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GTX 260 power question.

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December 31, 2008 9:03:37 PM

I have a GTX 260 it says it needs minimum of 500W (36A on 12V rail). I have a Cooler Master Real Power Pro 850W that has 4x 12V at 18A and 2x 12V at 28A. The video card takes two 12V. So my question is is there enough amps to run the card fully? Does putting two 12V at 28A make the card's available power at 24V at 56A or is it still 12V at 28A?

Also what are the rails in the power supply?

Thanks,

Chris

More about : gtx 260 power question

a b U Graphics card
December 31, 2008 9:22:42 PM

mrwaffles said:
I have a GTX 260 it says it needs minimum of 500W (36A on 12V rail).

"It" doesn't need all that power, that's the recommendation for the "system" you wish to install it in.
a b U Graphics card
December 31, 2008 9:30:52 PM

DellUser1 is right. The 12 volt @36 amp is a minimum suggested power for, I think, the "average" or "typical" system - what ever that means.

A GTX260 by itself needs about 14 amps.
Related resources
January 1, 2009 6:11:14 AM

So with a system of Q6600 2.4ghz quad core, 4gigs of ram, one harddrive, one cd drive, and the GTX260 is the power supply good enough to run it all fully? Sorry, I don't know anything about power.
a b U Graphics card
January 1, 2009 12:46:28 PM

Your psu could probably run 3 of them without a problem.
January 1, 2009 4:21:14 PM

Alright. Thanks for all the help.

Chris
January 1, 2009 6:55:22 PM

What exactly is a rail? What's the difference when I hear people say a single powerful rail is better than numerous less powerful rails?
January 1, 2009 9:18:39 PM

That's all very interesting. Why then would the GTX manual state that it needs 36Amps on 12V rail? It seems in that article they just talk about 20Amps on 12V being completely satisfactory. I'm just confused as to why the requirements don't match up with the actual physical requirements. Like jsc was saying why would it suggest 36 amps if the GTX only really requires 14?
January 1, 2009 9:32:48 PM

Yeah well they state that it need 36amp recommended because they don't want customer get mad because they would say its recommended 20amp on 12v rail and they have 10 hard drive and 40 fans that just won't fit, i guess they don't take the risk. I think 14amp is pretty low, Even 20 amp is pretty much the limit. Depend what cpu, ram, hard drive, fans etc.. you running. Higher amp, watt is always better then limit.
a b U Graphics card
January 1, 2009 10:30:33 PM

mrwaffles said:
Why then would the GTX manual state that it needs 36Amps on 12V rail?

People tend to miss the fact that that is the "system" power recommendation, 14a for the card, maybe 4-8a depending on the cpu, another amp per hard drive and optical drive, a couple three for the mb, maybe 1 or 2a for fans and you don't want to be running the psu to the edge of it's capabilities so a bit of a buffer is figured in.
January 1, 2009 11:29:01 PM

I see. So I shouldn't expect my frame rate to increase any when I get a new PSU? Currently I'm running 30 at 5 on my enermax and the GTX 280 I use (the original poster Chris is a buddy and we're sharing accounts here) I wasn't really satisfied with my 30-45 FPS in Farcry 2 and Crysis (no matter what I set the visual settings too) and I was hoping that it was the Enermax limiting my frame rate, and not my 3.6Ghz Core2Duo E6600.
January 1, 2009 11:40:42 PM

What is your average fps if you do Farcry 2 benchmark tool: Run 1 ,ultra high ,1920x1200, no aa ?
a b U Graphics card
January 1, 2009 11:42:27 PM

mrwaffles said:
Currently I'm running 30 at 5 on my enermax and the GTX 280

You lost me with that, please explain more clearly.
January 2, 2009 4:37:04 AM

The enermax ratings say it does 30V at 5amps.
January 2, 2009 4:52:43 AM

I can't run 1920x1200 so I did 1280x960, everything very high.

* Total Frames: 2535, Total Time: 51.00s
* Average Framerate: 49.70
* Max. Framerate: 73.37 (Frame:392, 6.65s)
* Min. Framerate: 35.65 (Frame:1734, 34.58s)

That doesn't seem like the kind of preformance you would expect from a GTX 280.

My setup:

core2duo E6600 @ 3.6
Nvidia 680i Motherboard
Enermax 750 Watt PSU
GTX 280 with latest drivers
Vista 64 Service pack 1
4 Gigs G.Skill DDR2 1066 PC8400
January 2, 2009 5:20:40 AM

PSUs don't limit framerate, unless your card can't get enough power and is downclocking itself, but it'd be much harsher than what you're experiencing. And I've never seen a PSU that put out a 30 volt rail, are you sure it's not a 5 volt rail at 30 amps? That's pretty common.

