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Will 550watts be enough for crossfire 7870

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  • Power Supplies
  • Crossfire
  • Components
Last response: in Components
January 28, 2013 1:32:14 AM

Hi, I'm wondering if 550watts psu will be enough to crossfire 7870 or not.
How much watts will you recommend if it isn't? Thanks in advance

More about : 550watts crossfire 7870

January 28, 2013 1:39:34 AM

It depends on the rest of your computer, hun. A good 550Watt (something from Corsair or Seasonic) should be fine.

If you are buying a new one, I'd pick up a slightly larger one, like a Corsair 700watt, just for efficiency and overclocking headroom on parts. But 550watt will run that GPU fine.

Just a note: it's very important to get a good quality PSU. No-name brands and bad units can damage your parts, degrade rapidly over time and perform poorly. A good quality PSU is very important.
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a b ) Power supply
January 28, 2013 1:43:13 AM

It depends on what are the rest of the components.

Crunch ur numbers here http://www.extreme.outervision.com/psucalculatorlite.js...
Make sure u look into capacitor aging as well.

One thing to look out for is to check whether ur current psu or the new psu that u gonna buy have enough PCI-E power conenctors to support both cards.
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a b ) Power supply
January 28, 2013 1:53:39 AM

a good 550w PSU from a good brand is fine, even when you OC the CPU and GPU, assuming you're not adding a whole lot of other components in the future, i.e dozens of HDDs.

only grab a 700w if you're planning it to run in crossfire. there's nothing efficient about a 700W PSU on a PC using up only 400-500W for all it's lifetime. heck, you're wasting electricity bills in that case, seeing as you're not pushing it at it's recommended load for 80+ efficiency to take effect.

EDIT: ^took a quick look around extreme outervision's PSU calculator linked above. got 540W, and that's after i put a 7950, a 3570K at 4.4ghz @ 1.3V (not that you'll ever need that much Vcore, most likely), 3x high rpm HDDs, a couple of USB devices, 2x LED 120mm fans, 2x high performance 120mm fans, a PCIE 1x device and capacitor aging at 30%. i should also note the website tends to over estimate the amount a bit. and again, that's at the worst (best?) case scenario.
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January 28, 2013 1:57:24 AM

Hazle said:
a good 550w PSU from a good brand is fine, even when you OC the CPU and GPU, assuming you're not adding a whole lot of other components in the future, i.e dozens of HDDs.

only grab a 700w if you're planning it to run in crossfire. there's nothing efficient about a 700W PSU on a PC using up only 400-500W for all it's lifetime. heck, you're wasting electricity bills in that case, seeing as you're not pushing it at it's recommended load for 80+ efficiency to take effect.

That's not how PSU's work. Almost all units are most efficient at 50% load -- meaning they deliver the most power with the least wastage.



The 80+ means they don't drop below 80% efficiency -- ever. Not that they are best at 80% load.
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January 28, 2013 8:32:54 AM

Thanks for all the answer guys :) 
My other specs are
I5 3570 3.4ghz
Gskill 8gb 1600mhz
I have the Antec Vp550p according to reviews it's almost a 80+ bronze psu.
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a b ) Power supply
January 28, 2013 8:38:01 AM

I wouldn't be surprised to see instability under load.
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a c 502 ) Power supply
January 28, 2013 1:06:58 PM

paul2955tw said:
Hi, I'm wondering if 550watts psu will be enough to crossfire 7870 or not.
How much watts will you recommend if it isn't? Thanks in advance


Hi - realhardtech recommends 600w to CF a system
with 2 7870's. That means you could "get by"
with a quality 550w unit as they and the PSU
calculators build in xtra to allow for among other
things PSU that don't deliver their published
specs and there are a lot of em out there.

Also, if you don't want to be using molex
to PCI-E adapters, you need to look for a
quality PSU that has 4 PCI-E adapters as
7870's require 2 each. Generally, you start
to see PSU's with 4 PCI-E connectors at
650w & above.

