Power requirements - Really???

stealthgeek

stealthgeek

stealthgeek

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Im starting to wonder if there is some sort of cartel involved in selling more and more powerful PSU's - allow me to explain:

Last week I tried overclocking my 6970 to see if I could get a few more FPS in BF3. I used the overclocking utility in both the ATI CCC and Afterburner, but I couldnt get ANY stable overclock - I could get into the game for maybe 30 seconds, but then Id get the driver lockup and recovery popup. I experimented with 100% fan and more power, but got the same results. Im pretty sure it wasnt temps, as with 100% fan the OC temp was actually cooler than my stock load temps! This made me wonder if my 620w PSU is struggling....

So, googled PSU calculator, input my details and it spat out Recommended PSU wattage should be about 650W.....interesting....

I started to browse OCUK for a replacement PSU, thinking this must be the cause, Ive had it for a few years so perhaps the capacitors just arent up to the job any more.... Had my eye on the Antec HCP 1200, as I thought this is the last PSU I want to buy, Id also like the future possibility of Crossfiring if I wanted to.

I hovered over the buy button, but then remembered - a guy at work has a power meter! Surely this will tell me if Im straining the PSU to its max?

I went home last night and plugged it in - was surprised at the kettle boiling took 2700 watts! But apparently, this is pretty standard - at least I knew the meter was working....

So I plugged it into my PC - about 150-180 watts booting up, which settled to something around 180. I fired up BF3 expecting to see 600 watts, or there abouts..... I didnt see the meter go above 300 watts, this was on Metro - so, I fired up a 64 player Caspian Border server, this would surely max out the PSU, right? Wrong - 330 watts AT MOST. Ive got a 2nd monitor so was able to see both my CPU and GPU at near 100% utilization - surely if there was a non-benchmark, real-world test to see how much power my PC is drawing, this is it, right?

This is totally baffling me, I cant explain why my power usage is so low compared to the recommended PSU wattage for my setup - surely something is wrong somewhere? I did wonder if perhaps some power settings in my BIOS myabe limiting the power draw, perhaps some 'green' features? If that were the case, why would I be seeing around 30-50FPS on Caspian and 70-90FPS on Ultra on other maps?

Totally baffled with this one...:confused:
 
I think a lot of people really dont know that a PC doesnt use up a lot of juice. Massive PSU's are a waste of money.
 
Power meter's show the power draw at the wall which is what the psu draws from the mains to supply the required wattage. Your actual pc will be pulling even less from the psu so you have plenty of headroom yet. Even my rig only pulls 400w at the wall and even then only by using Furmark and Linx both at the same time. Normal gaming use is anywhere between 230w and 340w depending on the game.

Unless your psu is developing a fault is would say your problem lies elsewhere.
 
stealthgeek said:
Im starting to wonder if there is some sort of cartel involved in selling more and more powerful PSU's - allow me to explain:

Last week I tried overclocking my 6970 to see if I could get a few more FPS in BF3. I used the overclocking utility in both the ATI CCC and Afterburner, but I couldnt get ANY stable overclock - I could get into the game for maybe 30 seconds, but then Id get the driver lockup and recovery popup. I experimented with 100% fan and more power, but got the same results. Im pretty sure it wasnt temps, as with 100% fan the OC temp was actually cooler than my stock load temps! This made me wonder if my 620w PSU is struggling....

So, googled PSU calculator, input my details and it spat out Recommended PSU wattage should be about 650W.....interesting....

I started to browse OCUK for a replacement PSU, thinking this must be the cause, Ive had it for a few years so perhaps the capacitors just arent up to the job any more.... Had my eye on the Antec HCP 1200, as I thought this is the last PSU I want to buy, Id also like the future possibility of Crossfiring if I wanted to.

I hovered over the buy button, but then remembered - a guy at work has a power meter! Surely this will tell me if Im straining the PSU to its max?

I went home last night and plugged it in - was surprised at the kettle boiling took 2700 watts! But apparently, this is pretty standard - at least I knew the meter was working....

So I plugged it into my PC - about 150-180 watts booting up, which settled to something around 180. I fired up BF3 expecting to see 600 watts, or there abouts..... I didnt see the meter go above 300 watts, this was on Metro - so, I fired up a 64 player Caspian Border server, this would surely max out the PSU, right? Wrong - 330 watts AT MOST. Ive got a 2nd monitor so was able to see both my CPU and GPU at near 100% utilization - surely if there was a non-benchmark, real-world test to see how much power my PC is drawing, this is it, right?

This is totally baffling me, I cant explain why my power usage is so low compared to the recommended PSU wattage for my setup - surely something is wrong somewhere? I did wonder if perhaps some power settings in my BIOS myabe limiting the power draw, perhaps some 'green' features? If that were the case, why would I be seeing around 30-50FPS on Caspian and 70-90FPS on Ultra on other maps?