Graphics cards run on 12 volts, so that's what's really important.
January 2, 2009 6:19:19 AM

I might have got it backwards and you're probably right. Is that frame rate normal? I'm running Crysis Warhead on the "Gamer" settings at 1280x960 w/ no AA at around 30-45 frames. Is that a normal rate for a GTX 280?
a b U Graphics card
January 2, 2009 6:34:17 AM

For a 280, that sounds a bit low; my GX2, which for Crysis is about the same as a 280, gets around 35-45 on highest settings (NO AA, 1650x1080). AA kills Crysis for any setup right now, and you shouldn't try it above 2x at most.
January 2, 2009 7:08:44 AM

So what exactly is killing my frames?
January 2, 2009 4:05:31 PM

I did the same benchmark on my GTX 260 Core 216. I got

# Average Framerate: 54,63
# Max. Framerate: 85,51
# Min. Framerate: 37,96

Just to compare at 1920x1200 at ultra high benchmark i got 46 fps average difference is not large. But first off, if you playing at 1280x960 you didn't took the good card sure it suppose to do better but if you want to do a real test do a 3d vantage mark or 3dmark 06 test. Also your psu is fine. I am running on a 520w psu with 54amp on 12v rail and im sure i could use a gtx280 without any problem. Try 3dmark 06 and come back us with the result.
January 9, 2009 12:12:51 AM

Hi guys sorry it took me awhile to get back to you, I've been busy. I just did a Vantage benchmark and this is my result:

13089 3DMarks

Is that good for this system:
core2duo E6600 @ 3.6
Nvidia 680i Motherboard
Enermax 750 Watt PSU
GTX 280 with latest drivers
Vista 64 Service pack 1
4 Gigs G.Skill DDR2 1066 PC8400

I just got a new PSU and if I get a chance I'll put my new one in tonight and re run the benchmark. This just doesn't seem to be running fast enough for a GTX 280. Something smells amiss.
a b U Graphics card
January 9, 2009 1:02:34 AM

srgess said:
I am running on a 520w psu with 54amp on 12v rail

That's impossible
54a X 12v = 648w
Check your psu label and see how many watts are available to the 12v rail/rails.
If it's a Corsair520, it's actually a single rail psu with a 40 amp output
January 9, 2009 2:41:27 AM

I just swapped out for a PC Power & Cooling silencer 750 Quad PSU. It has a single rail apparently. 3D Mark Vantage keeps crashing now so I'm trying to figure out what's wrong.
January 9, 2009 3:07:34 AM

So now everything keeps crashing when I try to run it. I used EVGA Precision to check GPU temperature (I haven't overclocked the GPU) and it hits about 77 degrees C when the games/3D Mark crash. How could a new PSU cause my GPU to over heat?
January 9, 2009 2:39:33 PM

Guys, on a very related suject:

Do you think that a Cooler Master UCP 900w is enough to run a pair of GTX 260 in SLI, on an overclocked Core i7?

This is the rail distribution for the UCP 900


I just ordered that PSU and recently found people voicing concerns about the anemic 12V rail.. :(  The GTX 260 especifications on the manufacturers sites indicate a minimun of 35A on the 12V rail, but some vendors say "combined 35A on the 12V rail", while others left out the "combined" part... your toughs would be much appreciated.
January 10, 2009 12:05:20 PM

OK, I´ve done more reading on the subject... so let me post my conclusions in case they are useful to somebody else:

1. Multiple 12v rails or single 12v rail? It doesn't really matter for the graphic card.. the card will simultaneously suck power from the motherboard, the 6 pin connection and the 8 pin connection (if the card is so equipped) as long as all those connections can supply clean 12 volt power. If the 12v is coming from a single rail or not is the same for the card (as long as it is clean power).

2. When the card manufacturer says "a minimum of 35 amp on the 12v rail", that figure is for all the combined 12v rails on the PSU, and is accounting for the ENTIRE system consumption, not just the card.

3a. The main difference between single and multiple rails PSUs is that on a single rail the entire 12v power is available for whoever need it without risk of overloading the rail.. the trade-off is that then the rail is subjected to wider electrical ripples and general power inconsistencies due to the varying demands of all your hardware adjusting to the system load.

3b. With a multiple rail configuration, (on most PSU) the 12v is still coming from the same single transformer, but is channeled and regulated in smaller groups, so if the load in one of those groups/rails change drastically, the other should remain unaffected. Here you get more consistent and isolated power while the trade-off is that now you have to decide what loads you put on each rail to prevent individual rails from overloading.

3c. On a multi-rail PSU, the amperage given for each rail is the maximum load you can put on each... but there is NO GUARANTEE that you can FULLY LOAD them all AT THE SAME TIME. Since on most PSU the 12v originally comes from the same place, the PSU might be dynamically allocating part of it's 12v to each rail.

An hypothetical example: The PSU has a 35amp transformer, yet it advertises 12v1=20amp, 12v2=20amp... so 20+20=35? Kinda if the rails really are 15amp each, with 5 extra amps that can be dynamically allocated to the rail that needs it the most. If you actually place 20amp on both rails at the same time the PSU will overload. Unfortunately the PSU makers don't market these little details, so your best shot at knowing the true history for your PSU is reading tons of reviews where they load the PSU to the max on all rails at the same time.

4. The Cooler Master UCP 900w is more than adequate to run a GTX 260... what did you/I expect from a top of the line PSU commanding such a high price :lol:  ?
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