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Need to purchase a new power supply with 2 6 pin PCI-E adapters

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February 21, 2012 10:46:30 PM

It's a sign that it's been a long time since I assembled a PC when I was surprised to discover upon unpacking my new fancy graphics card to power my new gaming PC that I needed to consider having adapters on the power supply to power it. A quick look at the available adapters on the power supply that came with my barebones kit reveals that the power supply that came with it doesn't have any 6 pin PCI Express power adapters or enough Molex adapters that could be converted to PCI Express adapters. Curses!

So now this means ordering another power supply and waiting for it to arrive.

The video card: XFX HD-687A-ZHFC Radeon HD 6870 900M Video Card

Recommends a 550W minimum power supply.

The kit: MSI H61 Intel Core i5 Barebone PC

Minimum needs:

1 24 pin adapter for the motherboard power
1 4 pin adapter for the CPU
2 SATA power adapters for the hard disk and the DVD drive
2 6 pin PCI-E adapters for the video card

Any guidance that folks can offer would be greatly appreciated.
a c 155 ) Power supply
February 21, 2012 11:22:01 PM

The link you sent for the kit appears to show a system with a 350W PSU. If that's the case, (1) it's not going to be adequate for the HD 6870 gaming at high stress levels. (2) That probably explains why the PSU doesn't have the necessary connectors; it isn't designed for that much output. I would recommend replacing the PSU with a good quality 500+W unit.
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a c 1195 ) Power supply
February 22, 2012 2:10:27 AM

The 350 Watt PSU that came with your PC has a +12V rail that has insufficient capacity to power a Radeon HD 6870.

For a system using a single Radeon HD 6870 graphics card AMD specifies a minimum of a 500 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 30 Amps or greater and have at least two 6-pin PCI Express supplementary power connectors.

The XFX Core Edition PRO550W (P1-550S-XXB9), with its +12 Volt continuous current rating of 44 Amps and with one 6-pin and one (6+2)-pin PCI Express supplementary power connectors, is more than sufficient for your build.

Total Power Supply Wattage is NOT a crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important.

Newegg.com: $69.99 ($54.99 after mail-in rebate card)

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
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February 22, 2012 3:21:01 PM

Best answer selected by Shallow Hal.
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February 22, 2012 3:22:11 PM

Thanks to everyone who replied to my question. I learned a lot just reading this thread.
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a c 155 ) Power supply
February 22, 2012 6:40:26 PM

ko888 said:
The 350 Watt PSU that came with your PC has a +12V rail that has insufficient capacity to power a Radeon HD 6870.

For a system using a single Radeon HD 6870 graphics card AMD specifies a minimum of a 500 Watt or greater power supply. The power supply should also have a combined +12 Volt continuous current rating of 30 Amps or greater and have at least two 6-pin PCI Express supplementary power connectors.

The XFX Core Edition PRO550W (P1-550S-XXB9), with its +12 Volt continuous current rating of 44 Amps and with one 6-pin and one (6+2)-pin PCI Express supplementary power connectors, is more than sufficient for your build.

Total Power Supply Wattage is NOT a crucial factor in power supply selection!!! Total Continuous Amperage Available on the +12V Rail(s) is the most important.

Newegg.com: $69.99 ($54.99 after mail-in rebate card)

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

I have a question... how did you determine the HD 6870 requires 30A at +12V? A 30A circuit would require #10 AWG wire. I don't think I've ever seen a PSU with that size conductors. Are you going by 30A X 12V = 360W?
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a c 1195 ) Power supply
February 22, 2012 6:58:13 PM

clutchc said:
I have a question... how did you determine the HD 6870 requires 30A at +12V? A 30A circuit would require #10 AWG wire. I don't think I've ever seen a PSU with that size conductors. Are you going by 30A X 12V = 360W?

Read more closely.

The power supply +12V current recommendation is for the system not just the Radeon HD 6870.

The Radeon HD 6870 itself can draw over 14 Amps if you were to run Furmark or OCCT GPU stress testing.

You will still need to power the CPU which also obtains all of its power from the +12V rails, the motherboard chipset, hard disk drive motor(s), optical disk drive motor, CPU cooling fan(s), case cooling fans, ...

The 30 Amp recommendation for the +12V rail(s) will safely handle all of that.
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February 22, 2012 7:14:00 PM

ko888 said:
Read more closely.

The power supply +12V current recommendation is for the system not just the Radeon HD 6870.

The Radeon HD 6870 itself can draw over 14 Amps if you were to run Furmark or OCCT GPU stress testing.

You will still need to power the CPU which also obtains all of its power from the +12V rails, the motherboard chipset, hard disk drive motor(s), optical disk drive motor, CPU cooling fan(s), case cooling fans, ...

The 30 Amp recommendation for the +12V rail(s) will safely handle all of that.


Speaking as someone who has never been very comfortable figuring out electrical requirements, I'm also curious to learn how you determine what the amp requirement is for all the different components of the system.
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a c 1195 ) Power supply
February 22, 2012 7:17:16 PM

Shallow Hal said:
Speaking as someone who has never been very comfortable figuring out electrical requirements, I'm also curious to learn how you determine what the amp requirement is for all the different components of the system.

I can only speak for myself. I took Electrical Engineering and Computer Science when I went to university.
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February 22, 2012 7:22:44 PM

ko888 said:
I can only speak for myself. I took Electrical Engineering and Computer Science when I went to university.


Well, I majored in Economics, so that goes to show you why I'm the one asking questions and you're the one answering them. :) 
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a c 1195 ) Power supply
February 22, 2012 7:25:18 PM

Shallow Hal said:
Well, I majored in Economics, so that goes to show you why I'm the one asking questions and you're the one answering them. :) 

Well I also have a degree in Economics too. Got it before my Computer Science degree.
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February 22, 2012 8:46:03 PM

So you can tell us which PSU to buy and why it is priced the way it is? :na: 
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a c 155 ) Power supply
February 22, 2012 9:18:58 PM

ko888 said:
Read more closely.

The power supply +12V current recommendation is for the system not just the Radeon HD 6870.

The Radeon HD 6870 itself can draw over 14 Amps if you were to run Furmark or OCCT GPU stress testing.

You will still need to power the CPU which also obtains all of its power from the +12V rails, the motherboard chipset, hard disk drive motor(s), optical disk drive motor, CPU cooling fan(s), case cooling fans, ...

The 30 Amp recommendation for the +12V rail(s) will safely handle all of that.

Explanation accepted, and properly chastised. Now would you be kind enough to tell me how to determined the current draw of the HD 6870? Or any other card for that matter. Since there is no place I know of where the impedance of the card is listed, I can't use Ohm's Law.
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a b ) Power supply
February 22, 2012 11:31:23 PM

This topic has been closed by Mousemonkey
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