Also, a note regarding another post. Very often
there is an efficiency benefit to using a higher
power PSU than you need, and that is that
very often (while gaming) you will be in the
PSU's "sweet spot" efficiency range, which
is usually 40-60% of it's max output. I.E.
if you are using 325w during a CF gaming session
that would be 50% of a 650w unit's max, and
most likely it's most efficient range.

Tom

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a c 502 ) Power supply
January 28, 2013 1:16:33 PM

Hazle said:
a good 550w PSU from a good brand is fine, even when you OC the CPU and GPU, assuming you're not adding a whole lot of other components in the future, i.e dozens of HDDs.

only grab a 700w if you're planning it to run in crossfire. there's nothing efficient about a 700W PSU on a PC using up only 400-500W for all it's lifetime. heck, you're wasting electricity bills in that case, seeing as you're not pushing it at it's recommended load for 80+ efficiency to take effect.

EDIT: ^took a quick look around extreme outervision's PSU calculator linked above. got 540W, and that's after i put a 7950, a 3570K at 4.4ghz @ 1.3V (not that you'll ever need that much Vcore, most likely), 3x high rpm HDDs, a couple of USB devices, 2x LED 120mm fans, 2x high performance 120mm fans, a PCIE 1x device and capacitor aging at 30%. i should also note the website tends to over estimate the amount a bit. and again, that's at the worst (best?) case scenario.



Not true. Per jonnyguru:
Is there such a thing as "too much power"?

Generally, no. A power supply only puts out as much power as needed by the system's components. In some cases, an 800W power supply may actually use less power from the wall than a 500W power supply, depending on the efficiency of the units. Often times, buying an "oversized" PSU is a good choice due to it's ability to perform even under higher temperatures, a quieter fan because the unit is delivering a lower percentage of it's total capability and considerable system upgradability without having to worry about having enough power when upgrading a graphics card, adding a graphics card for SLI or additional hard drives.

Tom
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January 28, 2013 1:23:08 PM

toyftw said:
Hi - typo i think? Should be efficient, right?

Tom

That was a test! You passed.

>_>

<_<
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a c 502 ) Power supply
January 28, 2013 1:53:13 PM

MatildaPersson said:
That was a test! You passed.

>_>

<_<



LOL!
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Best solution

a c 1669 ) Power supply
January 28, 2013 3:55:03 PM

For a system using two Radeon HD 7870 GHz Edition graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 600 Watt or greater system power supply. The power supply should also have a maximum combined +12 Volt continuous current rating of 40 Amps or greater and have at least four 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most critical factor.

Overclocking of the CPU and/or GPU(s) will require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.

You may find power supplies on the market that supply more than enough Wattage to run the system. However, some of them lack Sufficient Amperage capacity on the critical +12 Volt rail, which is necessary to properly power the critical components in the system (i.e. CPU and GPUs). This is the reason why graphics card manufacturers may overstate the power supply wattage, usually by at least 50 Watts, in an attempt to take into account some of those power supplies that have the weaker +12 Volt rail(s).

The Antec VP Series 550W (VP550P), with its maximum combined +12 Volt continuous current rating of 45 Amps and with two (6+2)-pin PCI Express supplementary power connectors, is electrically sufficient to power your system configuration with two Radeon HD 7870 GHz Edition graphics cards in 2-way CrossFireX mode but it is deficient by two PCI Express supplementary power connectors so you'll have to resort to using a couple of dual 4-pin Molex peripheral to 6-pin PCI Express supplementary power adapter cables.
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January 28, 2013 11:34:33 PM

ko888 said:
For a system using two Radeon HD 7870 GHz Edition graphics cards in 2-way CrossFireX mode AMD specifies a minimum of an 600 Watt or greater system power supply. The power supply should also have a maximum combined +12 Volt continuous current rating of 40 Amps or greater and have at least four 6-pin PCI Express supplementary power connectors.

