Which power supply?

[dpk33]

So I'm building my friend a system, using an overclocked Phenom II 965 system. I'm recycling parts from his old rig. There's a seasonic 520 watt psu from there.

Okay so basically, here are the specs:
Phenom II 965 be at 4.0 ghz 1.55volts
2x ATI Radeon 4890 1gb video cards
1 HDD
1 optical drive
890fx-gd65 motherboard

What power supply would allow him for this 4890 crossfire? Would the 520 watt cut it?

 

[TemjinGold]

I think the 520 would work but it would be scary. He should probably get a nice 750 watt unit.

 

[fffblackmage]

It should work, but like TemjinGold said, that's scary. Be extremely cautious, overclocking will increase power consumption very quickly.

 

[dpk33]

So would that be cutting it real close or is it fine? I'm assuming scary is fine, but I should keep an eye on things. The CPU is expected to run at 1.55 volts.

EDIT: what about an antec earthwatts 650w?

 

[fffblackmage]

Well, to give you a better idea...

I have a pretty similar rig. An unlocked Phenom II X2 550 BE and a 4890 (used to). I overclocked my 550 to 3.6GHz with 1.5V and the 4890 just past 1GHz with some stupid high voltage I don't remember.

I was just trying to see what kind of max power consumption my rig could possibly use. I ran 4 threads of Prime 95 and Furmark. My Kill-A-Watt meter showed that I was hitting around 500W from the wall (not PSU's power output). The PSU's power output was probably closer to 400W, assuming 80%-ish efficiency. I still had some headroom, but there probably isn't enough room for another 4890 at that point. Without overclocking, I was looking at 400W from the wall, at most. There's definitely room for another 4890 in that case.

Basically, as long as you're not overclocking the 4890s, you should be ok, but I'd think about reducing the cpu's overclock, especially the voltage, to ensure power consumption isn't absurdly high.

 

[dpk33]

so i assume 650 watts will be enough to support an oc'ed phenom ii and 2x 4890s? also, is it fine to use molex to pci-express power connectors for one of the cards, since the psu only has 2x 6 pin pci-e power connecters, but 4 are required.

 

[lehtv]

Yeah, 650W is just about enough. I'd be more comfortable on a 750W unit though. If buying a new PSU, you should really take a look at 750W units.

If the PSU has a single powerful +12V rail, you should be OK with using adapters.

 

[BoomerD]

If the CPU wasn't overclocked, he'd be fine.

His system would draw somewhere in the 420-440 watt range. Overclocking does increase the demand by quite a bit though.

I'd recommend a GOOD QUALITY 650-750 watt PSU. (cheap, crappy PSU's need not apply)