Radeon 4870 and powersupply


Nov 9, 2009
hi im in the process of my first build and have a few questions...

if i get an xfx radeon hd 4870 1g, do you think a corsair 400w would be ok..

itll be on a gigabyte 790gx mobo, phenom ii x3 720BE, and WD caviar black 640g hdd. this will all be in an antec 900(4 fans)

i do plan on overclocking and eventually adding an additional 4870.

i guess what im asking is.... would the 400w be enough and is it capable of powering another card in the future. ive been reading how the card requires two 6-pin slots but am unsure which psu will work with this.... plus another in the future.

im on a budget but will wait and save if it means a better computer... just nothing overkill

thanks alot


With your system and one 4870, the Corsair 400w might squek by - but I would not chance it. It is not a good idea to be pushing the max on a PSU - you get better efficiency at a lower level. Also the PSU has only on PCIe connector, although you could use two of the peripheral connectors with an adapter to power the second.

For one 4870 I recommend at least 500w and for two 700 to 750w.

Here is a site with a power calculator that you can plug in your system data and get a read on your requirements - and also use it to model future upgrades and what they might require.


Also I picked a 4870 at random - the XFX - and their stated minimum requirement is 450w.



A 400 watt Corsair PSU will power the first HD 4870 but not the second one. Since that is a future endeavor anyway, get a new PSU to go along with the second card when that day comes.

I'd recommend 650+ watts for both. Corsair, Seasonic or PC Power & Cooling (all the same thing actually) are the recommended brands.
A 400W supply MAY be enough to run it with a single 4870, but I personally wouldn't try it. That card is a big power consumer and you're likely to be pushing the limit.

You definitely will not be OK with two 4870's on a 400W supply, and I wouldn't overclock a single one on it either.

I also doubt that a 400W power supply is going to have enough connectors to power twin 4870s, maybe not even one. The 4870 takes two 6-pin PCIE connectors, and most smaller power supplies either have one 6-pin connector or none at all. So if you think a second card is in your future, best to go ahead and get a better power supply now.

Basically, if you're going to be building a machine to be a graphical powerhouse, the power supply is one thing you do NOT want to skimp on. I own a 4870 and wouldn't feel comfortable crossfiring two of them without 600 watts at a bare minimum, probably 700+ to give some breathing room.


Dec 6, 2007
breatheasy9er, I have a simular system to what you are planning. make sure that any PSU you get has the correct power pulgs to support two GPUS if you think that you are going that way. I have two 4870s. I like mine but get the 4890s or a 5850 if you can find one. I have a corsair 750watt but now wished I had a corsair 850watt. Yes 750 should be enough even as the unit ages, sometimes I feel that it labors. Get the Phenom 2 955 be they are priced very well and I don't think you'll be disappointed. Check out this link for a PSU calculator. Take into consideration fans and capacitor aging.



google corsair tx650. that should be good enough.

just built a new i7 rig for my friend + 5870 on it. and its cheaper than its modular brethren the hx620. bang for the buck wise (since you already had considered corsair), you cant go wrong with the tx650.



What?! You were using another forum? Turncoat. Traitor. Just kidding. Cross fertilization is usually good.

Well lets see how their advice stacks up. Read this review on their recommended PSU - it doesn't even have Active PCF - the article explains that. . I suggest you look at this review – at least the first page and the conclusions on the last.


Definitely a thumbs down. Power supply quality is important and often underrated.

I would stick with the Corsair 750w at $90 – really a good price for a great PSU

I was going to recommend a lower cost alternate - the OCZ StealthXStream 700w for $60 AR - but it only has 2 PCIe connectors instead of four. Here is the link just for reference.

Did you run the power calculator and what did it say for two 4870s in your system?
I generally lean towards an Antec SG-850, Antec CP-850 (only fits 3 cases) or Corsair HX-850 in a twin GFX card setup w/ OC'ing. As GFX cards get more efficient, may drop that down a bit.

here's a calculator you can use.


The silentpcreview site referenced by RJ is a great source of info.


Oct 8, 2009
You can use a PSU with only one set of PCI connectors as long as all your drives are sata. You'll need 4 molex and 2 molex to pci adapters that take 2 molex each. Many 4870 boards come with the molex adapter or you can buy them for like $5 each. I guess if your PSU has more than 4 molex connectors, you may be able to get it working with some non sata devices. It may be kind of a pain to get all the connectors within reach of where you need it, so it would be better to start out with a PSU with 4 pcie connectors.

I believe the 4870 uses about 100 watts, so I think all you would need is a 600w PSU for xfire. The more the better.