4870 PSU question

[ThreatDown]

Ok, so I have a 550 Watt rosewill RP-550 PSU. It has 2 18a 12v rails. I have just gotten a 4870 and it works fine but I am a little concerned about the power supply. I know rosewill isn't the best but I just want to make sure my psu isn't going to be strained too hard and die on me or something.

My system is this:
95 watt AMD phenom II quad core 2.6 ghz
4 gb ram (1.9 volt)
3 WD SATA hard drives
Creative audigy 4
512 mb 4870 (stock clocks)
LG dvd burner

I am considering getting a new one but I don't have much money in my account to buy it online, I have 100 dollars in cash but the only store near me is staples and all they have is a 140 dollar 750 watt corsair thats too expensive.

 

[jimishtar]

550 should be ok, but a good brand, like corsair for example. try 2 find a quality 550-600 W psu. the rosewill should work fine.

 

[outlw6669]

Rosewill PSU's are JUNK!
I would highly recommend switching it before it catastrophically fails.

Look into a quality Corsair, PCP&C, Seasonic or Antec Earthwatts 500w+ PSU.
If you plan on adding a second 4870 in CrossFire later, get a 600w+ PSU from the above manufacturers.

Instead of shopping at a local big box store (almost always a rip off), check on Newegg.
They have an excellent selection, great customer service and very competitive pricing.
A quick glance located This Seasonic 500w for $67 which should work great for you.

 

[gkay09]

If you are not Overclocking your CPU or the graphics card, then that PSU can handle your config...

And you wont require that 750W PSU at all...Go for it only if you want to add one more HD 4870...Actually even the 650TX can handle 2 cards in crossfire...

Even an OCZ 500W Modextreme is more than suffice for your config...
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341016

Other options...
SeaSonic SS-500ET 500W
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151069

OCZ ModXStream Pro OCZ600MXSP 600W
http://www.newegg.com/Product/Product.aspx?Item=N82E16817341017

SeaSonic S12 Energy Plus SS-550HT 550W
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151027

 

[Onus]

That Rosewill is an old, inefficient design, but it isn't a Chokemax; I believe it may be similar to one that passed testing at jonnyguru.com. I can't imagine anyone buying one today, but if it is what you have, you should be ok with it.

 

[Guest]

The psu is ok mate, dont stress it by overclocking and it should keep pumping away untill you can afford a better psu, 600w good brand will do for you in the future but I went for 750w corsair for future cpu/gpu upgrades

 

[ThreatDown]

Well I just remembered a whole ago I replaced my dads busted dell psu with an corsair VX450. It technically has lower specs but since its a much better brand and has a single rail you guys think it would run my system better? I could easily swap them, my dads system doesnt require much power.

 

[ThreatDown]

Wow I think that 550 watt rosewill actually was bottlenecking my 4870, I had some nasty stuttering in crysis warhead. Popped in the VX450, smooth as butter!

I also did some math, the rosewill says it outputs 420 watt on the 12 v rails. Take that and 72% efficiency = 302 watts.

The corsair has a single 33a rail that does 396 watts. Take that and 80% efficiency = 316

So the 450 watt actually has a bit more headroom on the rails due to the better efficiency. Am I correct?

 

[jsc]

No. The efficiency is the ratio (output dc power)/(input ac power). At an output of 400 watts, the Rosewill will draw 555 watts from the wall. At the same power output, the Corsair will draw 500 watts from the wall.

 

[ubernoobie]

the higher amperage on a rail just makes it more stable for the graphics card