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Adding a second 6 pin PCI Express power cable to 600 watts PSU

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January 30, 2013 7:13:10 PM

Hi everyone,

I'm looking to get my hands on the HD7870-DC2-2GD5 from ASUS, and I know for a fact I need two 6 pin PCI Express power cables.

The thing is, my PSU only offers me one 6 pin PCI Express power cable.

On the other hand, I have a bunch of 4 pin peripheral power cables that are unused (I only have one hard drive and my motherboard linked to my PSU right now).

Does someone have any advice to offer ?

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OS : Windows 8 64 bit
Processor: AMD Phenom(tm) II X4 960T Processor (4 CPUs), ~3.0GHz
Memory: 4096MB RAM
Motherboard : M5A78L-MLX3

Here are pictures of my PSU with all the specs on it.




Best solution

a b ) Power supply
January 30, 2013 7:40:58 PM
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That is a very cheap PSU that I wouldn't trust to run that card.
http://www.cuttingedgecomputers.ca/shopexd.asp?id=605

An actually good PSU that is only 500W is more than powerful enough but that I doubt will be able to output over 375W.
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

If you do want to continue using the crappy PSU you can but it has a high chance of failing and taking much more expensive parts with it.
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January 30, 2013 7:44:02 PM

That's interesting ... I just had to change my motherboard (M5a78LM-LX Plus) because it was fried. Maybe the HD 4770 was drawing too much power for that PSU ...
a b ) Power supply
January 30, 2013 7:45:53 PM

I don't think that was the issue with the motherboard since normally the PSU won't work at all and it'll go down in sparks.
http://www.youtube.com/watch?v=JP8nFQYQW34

Some are worse than that when they die.
January 30, 2013 7:48:30 PM

What's probably happening is the power from your power supply is jumping up and down and not staying at a steady rate which can cause parts to fail. This is why you need an 80+ bronze/silver/gold/platinum power supply if you want to be able to do anything with your computer. If you had a 600watt 80+ psu, you could power 2 7870s just fine but with yours you would be running into a wall with your current one.
January 30, 2013 7:53:21 PM

Quote:
Welcome to Tom's Hardware Forums!


Your 600 watts PSU with 26A on the 12V rail is adequate for the Graphics card. In this case you can use a splitter.


Try something like this: http://www.newegg.com/Product/Prod [...] 6812198016


[...]

Thank you Ubrales.

Does that mean the method suggested here (http://www.tomshardware.com/forum/279391-28-power-requi...) to calculate the 12V amps requirements for GPU is wrong ?

It suggested that ''To figure out how many amps you need on the 12 volt rail use this formula (watts / 12 = amps) so if the card requires 650 watts simply divide 650 by 12. This formula only works for 12 volt for different voltages there are different dividers. '' ( SAAIELLO ).

Following this guide, I would actually need 41 amps for the 12V rail. Or am I wrong somehow ?

The HD 7870 needs 500 watts of power (http://www.amd.com/fr/products/desktop/graphics/7000/78...).
a b ) Power supply
January 30, 2013 7:58:06 PM

This is the most accurate PSU calculator I've found.
http://www.extreme.outervision.com/psucalculatorlite.js...
I have the pro version so I can tell you the amps if you really need to know.

The 7870 doesn't actually use 500W of power they just recommend that as overkill so if people are running like 8 hard drives and lots of other accessories the computer will be fine.
a b ) Power supply
January 30, 2013 8:04:34 PM

Djak372 said:
Quote:
Welcome to Tom's Hardware Forums!


Your 600 watts PSU with 26A on the 12V rail is adequate for the Graphics card. In this case you can use a splitter.


Try something like this: http://www.newegg.com/Product/Prod [...] 6812198016


[...]

Thank you Ubrales.

Does that mean the method suggested here (http://www.tomshardware.com/forum/279391-28-power-requi...) to calculate the 12V amps requirements for GPU is wrong ?

It suggested that ''To figure out how many amps you need on the 12 volt rail use this formula (watts / 12 = amps) so if the card requires 650 watts simply divide 650 by 12. This formula only works for 12 volt for different voltages there are different dividers. '' ( SAAIELLO ).

Following this guide, I would actually need 41 amps for the 12V rail. Or am I wrong somehow ?

The HD 7870 needs 500 watts of power (http://www.amd.com/fr/products/desktop/graphics/7000/78...).

Please read under details here: http://www.newegg.com/Product/Product.aspx?Item=N82E168...

What it really means that you need a total system power of at least 500 watts; not 500 watts just for the Graphics card.

For calculations for DC circuits is fine - E x I = Watts (E = Volts, I = current in Amps)

I agree with the other posters in that the PSU is the heart of the system and you need a high quality ROBUST (adjective) power supply.

Good brands are Corsair, Seasonic, and Antec that I know of. There are others too but these brands come to mind. Watch for promos and sales at Newegg and pick up a good 600 watts or higher PSU depending on the sale price.
January 30, 2013 8:16:50 PM

Wow. I am impressed by the short time it took for the answers and by the quality of them.

I actually never checked what that PSU was worth but now that I know it is sold for 26.99 $, and that it seems to be some obscure and unknow brand I will definitely buy a new one from one of the brands you mentionned.

Thank you very much for the advice !
January 30, 2013 8:17:24 PM

Best answer selected by Djak372.
a b ) Power supply
January 30, 2013 8:21:10 PM

You're welcome, I'm glad I could help.
!