QX6700 Wattage under load

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JethroXP

[H]ard|Gawd
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I thought this might be of interest to a few people. I recently purchased a Kill-a-watt meter, it's a device that allows you to measure the wattage consumption of any electrical device.

Using it to monitor my new QX6700 system (spec in sig) this is what I found:

Idle: 200 watts
1 core under load: 250 watts
2 cores under load: 280 watts
3 cores under load: 295 watts
4 cores under load: 310 watts
4 cores + 8800GTX loaded: 390 watts

I applied load by running instances of SP2004 on each core, and 3DMark06 to load the video card. Given that the QX6700 has TDP of 130 watts, it would seem that when idling it's probably consuming roughly 20 watts. Putting all four cores under load adds 110 watts. Loading the 8800GTX adds another 80 watts. Overall I was pleasently surprised to see that under max load I was only drawing 390 watts. I purchased a 750watt PS under the assumtion that full load would be 490 watts (roughly 65% utilization). This means I've got even more headroom than I was planning on. I suppose this goes to show that those new 800watt and 1000watt Power Supplies that are coming out really are overkill.
 
I would be careful about saying whats overkill when it comes to PSUs without knowing someones full system, I don't think you can say these sorts of things aren't necessary, All depends on what you are running, I was seeing near 600w load with 2x 7800GTX512s, X2 @ 2.75Ghz, 2Gb, Xfi and Physx plus a few drives etc. changing to 7900Gtos dropped that by 40w per card, if I popped 2 8800GTx in it would stand to reason I would need more power as 8800s draw more than the 7800GTX512 so I'd be up in the 6-700w area and R600s well from reports :eek: , this is measured with a similar device to you on an 85% efficient PSU, having underspecced a PSU in the past ran the original system on an OCZ 520w SLI PSU which died due to overloading (incidently this wasn't an efficient PSU and pulled near 900w from the wall socket compared to the 600 with the FSP700W)

doesn't hurt to have too much especially if its doesn't cost you that much more over a slightly lesser spec PSU, you don't know what you might run on it in the future.
 
You are not really running a loaded system there,... just a good proc and a video card.
 
Ockie said:
You are not really running a loaded system there,... just a good proc and a video card.
Click to expand...

Exactly what I was thinking. For me you can go ahead and add 3 DVD burner drives and 4 HDD's. Then put most of those devices to work and tell me how much your load is.
 
HDs use about 20w.

His system uses 2 HD's... So add an extra 50w or so to his topend score to get what yours would be.

And I agree, 800w PSU should be the highest on the market.
 
I suppose I should qualify my statement about overkill by adding "...for most people". Obviously some of you guys live for overkill and will stuff 10 HDDs and 5 DVD burners into a case just to see if it will melt ;)

My point was that for the average person, even an enthusiast, an 800 Watt or more Power Supply is just wasted capacity right now. There are obvious benefits from having that sort of head room, but even if I were to have two 8800 GTXs in SLI, I'd probably be barely hitting 500 Watts under full load, or about 66% utilization of my 750 Watt PS.
 
er, hang on, you are measuring the AC watts going into the power supply and assuming its 100% effecient. Your numbers are still good but only as percentages of increased load as you add more load.

hmm, so hard to describe. for 100W AC in you are not getting 100W DC out. There is at least a 20% loss in the power conversion inside the supply. So you have even more headroom than you thought because the wattage of the power supply is rated in actual DC output wattage. Dont see any sense in worrying about what rails use how much of whatever voltage. Still very interesting info on how loading a quad core affects a power supply.

I believe I have this correct but of course welcome additional insight or corrections.

Oh and I am with you to the max on the over hyped power supply wattage "arms race" the machine in my sig uses a 420W so-so quality supply and runs like a champ. for how long might be up for debate !!!
 
Good point, 390 Watts in does not equal 390 watts out. According to the manufacturer, my power supply is "...up to 85% efficient" and at the load I'm putting on it, I'm right at that maximum efficiency curve. So the 390 Watts in is more like 330 Watts consumed by the system. Makes the point even stronger that 1000W (and I just saw a 1200W) power supplies are just wasted on the average user, even the average [H] user.
 
Fully OC'd, a QX6700 with 8800GTX SLI and watercooling for the CPU (Coolit) my power meter was 820 Watts. Just to compare.
 
JethroXP said:
Good point, 390 Watts in does not equal 390 watts out. According to the manufacturer, my power supply is "...up to 85% efficient" and at the load I'm putting on it, I'm right at that maximum efficiency curve. So the 390 Watts in is more like 330 Watts consumed by the system. Makes the point even stronger that 1000W (and I just saw a 1200W) power supplies are just wasted on the average user, even the average [H] user.
Click to expand...

You are correct... they are wasted on the average user, those 1000w psu's are used and needed by oc'ers though. On air or water cooling you probably don't need one, but what happens if you start seriously oc'ing? With DI or LN2 you are going to be dumping a lot more vcore into that cpu ;) So I agree that the average [H] user doesn't need a 1kw psu, but some people do :) Saying they shouldn't be made is ridiculous.
 
boshuter said:
You are correct... they are wasted on the average user, those 1000w psu's are used and needed by oc'ers though. On air or water cooling you probably don't need one, but what happens if you start seriously oc'ing? With DI or LN2 you are going to be dumping a lot more vcore into that cpu ;) So I agree that the average [H] user doesn't need a 1kw psu, but some people do :) Saying they shouldn't be made is ridiculous.
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I don't think anyone in this thread has said they shouldn't be made. Just saying that they are likely wasted on the majority of people who buy them, thinking that just because they are building an OC'ed SLI rig that they will need a 1000W PS. Clearly it's possible these days to build a machine that requires one of these, but based on my observations I believe there are very few machines (built with currently available components) that will need one.

I'm not trying to bash 1000W Power Supplies. Just offering up my own obersavation so that someone who is considering building a similar system won't feel the need to spend the extra money on power supply that will be mostly under utilized.
 
Yes, others have done testing with a QX6700 + 8800GTX + a nice system and have shown it cosumes less than 400W.

Then adding another 8800GTX for SLI is still under 500W. (example here)

Then again they haven't run them long term (ie: 2-3 years) to verify if the PSU will actually hold up under that type of use.

Quality goes a long way. Nvidia, AMD, or Intel have always set their PSU requirements based on the worst case.
IE: a MAXED out case (lots of harddrives, DVD's, etc) AND a cheap quality PSU.
So if they say you need a 500W PSU, they're taking in to account that you might have a fully loaded system & bought the cheapest 500W PSU around. But technically you could get buy with a 400W quality brand PSU.
 
Don't go by the Inq article. I think they simply peaked out their PSU so there was no more wattage to measure.

Also, when sizing a PSU, make sure you are in the 70% load max range. Most PSu's get very ineffective after that load and simply produce heat and become less efficient.

My system draws 820 watts at the wall during benchmarks which is, assuming 85% efficiency, about 690 watts or so which is right on the money for a 1KW PSU.
 
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