Why do i need an 850w PSU to power SLI/CF

[Pandamonia]

A few points:

Power supplies tend to be most efficient in the middle of their range. Ideally you want to be drawing about half of the max rating.

http://www.overclock3d.net/gfx/articles/2006/11/22163203695l.jpg

I looked up that article and near as I can tell the Unigine's Heaven Benchmark version 4.0 benchmark they ran is not a complete system stress test. It is a gaming style benchmark that simulates a gaming GPU load. It does not really stress the CPU and it does not stress the GPU as hard as something like Furmark or OCCT would. It does seem like a realistic gaming load, it is just not a max power draw stress test.

If you can afford 2x 290s or 2x 780s you can afford a new PS!

Im £1500 into a build which has cost me £2450! This was supposed to be a flutter on a few new bits of kit. Only the case is left!

 

[lakedude]

I think the 620 watt PS will be fine in the short term as long as everything is run at stock clocks/voltages and so long as you are only running "normal" loads (not Furmark, not OCCT, not Prime, not Linpack, etc.).

You might spend $20-$25 on a Kill-a-Watt to verify your load.

 

[Pandamonia]

I think the 620 watt PS will be fine in the short term as long as everything is run at stock clocks/voltages and so long as you are only running "normal" loads (not Furmark, not OCCT, not Prime, not Linpack, etc.).

You might spend $20-$25 on a Kill-a-Watt to verify your load.

Well i have 2x MSI Lightning 780's on order for tomorrow so i guess we will find out! 🙂

 

[UaVaj]

i7-4770k = 84w per intel
SSD = 3w average
2 stick ddr3 = 6w average
mb = 35w average
2 780 = 250w per NVidia

628w max. cutting it close, but you should be fine (YMMV). keep us posted. hardware secrets shows hx620 is capable of delivery 746w and still in spec.

 

[Pandamonia]

i7-4770k = 84w per intel
SSD = 3w average
2 stick ddr3 = 6w average
mb = 35w average
2 780 = 250w per NVidia

628w max. cutting it close, but you should be fine (YMMV). keep us posted. hardware secrets shows hx620 is capable of delivery 746w and still in spec.

I have the AX860 coming 🙂

Now i just need to close some deals this week to pay for it all! 😀

 

[Makaveli]

I have the AX860 coming 🙂

Now i just need to close some deals this week to pay for it all! 😀

good choice quality brand and 7 year warranty 🙂

 

[coffeejunkee]

Well i have 2x MSI Lightning 780's on order for tomorrow so i guess we will find out! 🙂

I have the AX860 coming 🙂

Now i just need to close some deals this week to pay for it all! 😀

AX860 is a great psu ofc but are you going to try with the HX620 too or not?

Anyway, if it's true that running a psu close to max output will kill it quick like some people claim then I guess Apple is in for a nasty surprise. 12-core cpu + 2 heavy duty ws cards on a 450W psu...

 

[Pandamonia]

AX860 is a great psu ofc but are you going to try with the HX620 too or not?

Anyway, if it's true that running a psu close to max output will kill it quick like some people claim then I guess Apple is in for a nasty surprise. 12-core cpu + 2 heavy duty ws cards on a 450W psu...

I think its all BS personally.

Someone said that 620w is rated to 724w peak.

 

[UaVaj]

here you go. HX620 delivering 746w (901w from the wall) and still in spec.

http://www.hardwaresecrets.com/article/Corsair-HX620W-Power-Supply-Review/371/9

 

[Makaveli]

I think its all BS personally.

Someone said that 620w is rated to 724w peak.

I think you still missed the point.

Yes the PSU might be able to hit 724w at peak load but it will not be able to sustain that indefinitely.

And with capacitor aging its the reason people tend to buy psu with alittle extra room for the future cause in 4 years of use that 620watt psu probably won't be able to hit that peak.

 

[Pandamonia]

I think you still missed the point.

Yes the PSU might be able to hit 724w at peak load but it will not be able to sustain that indefinitely.

And with capacitor aging its the reason people tend to buy psu with alittle extra room for the future cause in 4 years of use that 620watt psu probably won't be able to hit that peak.

I dont think caps wear out in short amounts of time, heck the ones on my GPU will live twice as long as me.

 

[Pandamonia]

here you go. HX620 delivering 746w (901w from the wall) and still in spec.

http://www.hardwaresecrets.com/article/Corsair-HX620W-Power-Supply-Review/371/9

I guess i was right after all!

910w at the wall!

 

[Torn Mind]

Capacitor aging causes ripple/noise to increase. As long as the proper voltage in the circuit it is used in is correct and engineers properly derate the voltage according to the conditions in the unit, you can pull as many amps as you want. When PSUs are "killed" because one pulled "too much wattage", the victim parts are the MOSFETs or Schottkey rectifiers, and JonnyGURU and Hardware Secrets have units that they have killed in this manner.