Stable Overclock: Graphic Cards Using Direct Power Link vs Board Powered

I am in the process of creating my first assembled PC ever. This is going to be a 2600K based PC with reasonable OC air-cooled for 24x7 reliability. This PC will also drive upto 6 separate 1080p monitors (4 x 24", 3 x 23"); no gaming just charting.

I am converging towards using 2 HD5670 cards. These cards do not require a dedicated PSU connection and pull the power from the Motherboard.

The other option is to move up a bin and get HD57xx based cards which have a higher max power rating and require dedicated PSU connections. If and when I do decide to play a PC game, the higher rated cards with Crossfire will be nice to have.

From the point of view of a stable over-clock, which is better?

Do the card with the separate PSU plug draw ALL their power directly from the PSU plug (say 110W) or only draw the spare power (110W - 75W) from the PSU and the rest (~75W) from the motherboard?

And do two graphic cards drawing 70W each have an affect on MB stability when OCing?

I am planning to use the ASUS P57 PRO.

I just upgraded to a 2600k and P8P67 EVO. My 700W Thermaltake power supply that was fine with my previous quad cpu at 4Ghz could not supply enough power and I had all sorts of issues until I replaced the power supply.
My opinion is that if you are going to overclock you better get cards with separate power supply and a good power supply.

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Originally Posted by Nano2k

I just upgraded to a 2600k and P8P67 EVO. My 700W Thermaltake power supply that was fine with my previous quad cpu at 4Ghz could not supply enough power and I had all sorts of issues until I replaced the power supply.
My opinion is that if you are going to overclock you better get cards with separate power supply and a good power supply.

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Did you use the same power supply and graphic cards, and just changed the motherboard/CPU? Do the graphic cards have dedicated power supply plugs or use the board for power?

The challenge of course is to figure out where the problem was. Is it because the Mobo could not handle the power needs or because the PSU was getting overwhelmed.

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Originally Posted by aviat72

Did you use the same power supply and graphic cards, and just changed the motherboard/CPU? Do the graphic cards have dedicated power supply plugs or use the board for power?

The challenge of course is to figure out where the problem was. Is it because the Mobo could not handle the power needs or because the PSU was getting overwhelmed.

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The gpu's have PCIE connectors , The power supply powers everything in your rig :)

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Originally Posted by Johnny87au

The gpu's have PCIE connectors , The power supply powers everything in your rig :)

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I am not sure I understand you Johnny Down Under.

The PSU supplies power to everything. The question is the path the current takes. When driving a card without a dedicated PCIe connection, everything (<75W each) is being routed through the Motheboard's power distribution network. With a PCIe connection the power is being split; some going through the PCIe some through the MB connections.

It all boils down to the capacity of the MB to pump in the required power to the graphic cards, while maintaining clean supply to the CPU/Memory etc. Perhaps it is a non-issue because as long as the PSU is stable the MB does not introduce any additional artifacts. But then different motherboards give different OC results so clearly the MB power distribution system is a factor.


Is Punter Retiring?

It depends on the card.

Some cards pull the full allotment of power from the PCI-E connection, some only a percentage (even with the 6/8pin connector(s). nVidia's G92 based cards were a good example of this because they were actually often over the PCI-E specification for power draw over the PCI-E slot, which is why they had some issues early on with not working with some boards and power supplies (Antec 1000w for example).

I'd suggest you get the 5770's if you intend on gaming as they would provide a better experience if you use more than one monitor in your gaming ;)

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Originally Posted by STEvil

It depends on the card.

Some cards pull the full allotment of power from the PCI-E connection, some only a percentage (even with the 6/8pin connector(s). nVidia's G92 based cards were a good example of this because they were actually often over the PCI-E specification for power draw over the PCI-E slot, which is why they had some issues early on with not working with some boards and power supplies (Antec 1000w for example).

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Thanks. That helps. So even a dedicated PSU connection will not eliminate the Mobo power draw.

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I'd suggest you get the 5770's if you intend on gaming as they would provide a better experience if you use more than one monitor in your gaming ;)

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It is a battle between the heart and the mind right now. Heart says 2x5770 but mind says 2x5670. If the 5770 were drawing all their power from the PSU then it would have been enough justification for the heart to convince the mind. The goal of course is to have a stable 24x7 OC with the ability to drive 6 1080p monitors. But right now the mind is winning since the heart has not been able to provide a solid technical reason to go 5770.

5770's would pull less power from the PCI-E motherboard slots than the 5670's would probably.

Here's some 5750 vs 5670 numbers, 5750 it easily beats it so 5770's would be a trouncing ;) : http://www.hardwarecanucks.com/forum...-review-9.html

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Originally Posted by STEvil

5770's would pull less power from the PCI-E motherboard slots than the 5670's would probably.

Here's some 5750 vs 5670 numbers, 5750 it easily beats it so 5770's would be a trouncing ;) : http://www.hardwarecanucks.com/forum...-review-9.html

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2x5670 == 1x5770. It is just that I have not played any game for 12 years :). Not sure I will either.

Can you point me to some resource which will give the specifics on the power pull?