Totally baffled with this one...:confused:
Click to expand...

I am averaging 400W and peaking at 450W on BF3 with 6950 crossfire, and that's at the plug (with a Gold PSU).

PSUs work best around 50-75% load, being away from the maximum PSU load means it runs cooler, with less fan and less stress, meaning longer life. A good PSU can run at full load quite hapilly, at least for a good while.

If you run Furmark / MSI Combustion, you will stress out the VRMs and increase the power usage over what a typical game requires.

With your setup, I'd pick up a Antec 550W or some such, it will be perfectly adequate.

Unless you run extreme setups, you don't need a big PSU, but keep in mind headroom for overclocking as well (between 50-100W extra required).

So yes and no, PSU requirements are often over-specced, and you can get away with lower rated PSUs, as long as they are any good. Also, some PSUs are designed to take SLI / crossfire (4 pin connectors), while others aren't and although it is possible to run these with dual GPUs, it's not always recommended (power distribution may be a problem).

In the end, do you want to trust your PSU to handle your rig, or potentially fail?
 
650W is what i'd recommend for two 6950s, not one 6970. these PSU calculators are completely pants. i;ve been recommended 750W for two 480s in SLI (when it needs more like 850W) and ive also been recommended silly high amounts for other builds

if you want a PSU for crossfire 6970s then i think the 700W lepa gold rated one is what id go for (if its powerul enough, i'm only about 90% sure that it is)
 
Its rated at about 80% efficient, so will be passing on about 240watts to the components. Ive checked a Bit-tech review for the 6970 and they had around 300 watts draw from the socket on an i7 setup, so perhaps this is correct!

Just confused as to why there is a push to 800+watt PSU's when a 400W will do for most systems, even high end systems. Granted, theres more breathing room if you decide to add more HD's, go Crossfire/SLI or get a water-cooling setup, but these are niche setups, surely?
 
stealthgeek said:
Just confused as to why there is a push to 800+watt PSU's when a 400W will do for most systems, even high end systems. Granted, theres more breathing room if you decide to add more HD's, go Crossfire/SLI or get a water-cooling setup, but these are niche setups, surely?
Click to expand...

My recommended specs.

550W for single GPU (bar 480 / 580).
650W for any single GPU.
650W for crossfire 6950 / 560ti and below.
750W for SLI 570 / 6970 and below.
850W for SLI 580.

These would be comfortable, but as I say you can get away with a lower tier PSU, although I don't like to recommend PSUs without a lot of headroom and inadequate connectors, to allow for longer life and potential overclocking. I'm not considering Crapola PSUs, that can't put the wattage on the 12V rail in a hot box.
 
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I usually estimate

1GPU 450-550w
2 GPU 600-750w
3 GPU 800-1000w

Total system usage at 80+ with a decent headroom.

EDIT/ SNAP
 
What psu calculator did you use? I would be interested to see what this one recommends for your system.

http://extreme.outervision.com/psucalculatorlite.jsp

I think there is some over estimation going on. One good reason from companies like nvidia and ATI is that there are a lot of cheap PSUs sold and whereas a good 450 maybe enough a cheap 450 may blow up. Hence they are likely to recommend a higher wattage.

Another disadvantage of too big a psu is that, as has been said, they are most efficient in the middle of their range but this means that at low utilisation they are inefficient. If most of your use is general browsing and your pc spends a lot of time idling then if you have too powerful a psu it is going to be running inefficiently.
 
stealthgeek said:
This is totally baffling me, I cant explain why my power usage is so low compared to the recommended PSU wattage for my setup - surely something is wrong somewhere? I did wonder if perhaps some power settings in my BIOS myabe limiting the power draw, perhaps some 'green' features? If that were the case, why would I be seeing around 30-50FPS on Caspian and 70-90FPS on Ultra on other maps?

Totally baffled with this one...:confused:
Click to expand...

It's always been like that, most setups use nowhere near the amount of power the PSU can output. If everyone got a power meter to see their usage they'd probably buy proper PSU's for their needs. There's nothing wrong with your PC.

Just get a good quality reviewed PSU with a wattage to suit your needs. Like it's been said PSU's run most efficient at 50% ish load so factor that in too, although nowadays the good PSU's are so efficient the difference in efficiency between the lower load and 50% is quite small. So only over a long period of use will that inefficiency start to cost you. ie 86% efficient at 25% load and 90% at 50% load.
 
My current spec doesn't go above 360 W from the wall with the 2600k at stock runing the CPU at 100 % load with Furmark maxing out the card. (on my old 600 W (432 W +12 V) PSU)

I shall see what is uses with the OCed 2600K at some point.

My PSU purchase was with the next 7 years in mind as I probably will get crossfire/SLI at some point. :) £20 per year seems a fair cost for a PSU.
I know I can pretty much run any 2 card setup with it.

Plus on idle it's runs as a silent no fan PSU.
 
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