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Enough Power?

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September 19, 2011 2:07:51 AM

Is this psu
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

enough to power these in crossfire
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Rest of the computer:

Motherboard:
ASUS Maximus III Formula

CPU:
i5 760 2.8 @ 4.1

CPU Cooler
H70 Cooler

Memory:
4 gigs mushkin ddr3

More about : power

September 19, 2011 3:43:46 PM

there is a deeper issue here than just raw wattage. PSU's have rails, multi rail PSU's are best for power hungry equipment. amperage and wattage to the PCI-E cables in the PSU matters more than the raw wattage of the PSU. a PSU can be 1KW but if it supplies 11V at 15A to PCIE and a 500W PSU does 12V at 25A to the PCIE then the 500 watt is much better for the cards. a common issue with high amperage hardware is voltage drops and spikes from cards or HD's powering up. on a single rail PSU a HD turning on can cause a voltage drop for all other components in the computer. on a multi rail PSU each rail is segmented from each others voltage spikes/drops due to separate components turning on and off. while a higher wattage PSU is generally best, in my personal experience power requirements are vastly over estimated. as an example; i run 2 radeon 5870's 9 HD's and have an OC i7. the power requirements for a single 5870 is 500W but with my monitor when i max out my computer i use just under 840W of power. when selecting a PSU, ensuring it has stable power with enough amperage is the best way to ensure things work.
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September 19, 2011 4:28:40 PM

henydiah said:
power consumption gigabyte Xfire 6870 is 421, you had power 750W for OC system and crossfire
http://www.guru3d.com/article/gigabyte-radeon-hd-6870-r...

Note: 800W or above would be better

Quote:
Bear in mind that the system Wattage is measured from the wall socket and is for the entire PC


which is without efficiency factored in

so 421 watts from the wall = 336 watts drawn from the psu @ 80% efficiency

even 650 watts will run 6870 crossfire
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September 20, 2011 3:23:21 AM

As new egg does not list what the Current draw is from the the 6870. I came up with it like this:
On the link above that henydiah posted they list that at max load 1 card draws is 291W(correction) its more like 170 says Obsidian86, I was reading the Full PC's Draw... and if you are using a full 12 volts that means each card draws 24.25 14amps
(Watts=volts *amps)
So you have 2 X24.25 14amp cards = 48.5 28Amps and your PSU is listed as 54 amps on its single 12 rail.

Conclusion: 48.5 28<your 54 amps, your PSU =good

(please correct my math if I'm wrong some how)
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a b ) Power supply
a b à CPUs
September 20, 2011 4:41:13 PM

zzx said:
As new egg does not list what the Current draw is from the the 6870. I came up with it like this:
On the link above that henydiah posted they list that at max load 1 card draws is 291W and if you are using a full 12 volts that means each card draws 24.25 amps
(Watts=volts *amps)
So you have 2 X24.25 amp cards = 48.5 Amps and your PSU is listed as 54 amps on its single 12 rail.

Conclusion: 48.5<your 54 amps, your PSU =good

(please correct my math if I'm wrong some how)


1 card draw includig the whole pc

a 6870 at flat max draws 170 watts so 2 can theoretically draw 320 watts on their own which leaves you still 380 watts on a 750 watt psu

you could easily run 2 o a 650 watt psu
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a b ) Power supply
a b à CPUs
September 20, 2011 10:38:54 PM

empier1988 said:
Is this psu
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

enough to power these in crossfire
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Rest of the computer:

Motherboard:
ASUS Maximus III Formula

CPU:
i5 760 2.8 @ 4.1

CPU Cooler
H70 Cooler

Memory:
4 gigs mushkin ddr3


you will be fine, plenty of power. with an OC CPU and 6870 in CF under stress test you won't break 450w. If you OC everything you are still under 500w. during gaming you will be under those power marks.

Test System Specs
- Intel Core i7 920 (Overclocked @ 3.70GHz)
- x3 2GB G.Skill DDR3 PC3-12800 (CAS 9-9-9-24)
- Asus P6T Deluxe (Intel X58)




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