GPU Power Requirements

Kind of hard to give a simple yes or no answer to the question " Which one is it ? ".
Video card manufacturers power reccomendations are for the entire system, never the card alone and it's not required that it be thru a single 12v rail.

Please Pardon my mis-wording! But you got my point didn't you. (Not an insult, just frustrated that half the posts on forums have more to do with bashing people for their inability to use written English to explain their woes, than answering some poor dumb newbie's question that all the uber computer geeks or just plain a-holes think should be common knowledge to anyone who owns or uses a computer.)

So, here comes the hard part for me. Why should I believe your answer. This may be common knowledge to you, but apparently somewhere there is an argument against you. otherwise I would not be asking this question to begin with.

BTW, Thank you very much for answering my question so quickly and I mean absolutely no harm by my rant above.

Yep, I got your point.
Not insulted, nor was I trying to insult you.
There's absolutely no reason for you to believe me, let's see if I can get some back up and maybe you'll believe it when more people explain it.

The answer is ""24amp requirement is for entire system""

P=VI
=12*24=288 watts
And thats pretty high for a card...
So The rating is for entire system...

You need a PSU having 24A on 12V rail.

BTW What GPU are you using/Consider to buy?

No worries friend!

While I have not actually looked at the box for the card I want(its on newegg.com), I would think that it would be wise for them to state that these requirements are for the whole system and represent the suggested minimum for optimal performance. Of course, it probably comes down to money as all things do. If uneducated people see a requirement and decide to purchase a new PSU, then business is good right?

Well, Asuming you are correct. Would this PSU provide enough power to this GPU for Optimal Performance???

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...


Thank you again for your help.

So let me understand your post. At first it seamed to be contradicting itself, then I took a different look at it.

If the rail = all 4 connectors combined then a 4x12v/18A PSU should be more than sufficient correct?

If the rail = each 12v/18A connector then I would be underpowering the GPU by 6A, as no one rail could output more than 18A, Correct?

There's a single 12v source in most psu's *, split into multiple outputs, each limited by an Over Current Protection circuit.

An example of a true dual rail psu would be the Corsair HX1000 that has two 12v source's in the casing.

You're back to thinking that the card needs 24 amps, it doesn't.
Just an example; 8800 GTS 512 has a 24 amp psu reccomendation the consumption of the card is around 9 amps.

So in conclusion, my 630w 12v/18A PSU will run up to 18Amps to the GPU if it ever asks for that much. And if it ever did ask for more, it would just run a bit hotter but still no more that 18A, Correct?

Sounds like you have solved this puzzle for me. Thank you to all who contributed.

If your 630w can only deliver 18amps on the 12v rail, then that is the maximum power it can deliver to the entire system (216w) that draws power from the 12v rail. That's just about everything except the motherboard, memory, add-in sound card into the PCI slot and a few more.

Good quality PSUs can sustain 100% power and peak very, very, very brief above the rate 100% with no issues. However, the longer a PSU works near 100% the shorter the life span.

Cheap and average will likely overload and in the best possible situation it will shut down the PC. Worse would be the PSU gets fried. That worst possible situation is the PSU gets fried and it also fries some of your components or the entire PC.

A quick PSU calculator on Newegg.com suggests that I will need 386W. Would this be for the 12v rail or for my entire PC?

http://educations.newegg.com/tool/psucalc/index.html


My current PSU:

Brand RAIDMAX
Model RX-630A
Series VOLCANO
Spec
Type ATX12V V2.2/ EPS12V
Maximum Power 630W
Fans 2 x 80mm Blue Glowing LED Fan
Main Connector 20+4Pin
+12V Rails 2
PCI-Express Connector 2 x 6-Pin
SLI Ready
CrossFire Ready
Modular Yes
Efficiency Up to 80%
Over Voltage Protection Yes
Overload Protection Yes
Input Voltage 115/ 230 V
Input Frequency Range 50/60 Hz
Input Current 10A @ 115V, 5A @ 230V
Output +3.3V@30A, +5V@45A, +12V1@18A, +12V2@16A, -12V@1.0A, +5VSB@2.5A
Approvals CB, IEC, TUV, UL, CSA
Dimensions 6.5" x 3.5" x 6"



Just noticing that it has two 12v rails, would this make a difference. In theory I could have the GPU on one rail and the rest of the PC components on the other, right?

David - The answer to your original question is the current (amps) on the 12 volt rail(s) is for most, but not all, of the pc system. Here's why:

Modern PSUs have at least five separate voltage rails, sometimes more. Each rail is like an independent power source monitoring and adjusting the voltage on its outputs.

The most important rail is the 12 volt rail. It provides the most wattage, usually accounting for 75% or more of the power output of the PSU. It's used by everything, from the CPU which has a dedicated 12 volt connection on the motherboard to video cards which also have dedicated 12 volt connections, case fans, pumps, hard drives, optical drives, and a few other components. Other rails of varying output power other components like the motherboard chipset, RAM, USB, and the PCI-e bus.

I just happen to have the XFX Radeon HD 4770 video card installed in my personal pc. I wanted to find out how well the fan shroud exhausted hot air out the rear panel. It was introduced earlier this year as a excellent mid-level, general purpose video card that is energy efficient. It consumes very little power. It just happened that two 4770's operating in Crossfire mode actually produced good performance results during gaming. Technical reviews confirmed the card's energy efficiency. During a Furmark stability test which produces a heck of a lot more stress than any gaming session ever could, the card itself used a maximum of 85 watts. At 85 watts the current (amps) is very very low.

I took a look at the Raidmax Volcano. It can power a system with a 4770 video card. However, I would question the quality of the unit. Raidmax is not known for high quality power supplies. It lists a combined total of 34 amps on the 12 volt rail(s). A high quality 600 to 650 watt power supply typically has at least 50 amps on the 12 volt rails.

Corsair, PC Power & Cooling, and Seasonic are some of the brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Lately we've been seeing a few other brands offering some high quality units.

Thanks for the info, I am only in the market for a new video card at the moment though. I am sure when I have more money to throw around I will get a second 4770 and upgrade the PSU at that time. Til then I will continue to use the Raidmax Vocano 630W PSU. It has run just fine in my rig for the last 3-4 years.