money. Of course, with the i5-2500K you will also be getting a pretty big performance boost, so that might be a better reason to look into upgrading. But I personally haven't run into any situations yet with my Phenom II where I thought, "Damn, I need a faster CPU".

So that brings me to the last reason possible reason for upgrading to Sandy Bridge: boredom. One of these days I'll probably be bored one weekend and find myself driving down to Microcenter in search of a new weekend project. And if that's where you're coming from, I totally feel your pain.

You are right there is zero reason for me to upgrade. I have never had my system bog down on me. Pretty much any quad core nowdays up near 4 ghz is a beast, and even though I multitask and do some photoshop and encoding etc not many people including myself have a usage profile that is even going to make the thing breath hard. I love to build systems, and if I could line up a buyer I'd build a new one every month or two just to be doing it. I have a good friend that buys most of my systems as I build new ones, and what I end up doing is hooking him up and giving him a good deal, and then adding a couple hundred to what I get from him and building a new system. I just built this one after christmas, but even as soon as I had it built there were things I wish I'd done differently. First off, I wish the thing was quieter, I really would like my next system to be very quiet, I'm sure total passive cooling probably isn't a option but I am going to put alot of thought into the heatsink and cpu fan part of it for sure. My system sits on my desk right beside my ear and I have gotten used to using netbooks and laptops more in the last few years. The other thing is, this last system I built has a radeon 6850 in it...so under heavy gaming or running prime95 etc it can pull up towards 400 watts out of the wall according to my kill-a-watt. I think it idles at around 150...I ended up deciding that I really don't have to have such a powerful video card because I am using a older 4:3 monitor with lower resolution than some are running nowdays, and I also sometimes end up playing games that aren't brand new and require alot of muscle anyhow. I like the idea of sandy bridge and the upcoming amd bulldozer having built in graphics that are enough to get the job done, but save tons of power and less noise etc. In my mind though the whole sandy bridge thing wasn't very viable until these new z68 boards came out. I also ended up going with a samsung f3 spindle drive instead of a ssd, but now since I had built it, the 3rd gen ssds are out I'd like to use that on my next one. I wish I had a microcenter reasonably close to me but then again I would probably stay broke Anyway I appreciate everyone's suggestions and help, I guess my goal is to build a fairly powerful desktop that will game some, and will turbo up to at least 4ghz if needed without using so much electricity. Right now I find myself not even using my desktop much because I certainly don't want to leave it running all day. It would be nice to have something that could idle at a low power state and not heat up the room 20 degrees haha.