Underclocking CPU and GPU

[MountainKing]

I bought my rig 3years ago (e6600)and had it running fine oced to 3ghz. Nowadays, I dont encode anymore or do CPU intensive tasks...I mostly download (24/7) and browse the internet...

I just underclocked my CPU to 1.2GHZ (200x6) and the vcore has been set to 1.0000.
Similarly, I underclocked my GPU 7600GT to its lowest clock speed and memory speed using rivatuner.

My question is, what are the benefits of using such a setup besides the system outputting less heat?

Do I REALLY save anything on my electricity bill? (I have a generic 450 watts PSU)

My understanding is that the PSU outputs the power at a constant output...So how do you save electricity when underclocking your components?

 

[Ben90]

You definately save a lot of power undervolting/clocking that much; now how much that relates to money savings may be trivial depending on how long u keep your computer running
watts * hours * Electricity_Price = Power_Bill

PSUs definitely do not suck juice out of the wall at a constant rate... They are however less efficient the further away from their optimal output is (normally around 75%)

 

[cusideabelincoln]

I wouldn't say a 75% load is the normal "optimal" effeciency for a power supply. It really does vary, and I'd say around 50% is the median of PSUs. Some will be more efficient at lighter loads, and some at higher loads; it differs greatly from what I've seen.

A PSU only outputs the power needed by the system. When underclocking your system needs less power, the power supply will supply less power, and less electricity is used from the wall outlet.

 

[yacoub]

You should check out SilentPCReview.com 's forums, there are like-minded folks there who could give you a better answer. Generally, as Ben90 noted, you want to run a PSU at or near its peak efficiency. So look at the PSU reviews at SPCR to see where the efficiency is best for a given model, and get one that accommodates your undervolting/underclocking setup so that you're truly making the most savings, if that's what is important to you.
Keep in mind, components also run cooler when they are undervolted/underclocked and not being used as much, so they give off less heat, which in turn means you can use less fans to keep the system cool or at least would be able to also undervolt them too (slows them down).

 

[Idontcare]

(Not much love for the AT forum community here I guess )

OP, both Ben90 and cusideabelincoln posts are spot on. Reducing the clockspeeds and/or voltages of power-consuming devices on the output side of your PSU will reduce the PSU's power-consumption at the wall (which is what you ultimately end up paying the electric company for).

You do not need to operate your PSU at its peak efficiency, the efficiency rating just tells you to not expect to see a 1:1 ratio of power-consumption reduction when it comes to reducing CPU or GPU power-consumption by 1W you may only see a 0.5-0.8W reduction at the wall because the PSU itself has variable (load dependent) efficiency.

That said, reducing power-consumption of your GPU/CPU will always result in some >0 power-consumption at the wall, it would just be a higher reduction if you happen to have a higher efficiency PSU at the load levels your rig is operating is all.

I doubt SilentPCReview forums are going to disagree with this information, but perchance they do then please update your thread here with your findings so we can all further educate ourselves on the subject.