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What if my GPU exceeds a 25 W power limit of PCI-E x16?

Last response: in Graphics & Displays
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January 6, 2013 7:09:55 PM

Hello Community. Well, I've got an HP Proliant Microserver N40L which I currently use as an HTPC and I use it for occasional gaming, too. About a year ago I put into it a Sapphire Radeon HD 6450 GDDR5 (clocks: 625/800 MHz). Although I am able to run older games (like TES IV: Oblivion) with decent details and framerates, now I would like to overclock my GPU and get the most out of my hardware. AMD's Overdrive allowed me to raise the clocks to only 725/900 MHz, but I managed to get using MSI Afterburner up to 750/950 MHz stable (no artifacts at all, the temps are acceptable). OCing this card is definitely worth it to me, because the FPS boost in games like Skyrim is good (from 34 to 39 FPS on the same scene, Ultra High details, 720p).

However, I am unsure of pushing it further because of the 25 W power limit of my PCI-E 2.1 x16 low profile slot. This card is sold with clocks 625/800 MHz (like mine) up to 750/900 MHz (according to AMD's website) and it's maximum TDP is 27 W. Do you think I would be fine if I push it to say 800/1000 MHz? I am even able to raise it's voltage, so the stability of the GPU shouldn't be a problem. The question is whether the mobo and the PSU will be able to handle the extra load or not. The PSU is weak (only 150 W), but my whole PC consumes only 70 W with the card at stock speeds under max load (Furmark). I appreciate any suggestions/help :)  .
a b U Graphics card
January 6, 2013 8:19:03 PM

Try it, let us know if it works. There are some nice small power supplies on newegg...

PCI Express Graphics 1.0 (PEG) cards may increase power (from slot) to 75 W after configuration (3.3 V/3 A + 12 V/5.5 A).[9] Optional connectors add 75 W (6-pin) or 150 W (8-pin) power for up to 300 W total.
a b U Graphics card
January 6, 2013 8:29:34 PM

By doing so all you will end up with is an unstable oc and crashes during gameplay since you will have an under powered gpu.
remember it is your mainboard providing power to your gpu so it might cause instability to the whole system itself.

do it at your risk.
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January 7, 2013 12:47:39 PM

Thanks for your replies. What do you think is the worst thing that can happen if it draws say 32 W under full load? Would it burn (damage the mobo or any other component) or just crash the system / cause some kind of instability? Because I would like to try it, but I am not sure about possible damage that may be caused to the system.
a b U Graphics card
January 7, 2013 12:54:51 PM

Shouldn't cause damage but no guarantees. If it doesn't work you might not boot or have stability problems if you do boot. If so, just remove it and you should be OK. Then look for a better power supply.....
January 7, 2013 3:00:10 PM

Thanks for the reply. Meanwhile I've done quite a lot of reserach about my card and found out that I may not be hitting the 25 W power limit even at 800/1000 MHz, because the TDP of 27 W applies for AMD's reference card running at 750/900 MHz and 1.15 V and my card runs originally only at 625/800 MHz and 1.0 V. As I have read, the actual voltage affects the power consumption quite a lot and since my card runs only at 1.0 V, the power consumtion should be lower than 27 W even if I overclock as long as I don't increase the voltage. Well... Let the testing begin :) .
January 7, 2013 6:37:31 PM

OK, I've played with it for quite a long time and found out that I can set the clocks up to 790/950 MHz stable. I pushed it even more to 815/1000 MHz, but a voltage increase by 0.02 V was necessary to get it working stable.

However, now under full load at 815/1000 MHz it makes not very loud but undoubtedly noticeable noise, something between clicking and electrical buzzing... I can't say for sure whether it comes from the GPU or from the PSU itself, but I suppose it is a bad idea to continuously use it with these settings, right?
a b U Graphics card
January 7, 2013 7:42:02 PM

this is a sign of the gpu over heating...the gpu fan runs as high as possible to keep the temps under control.
do keep an eye on the gpu temps always and all the time.
please beware not to fry your mainboard or any other components on it in the process of overclocking it too high.
good luck
a b U Graphics card
January 7, 2013 8:16:49 PM

Way-cool! Those little servers can do pretty good. HP always did make good server hardware.
January 8, 2013 5:09:40 PM

siddharthmukul007 said:
this is a sign of the gpu over heating...the gpu fan runs as high as possible to keep the temps under control.
do keep an eye on the gpu temps always and all the time.
please beware not to fry your mainboard or any other components on it in the process of overclocking it too high.
good luck

Well, I set the fan speed manually (fixed to 70%) and it makes that weird noise only under heavy load (>80%)... And the temps aren't very high, the maximum was about 74C. So I guess the problem is either an under-powered GPU or I need to increase the voltage a bit more ;)  even though this way I would increase the power consumption by another ~ 3-5 watts.

zdbc13 said:
Way-cool! Those little servers can do pretty good. HP always did make good server hardware.

Yeah, this little server looks well-built and reliable so far, so I hope it can handle a bit more load than it was made for :)  .
!