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psu and gpu troubles

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  • GPUs
  • Power Supplies
  • Graphics Cards
  • Systems
Last response: in Systems
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January 8, 2014 10:31:28 AM

Hello, I'm new to the "industry"

I'm custom building for the first time.
(Desktop)

The graphics card I wish to run says it requires 750W psu
Does this mean it will pull 750w?

Silly question, maybe. But I have been recommended a 600w evga psu to run with my build and I was wondering if this was going to be possible.

I am new, please don't hesitate to give me a heads up on anything. I'd prefer to learn.

Thanks for your time

More about : psu gpu troubles

January 8, 2014 10:37:19 AM

The wattage on your power supply is the maximum amount of 'power' that it can put out. Your computer will only draw as much power as it needs and as a result, the power supply will only use as much power as is required to do that. Let's say you had a 400W load on your 750W power supply, it would only put out the 400W and therefore it would only use around 400W of power.

Think of it like this, you have enough power to run 7 light bulbs, but you only turn on 2 light bulbs. Therefore, you are only using 2 light bulbs worth of power even though you really could turn on 7 and be fine.
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January 8, 2014 10:46:12 AM

It's also important to understand that not all PSU's are the same. You can tell by the rating of the PSU and you'll typically see as gold, silver, platinum, etc...

Cheap PSU's will struggle to provide a "clean" amount of power, especially at their upper range. A high quality 500W PSU is better than a cheap 650W power supply on any day. I think a general rule of thumb is that if you want to cheap out on a PSU, to get a higher Watt rated one, that way you're less likely to run it at it's upper limit.

The other rating you might see (80) is the efficiency. PSU's tend to be less efficient when running at lower wattage - this is important because if you leave your PC on most of the time, it's going to be idling a lot and always drawing power on the lower end. Higher efficiency means you'll actually use less electricity, especially when your PC is not drawing a ton of power.
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January 8, 2014 11:08:07 AM

Okay, I understand.
I was recommended the 600w psu (evga 80+) and was told that it'd handle the gpu I wished to use
XFX AMD Radeon R9 290 4GB PCI-Express which states it needs 750w.. now if thats pulling 750w alone then surely I'm going to need something closer to 850w? Will the gpu be pulling 750w constantly?

Thanks

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January 8, 2014 11:18:08 AM

Good question - the rating required for a video card is a generic requirement and they "guess" as to what other components you'll be powering. The video card by no means will be drawing 750w alone - not even close by a long shot.

They assume that you'll have a CPU, a motherboard, a hard drive, a DVD ROM drive, they take the average of what it would take to power those things, then they add a "slop-factor" to it and say that the video card requires 750W. Most likely your whole PC will never draw more than 500W, even with everything running at max - but they don't know what else you're powering and most people aren't smart enough to know how much of a PSU to get. So they guess for you and tell you what kind of PSU you'll need by overshooting. If you're abnormal, and have like 12 hard drives, you might run into problems at 750W - or if you're running 2 or 3 video cards.

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January 8, 2014 11:29:16 AM

To answer your second question -

I found this review here on tomshardware for the 290x card:

http://www.tomshardware.com/reviews/radeon-r9-290x-hawa...

You'll see the card idles at 20 Watts, pulls closer to 180 when gaming and peaks at 225. So no, the card does not pull a constant amount of power.
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January 8, 2014 11:30:05 AM

Ah I see, so they're just covering their a**es basically.
That makes sense now because I was looking at my list of parts thinking "surely this shouldn't be pulling close to a kW" I could warm a small room with that running.
Thanks for the help mate.
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January 8, 2014 12:40:36 PM

I was looking into getting an 80+ bronze I believe. Now after reading that I'd much prefer a gold.
I'll have a search round and check out some benchmarks.

Which do you use and what kind of system is it used on?

Cheers
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January 8, 2014 1:04:49 PM

I bought a 1000W 80+ Bronze PSU for my system a few years ago. I was running an I7 2600K OC'd, 2 HDD's, 1 SSD, a DVD ROM, 8 GB RAM, and 2 GTX 470's in SLI and about 5 case fans. I might have been able to get away with 850W, but I wanted the room just in case I added something, plus the GTX 470 was a power hungry video card that would run at 95C on load!

I recently upgraded and am now running an I7 4930K OC'd, 2 HDD's, 2 SSD's, 32GB of RAM, a GTX 780, a GTX 470, a water cooler (H110), 6 case fans and I'm running it all on the same 1000W PSU. Even now, the 1000W is a bit overkill, especially since the GTX 780 doesn't use as much power as the GTX 470. I really don't want to have the GTX 470 in there, but I found out the hard way that if you have 2 monitors at different refresh rates, it won't work right with both running off of the same card (I have a gaming monitor at 144Hz, and another monitor at 60Hz).

If I had to buy one today for my current system, I would probably buy an 850W 80+ Gold. I could still go GTX 780 SLI if I wanted to with that and it should be adequate to power all of my stuff.

One thing to note is that there is an error in that article. The article says this: "An 80 PLUS certified 500W PSU will only deliver 80% of its rated output; in this case, 400W." This is wrong, an 80 PLUS certified 500W PSU will deilver 500W, but will use 600W from your home electricity.
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January 8, 2014 1:36:32 PM

Hmm, that's pretty interesting. I assumed the bronze would be poor in comparison to a gold but if you can run all of that comfortably on a 80+ bronze (850w) then I might not necessarily write off the idea completely.

I'm still learning as you can tell, hopping from idea to idea a lot at the moment.

Cheers dude
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January 8, 2014 2:09:14 PM

I'm glad you brought this up - I've actually learned a little bit more about 80+ Certified in the process of answering your question. What I didn't know was that 80+ Certified is only about efficiency. Efficiency is basically answering the question of how much power is wasted from your PSU. A 50% efficient 400W PSU means that it will actually USE 800W while delivering 400W to your computer. Wikipedia actually does a pretty good job of explaining it: http://en.wikipedia.org/wiki/80_Plus

I know for a fact that not all PSU's are able to deliver CONSTANT and CLEAN power at their maximum power rating. It's very similar to home theater amplifiers if you've ever looked into it. A cheap amp will say it's rated at 500W, but that's PEAK power. It might be able to hit 500W, but barely, or it sounds terrible and can't deliver 500W for very long. It's better to look at RMS, which is more about sustained power. A high quality amp from a reputable brand will will blow away cheap amps rated at twice the power. In the same way, a 750W Corsair is WAY better than a cheap 750W from a no-name.
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January 9, 2014 3:17:18 AM

Exactly, it was the same with car subs "back in the day" when you had the loud mouths with the cheap 1200W trying to knock your 500W amp that blew theirs out the water.

You paying for quality, it's just down to finding the balance between budget and performance.

There's no way I'd settle for a 50% psu.
I think bronze 80+ will do me fine. I'm not running a great deal compared to your hdd and ssd warehouse.

My main concern was down to running the gpu as I'm focusing on the video editing side of things.
Saying that.. I will probably have a couple of hdds by end of play.
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