Power supply and video cards

drthrd

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I want a better video card. I have picked out 2 cards. One requires a 300 watt PSU and the other requires a 400 watt PSU. I have a 430 watt PSU. If you already have a 400 watt PSU can you just stick in a video card that requires a 400 watt PSU or do you need to figure out your total wattage?
 

hang-the-9

Titan
Moderator
You don't need more power for either one. Get the 4650, it's a much better card. Although it looks like you are looking at AGP cards, which means the rest of your system may not be able to keep up with it.

Do you have a 3gig + CPU and at least 2 gig of RAM? If not, get the other one. Or neither and save a few hundred for a new system. The AGP video cards will not be movable to a new system, so they are wasted money if you have plans for a new PC within a year or so.
 

drthrd

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I have a old comp. I am not wanting to spend a lot of money on this old thing. My monitor went out and I got a a monitor that does 1080p and wanted a video card that could do 1080p. My current video card is a GeForce MX 4000.

I was posting to get some idea how to know how to pick a video card based on power supplies. If you already have the required PSU for a video card can you just get the video card or do you have account for the video card plus the rest of your system? If you have a good PSU that is. What is considered a good PSU? Multiply the outputs by their amperage and add them them up and if they add up to what the PSU then its good?
 

hang-the-9

Titan
Moderator
The recommended power supply is for the whole system, not just the video card. That is always higher than what is really needed. Either of the cards will run at 1080p, but the 4650 will be able to run games at that res pretty well. Of-course the rest of the system probably won't be able to, but that's another thing.
 

drthrd

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I meant the recommended power supply for the video card. The recommended PSU for the 4350 is 300 watts. Why do they recommend a 300 watt PSU? The video card is not going to use the whole 300 watts. If you already have a 300 watt PSU can you use the 4350 or do you need to upgrade your PSU?
 

hang-the-9

Titan
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They recommend 300 watts because the system power plus the extra power the card uses will add up to around that for an average system. You need a power supply to comfortably supply enough power to run the card and whatever else is in the system. If you have 20 hard-drives and an over-clocked Pentium D with 6 case fans, you may need more than the 300 watter even for a low end video card.

And when the manufacturer puts down the requirement they leave about 20% or maybe even 30% breathing room to rule out a cheap power supply crashing the system if someone buys it based on their recommendation. When they say 300 watts, if you have a good 260 watt power supply, it will run that card.

There is no power supply requirement for the video card on it's own, you may see a max power draw off the card though and some voltage requirements for the connections.
 

drthrd

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Ok I see now. They use average systems. So if you are not maxing out your PSU with lots of hard drives, case fans, burners etc.. and have a decent amount of watts left over then it is safe to stick in the video card. What is considered a good PSU? Multiply the outputs by their amperage and add them them up and if they add up to what the PSU then its good? Can you give a example of a bad PSU not equaling what it says it will do. Like a 400 watt PSU not really providing 400 watts. And a good PSU providing all or more wattage than it says.
 

hang-the-9

Titan
Moderator
No PSU will give you more than the rating, but they would give you closer to it than a cheap one. Some brands are better than others, you'd have to read reviews to compare models. http://www.tomshardware.com/reviews/Components,1/Power-Supplies,6/

It really depends on how they rate the power, some will do it in a freezing cold room with voodoo spells and get the rating once, and stick it on the box. Others will do a load test on a normal temp room and average out many tests.
 

One that can put 90% or more of it's wattage on the 12v rail, since that's where most of the computers power is drawn from.

You did that in your first post.

8 or 9 year old design with a 13 amp 12v rail, from a company that is known mostly for producing fireworks, that doesn't even qualify as a mediocre 200 watt psu.

Fireworks
http://www.youtube.com/watch?v=LTVEtr14FEA

 

drthrd

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Why is it only a mediocre 200 watt? Are you multiplying 12V x 13 amps?
 

hang-the-9

Titan
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He means it's a cheap one that won't supply it's rated power. It should run those cards fine though, at least the lower end one. Neither one needs an external power supply, it will get it's power through the AGP slot.
 

iam2thecrowe

Glorious
Moderator
basically with PSU's most of the time you get what you pay for. Radimax and any brand in that price range is always going to be poor. Unfortunately there is no law or anything stating how these components should be rated so all manufacturers rate them differently. If you build your own PC's you really need to put some research into power supplies. here is a good start
http://www.hardwaresecrets.com/article/Coolmax-CUL-750B-750-W-Power-Supply-Review/977/10
http://www.hardwaresecrets.com/article/410
 

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