Graphis card and power requirement

[mara-]

Hello everybody,

I'm buying new graphic card. I decided for GTX 460. But, I have one doubt concerning to power requirements. I have CoolerMaster Real Power M520 which has 520W. Rest of my components are in my signature. Now, I think this PSU should be enough when we look at wattage especially since this is 80+ efficiency PSU and since recommended PSU is 450W. My concern is 12V rail. If I figured this correctly from Cooler Master page I have 3x12V rail and each is capable of 19A. For this 3 rails there is 408W. So this does not make sense. If we divide 408W/12V=34A. So, these 3x12v rails can't give together 3x19A. But, my main question is will I be able to run this graphic card on this PSU. I read somewhere that it needs 24A. This card requires 2 x PCI-E 6 Pins connectors, so will that in combination give it enough power? Thanks in advance for any info.

Cheers

[Zenskas]

You should be fine

The PC in your sig is far from power hungry, and your PSU has two 6 pin connections plus enough amps on the 12V line to run it no probs.

The GTX 460 is way overestimating it's own power usage. There is no way it will pull 100% of the power the dual 6 pins plus the PCI-e slot itself is capable of providing. Decent upgrade too, I'm saving for a GTX 460 right now, but want to go Core i5 760 first

[mara-]

OK, thanks. I wold also like Core i5, but that's bigger investment for me now. It would require me to change motherboard and to get DDR3 RAM memory plus Core i5. Well, that's almost whole computer. I'm planing to do this, but it needs a lot saving. BTW, I'm getting GTX 640 768MB version. I would like to get 1GB version, but it's not available where I live.

Cheers

[Zenskas]

No worries, yeah the 768MB version is insane value!

Not as fast as a 1GB etc but about $50 cheaper over here. A 460 768mb costs about $10 less than a standard 260 did just before it was discontinued in Aus.

Win-win

[mara-]

I just asked if I could order 1GB version and it's is 50€ more, to much for me. And from what I could see in benchmarks, there is no big performance difference between two. Only at some huge resolutions there is some difference, like 5-6 frames, but nothing special for me. Thanks again.

Cheers

Edited August 13, 2010 by mara-

[CoffeeFiend]

I have 3x12V rail and each is capable of 19A. For this 3 rails there is 408W. So this does not make sense. If we divide 408W/12V=34A. So, these 3x12v rails can't give together 3x19A

It does make sense. 408W is the combined power, and that's 34A indeed. That's how much you can use in total, adding up usage on all 3 rails. You also can't exceed 19A on any single rail (that's a limitation protecting against melting wires and such)

especially since this is 80+ efficiency PSU

This makes absolutely no difference as to how much power it can deliver to your various computer parts -- that's 520W max. It just guarantees that it has a decent efficiency which translates into savings on your power bill.

[mara-]

OK, thanks for explanation. BTW, on their page 520W is continuous and max is 600W.

Cheers

[CoffeeFiend]

OK, thanks for explanation. BTW, on their page 520W is continuous and max is 600W.

That's creative wording by sales folks.

Max continuous = 520W

Max peak (for a short time i.e. until the overtemp protection kicks in) = 600W

You wouldn't really want to use over 520W for any amount of time. Not that running your PSU at 100% of its capacity is a good idea either.

That's very much like companies who sell audio amplifiers. We've all seen those before -- claims of 300W per channel, on a 8 channel amplifier, which you'd think would mean being able to deliver 2400W RMS total continuously to your speakers if that were true. But ~100% of the time (save for pro gear) that's creative math by sales people. It comes down to how much power a single channel could use (at the detriment of others), while using pretty much all the stored power inside all of the capacitors inside of the unit in a single microsecond (peak power) or something ridiculous like that. You just look at the power draw from the mains in the specs, and it says like 800W perhaps. Typical efficiency on those (push-pull setups) is 70%, so that could only deliver ~560W in total, across all channels, or 70W RMS/channel continuously (unless it somehow creates power out of thin air, by violating the very laws of physics). I've also seen a lot of computer speakers that claimed over 100W of power, while being fed by a 5W power brick...

Sales people always get creative like that to make their products look good -- often much better than they really are... especially when it comes to PSUs. That isn't a bad unit you have, but a lot of generic power supplies way, WAY over-state their real capacity. This is why you see cheapo 650W units dying at 184W load When it comes to power supplies, quality REALLY matters.

[mara-]

Yeah, I sort of knew that. I had that cheap supply that just died. And then I decided to buy a quality unit. This unit wasn't cheap at all for me, but I didn't know about the 12V rail thing. If I knew, I would need to add just some small extra money to get even better unit, but that's the past now. The price of my unit is the same as the year ago, so I could probably sell it for decent price (4 years warranty left) and get a new one, but while this one can satisfy the power needs I'll use it. Thanks for the info you provided.

Cheers

[Octopuss]

Just because a manufacturer says you need 600W or somethin PSU it doesn't necessarily make it so. This whole marketing bul***** about PSUs is dumb as brick. Very roughly said, unless you run VGA cards in SLI and have dozen of other devices, you don't need anything over 500 at all.

I have C2D CPU, 4GB RAM, two hard disk, extra network and soundcard, Radeon 5850, and even the 425W PSU I have is huge overkill.