GPU on 300W psu

[Toad772]

Looking to figure out if my pc can run an HD 6770
My hardware consist of:
1 500gb hdd
1 ODD
E8600 cpu
300w psu(came in dell pc don't know the brand, but from what I have read it is better than most other 300w psu)
HD 4650

According to this http://techgage.com/reviews/sapphire/hd_6770_1gb/power.png the max it reaches is 280 watts under a stress test and that is with a much bigger cpu and way more ram.

So what do you think?

 

[Rob Williams]

The way I see it, in our testbed which featured a much larger CPU (150W vs. 65W), and one that featured much more RAM and even a discrete audio card, we topped out at 280W using a stress-testing tool that pushes the CPU and GPU to the limits. I am not sure if PSU rails will have to be accounted for here, but given our top load with that same GPU, I'd say you'd have no problems at all.

I am not the most fluent in power, however.

 

[Tharic-Nar]

I'd say it would be unwise, mainly for the reason that the Dell PSU will be rated as 300 Watts PEAK, not sustained, so it's more than likely ~250 Watts sustained, possibly less. Then there is the question of power over the 12v rail, power conversion efficiency, etc, etc. Supposedly, the 6770 consumes about twice the amount of power the 4650 does.

I'd personally feel more comfortable around the 450-500 Watt mark, then at least you have spare capacity which lowers the strain on the PSU, extend life etc, plus further room for expansion, such as more hard drives or even being used in a new system.

 

[Toad772]

I'd say it would be unwise, mainly for the reason that the Dell PSU will be rated as 300 Watts PEAK, not sustained, so it's more than likely ~250 Watts sustained, possibly less. Then there is the question of power over the 12v rail, power conversion efficiency, etc, etc. Supposedly, the 6770 consumes about twice the amount of power the 4650 does.

I'd personally feel more comfortable around the 450-500 Watt mark, then at least you have spare capacity which lowers the strain on the PSU, extend life etc, plus further room for expansion, such as more hard drives or even being used in a new system.

That test rig peaked at 280 with a CPU that uses 90 more watts than mine and that is also when it is pushed, I would be running at 1400x900 so I would not be pushing it nearly as hard.

 

[RainMotorsports]

Definitly wouldnt risk it on the stock POS. If it was a reputable 350 Watt I would say go for it. I blew the big bucks on the Seasonic X750 thinking I might end up with Dual 580's or something. Single 570 overclocked and an i5-2500K at 4.5Ghz I barely push 350 watts at the wall full tilt folding. CPU only the machine doesnt break 190 at the wall if i remember correctly and once you factor in efficiencies what the output/draw is on the DC side which is what the PSU is rated for, output is actually less.

The other issue is not just the total wattage. Lets say it will output 300 watts combined all rails continuously. Issue is that rating accounts for the 5v and 3.3v rails. The machine isnt that old but still uses a cheapo power supply. I would be concerned with the rating on the 12v rail and being what it is you can't trust the documentation at all. As its been said with these cheapos the continuous ratings are often missing or hidden by the peak figures.

As Tharic suggest a nice 450 watt PSU should last you even provide some expansion room. You can obviously do your setup on a bit less but not off the stock PSU. If your going to buy mind as well middle it and get something from a reputable company with a little more power than you need for a price you can afford.

Then again you can try what I did with my 486 back in the day, when the hard drive speeds start fluctuating, you know you reached your limit.... serious....sad but serious. I am lucky that machine survived its days in my care.

 

[Tharic-Nar]

That test rig peaked at 280 with a CPU that uses 90 more watts than mine and that is also when it is pushed, I would be running at 1400x900 so I would not be pushing it nearly as hard.

The thing is, you'll be playing it at 1440x900 now... what about later? What about new games that stress the system? You could very well use a 6770 in the current system, it may even work fine, but long-term stability would be in question; I'd rather not risk overloading the PSU, blowing it and causing a surge into the motherboard and frying it - yes, that really does happen.

The other thing as well is that the bench system uses an 80%+ efficient PSU, a lot of the unbranded's are 60-70%. Then as Rain makes note of as well, the labeling on the PSU itself is often misleading or the numbers are nonsense because there is no context. Is it 300 Watts peak? Is that 300 Watts at the socket or in the system? Does it state the Amps on the 12v rail?

Personally, I'd just rather not risk it. Most of us who have built systems or provide any kind of tech support to friends and family have had to deal with the consequences of a PSU gone bad.

Rule 1 for ANY system; don't skimp on the PSU, it'll bite you in the ass.

 

[Brett Thomas]

I'm gonna side with Tharic and Rain on this one, but I'm gonna go for a different reason:

The sustainable power draw on a PSU is actually not your biggest factor here. Though that matters (to prevent your system from shutting down) if you go over your actual capable production, you need to remember that not all VOLTAGE is created equal, either. In this case, screw wattage totals...

When you bring a PSU closer and closer to its max, more heat is generated. That heat does all sorts of things, but one of the biggest things to note is when a cheapo PSU gets really warm, its voltages tend to be less stable than at other times. That means 12V rails won't just only carry X amps of power through them, they may be carrying it at 12.5V, 11.5V, etc.

This particular variability is the most dangerous part of a cheap PSU and it's often overlooked. Drop voltage too much, the card doesn't function right. Increase voltage too much, the chips can fry. Your system is designed to have a steady march of REGULATED power. You break the regulator, you break the system - with potentially disastrous consequences.

Though I'm not a fan of spending money for nothing and I am in full agreement with both you and Rob that it will quite likely be able to produce the AMOUNT of power you need, I think you should strongly consider whether it will produce the QUALITY of power you need and act accordingly. As Jamie said - don't skimp on the PSU, it'll bite you in the ass.

Personally, I'd spend the extra $70-100 and buy something reputable (I'd vote around the 400W range just so you don't need to do it again, and I'm a fan of Corsair and Seasonic) that you can trust. The PSU is probably THE most under-respected part in your system, and it really, really shouldn't be.

 

[DarkStarr]

Just grab a nice little PSU, Corsair has the builder series 430w for ~$30 if you look around.

Personally I stick to Antec or Corsair, (hear that XFX is good too however) and there's a few others that I would go for but they are more of high end PSUs.

 

[Toad772]

So the corsair CX 430 V2 would be a good option?

http://www.newegg.ca/Product/Product.aspx?Item=N82E16817139026

 

[Brett Thomas]

Yep yep!

 

[Rob Williams]

Good choice Toad, and with the HD 6770, you are going to be kicking some serious ass. To call it a major upgrade from an HD 4650 would be an understatement.