C2D E6400, P45, HD3850 draw 77W idle, need less!

tuomaspt · Post by **tuomaspt** » Mon Jun 21, 2010 4:14 am

I have a system as described in the topic and at idle with a low power harddrive it draws 77W from the plug, which translates to about 62W power usage, because I am using PicoPSU 150W and a power brick with 80% efficiency.

Do you run a S775 system that draws substantially less power at idle? I can get to about 50W (~40W usage) power draw using a old PCI videocard, but I think that is still a bit high for CPU, motherboard and harddrive alone.

Would a newer S775 CPU get it substantially lower? According to some Intel specs an old E6400 draws 22W idle, while newer chips only do 6-8W.

ilovejedd · Post by **ilovejedd** » Mon Jun 21, 2010 7:09 am

Frankly, I think you'd be better off replacing the HD 3850 with the lower power one you already have. I'm getting 35W idle on my Celeron E3300 but that's with iGPU (GF9300) and 2.5" 5400RPM HDD. I think 40~60W is what you might expect using a traditional 3.5" HDD and dGPU. Unless, you're already planning on replacing the CPU to get better performance, I don't think you'll be able to recoup the CPU cost with the savings from electricity.

Klusu · Post by **Klusu** » Mon Jun 21, 2010 11:21 am

Your numbers are normal. A newer s775 CPU draws about half of what E6400 does. Your GPU is also 2 generations from current.

tuomaspt · Post by **tuomaspt** » Mon Jun 21, 2010 10:27 pm

Thanks for advices. I think I will wait calmly for a E7400-E7600 with Intel VT-x to come available used for a good price and then switch. It will save at least good amount of unnecessary heat in idle state, if not money.

Actually the GPU I am running is still very competitive for GFLOPs per Watts, at least according to the figures at Wikipedia's Comparison of AMD graphics processing units (can't link). It also sucks in less power at idle (13-14W) than any comparable HD 4xxx or HD 5xxx. Of course for gaming it is not that great, but I use it more as a simd calculation unit.

BillyBuerger · Post by **BillyBuerger** » Tue Jun 22, 2010 10:17 am

tuomaspt wrote:Actually the GPU I am running is still very competitive for GFLOPs per Watts, at least according to the figures at Wikipedia's Comparison of AMD graphics processing units (can't link). It also sucks in less power at idle (13-14W) than any comparable HD 4xxx or HD 5xxx. Of course for gaming it is not that great, but I use it more as a simd calculation unit.

Your own measurements show more than 13-14W idle. 77W (~60W) with the 3850 and 50W (~40W) with PCI means that it's using 27W (~20W) idle. And you can assume at least a couple watts for the PCI video as well which puts it more around 30W (~22W) idle. My own measurements with my Sapphire HD4670 Ultimate show it using about 16W AC (~12W). I also have a HD3650 here at work and it definitely runs warmer at idle than the 4670. I haven't done any power measurements on it though.

croddie · Post by **croddie** » Tue Jun 22, 2010 11:48 am

tuomaspt wrote:I have a system as described in the topic

Replace the whole system.

AuraAllan · Post by **AuraAllan** » Wed Jun 23, 2010 5:41 am

77W sounds like alot to me for a system like that.

I had this E4500, G33, HD3870, Samsung 3,5" that drew 67W idle.
My E4500 was undervolted but the HD3870 I used in that system used considerably more power then your HD3850.

Try undervolting your CPU and see if it helps a bit.

ilovejedd · Post by **ilovejedd** » Wed Jun 23, 2010 6:54 am

AuraAllan wrote:77W sounds like alot to me for a system like that.

I had this E4500, G33, HD3870, Samsung 3,5" that drew 67W idle.
My E4500 was undervolted but the HD3870 I used in that system used considerably more power then your HD3850.

Try undervolting your CPU and see if it helps a bit.

Sounds about right. Conroe uses more power than Allendale. I think it has more transistors and higher cache, too.

FÃ«anor · Post by **FÃ«anor** » Fri Jun 25, 2010 8:40 am

Based on some Googling (not 100% reliable) it sounds like the box of your HD 3850 recommends at least a 450W power supply.

If that is indeed the case a PicoPSU won't cut it.

tuomaspt · Post by **tuomaspt** » Fri Jun 25, 2010 11:27 am

BillyBuerger wrote:Your own measurements show more than 13-14W idle.

Yes, I was wondering about that. This thing seems to take more like 18-22W. Still, it is on a par with comparable current generation cards. Several sites have measured it at 13-14W, seems mine is worse.

FÃ«anor wrote:Based on some Googling (not 100% reliable) it sounds like the box of your HD 3850 recommends at least a 450W power supply.

The box itself says that. Of course, it won't need more than it really draws. A 150W PicoPSU can be enough for a card drawing at worst something like 70 watts if the rest of the system does not ever suck up anything close to 70 watts. As for reality, this system even boots up to OS with a 83W brick, but it is too close for comfort and won't survive load of GPU and CPU. Also the PicoPSU datasheet says it is only designed to operate at 65% of total output power unless the PSU is kept under 65 degrees Celcius. I wouldn't run a system taking much over 100W peak during typical usage with it, at least without a fan.

ntavlas · Post by **ntavlas** » Fri Jun 25, 2010 12:53 pm

Something that is often said is that you don`t want to replace components for the sake of power efficiency alone as producing those will take more energy than what will be saved during their lifetime.

Now if noise/cooling is an issue it`s a different story. You could also mitigate the above if you sell/give those components to someone who would otherwise buy a new computer.

It seems that your 3850 draws a bit more power than usual (30ish vs 20ish). The figures without the gpu look quite normal to me. You could try lowering the gpu clocks and voltages which could save you 10 watts in a best case scenario. Undervolting the cpu could save another 5 watts (again being optimistic) and maybe there are a few more to be saved by disabling unused components on your motherboard.

C2D E6400, P45, HD3850 draw 77W idle, need less!

C2D E6400, P45, HD3850 draw 77W idle, need less!

Re: C2D E6400, P45, HD3850 draw 77W idle, need less!