Total Power Supply Wattage is NOT the crucial factor in power supply selection!!! Sufficient Total Combined Continuous Power/Current Available on the +12V Rail(s) rated at 45°C - 50°C ambient temperature, is the most critical factor.

Overclocking of the CPU and/or GPU(s) will require an additional increase to the maximum combined +12 Volt continuous current ratings, recommended above, to meet the increase in power required for the overclock. The additional amount required will depend on the magnitude of the overclock being attempted.

You may find power supplies on the market that supply more than enough Wattage to run the system. However, some of them lack Sufficient Amperage capacity on the critical +12 Volt rail, which is necessary to properly power the critical components in the system (i.e. CPU and GPUs). This is the reason why graphics card manufacturers may overstate the power supply wattage, usually by at least 50 Watts, in an attempt to take into account some of those power supplies that have the weaker +12 Volt rail(s).

The Antec VP Series 550W (VP550P), with its maximum combined +12 Volt continuous current rating of 45 Amps and with two (6+2)-pin PCI Express supplementary power connectors, is electrically sufficient to power your system configuration with two Radeon HD 7870 GHz Edition graphics cards in 2-way CrossFireX mode but it is deficient by two PCI Express supplementary power connectors so you'll have to resort to using a couple of dual 4-pin Molex peripheral to 6-pin PCI Express supplementary power adapter cables.

wow thanks for the detailed reply :)  So if I do crossfire 7870 will I still be able to overclock the cpu and the gpu?
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a c 1669 ) Power supply
January 29, 2013 2:41:28 AM

paul2955tw said:
wow thanks for the detailed reply :)  So if I do crossfire 7870 will I still be able to overclock the cpu and the gpu?

If you keep the CPU overclock to a max of 4.5 GHz or lower you should be safe.

The extra power consumption required when overclocking a Radeon HD 7870 GHz Edition varies depending on brand and specific model. There should be enough remaining capacity on the +12V rail to handle some overclocking of the 2-way CrossFired Radeon HD 7870 GHz Edition graphics cards.
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January 29, 2013 3:25:58 AM

I have the MSI hawk, what about those? Also, if I use the adapters will there be any difference as compared to PCIE cables from the power supply?
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a c 1669 ) Power supply
January 29, 2013 4:50:44 AM

paul2955tw said:
I have the MSI hawk, what about those? Also, if I use the adapters will there be any difference as compared to PCIE cables from the power supply?

Overclocking both MSI Radeon HD 7870 HAWK graphics cards will require an extra ~3 Amps from the +12V rail(s).

Connector distribution on the Antec VP Series 550W (VP550P) PSU's two +12V rails doesn't look good.

+12V1 ATX, PCIe1, PCIe2, Peripheral, SATA

+12V2 EPS (i.e. CPU only)

If you use two adapter cables they will be using the peripheral connectors that are already on the same +12V1 rail as the two PCI Express supplementary power connectors. That would definitely overload and trigger the PSU's Over Current Protection (OCP) circuit and shutdown the PSU.

You will need a new power supply because you can't work around this problem.
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January 29, 2013 9:19:10 AM

ko888 said:
Overclocking both MSI Radeon HD 7870 HAWK graphics cards will require an extra ~3 Amps from the +12V rail(s).

Connector distribution on the Antec VP Series 550W (VP550P) PSU's two +12V rails doesn't look good.

+12V1 ATX, PCIe1, PCIe2, Peripheral, SATA

+12V2 EPS (i.e. CPU only)

If you use two adapter cables they will be using the peripheral connectors that are already on the same +12V1 rail as the two PCI Express supplementary power connectors. That would definitely overload and trigger the PSU's Over Current Protection (OCP) circuit and shutdown the PSU.

You will need a new power supply because you can't work around this problem.


Thanks, it helped me out a lot :) 
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January 29, 2013 9:19:49 AM

Best answer selected by paul2955tw.
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