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I have 2 graphics cards, one onboard and one dedicated, both Nvidia. I want to know if I can run both graphics cards at same time, connected to a single monitor, in order to get mixed performance. Is there any way to do this? What should I set in BIOS and where should I connect the VGA port?

Onboard graphics card: Nvidia Geforce 7050 256mb DDR1

Dedicated graphics card: Nvidia Geforce 8400 GS 512mb DDR2

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What you're trying to do (I think) is called Hybrid Crossfire on ATI/AMD graphics cards (…), and to my knowledge there's no Nvidia equivalent. – Marcus Chan Feb 3 '13 at 9:49
Mods, I would vote to unclose this if I could, since it's obvious that it's not a duplicate of the linked post. – Marcus Chan Feb 3 '13 at 9:50
Hey marcus!! so it is possible to do Hybrid crossfire but unfortnately for ATI/AMD only..anyway thankyou v much! – gaurav jakkal Feb 5 '13 at 8:52… - this would be your solution if you were willing to get a new motherboard. – Enigma Feb 6 '13 at 19:53
Ok, I was wrong, there is an Nvidia equivalent. See my answer below. – Marcus Chan Feb 7 '13 at 4:44

In fact, the answers that say there's no Nvidia Crossfire equivalent are wrong. However, the GeForce 7050 motherboard GPU described in the question is too old to support it (and it wasn't a very successful technology anyway). It's called Hybrid SLI, and this article describes it in some detail. It has 2 modes: one like Optimus to save power, and one to increase performance.

NVIDIA Hybrid SLI Ready Motherboards:

  • nForce 720a MCP
  • nForce 730a MCP
  • nForce 750a SLI MCP
  • nForce 780a SLI MCP
  • GeForce 8100 motherboard GPU
  • GeFOrce 8300 motherboard GPU
  • GeForce 8200 motherboard GPU

The GPU in question would be on a 610i or 630i chipset (source), so it's not supported.

+1 @Enigma and @JourneymanGeek, Your answers are good except that they're both technically incorrect. And as for the other suggestions, Lucid Virtu is pointless since replacing the mobo in this case would get rid of the mGPU the OP is trying to use as a boost, Lucid Hydra is for mixing PCIe GPUs (not a PCIe and a mobo), and Optimus is for saving power not boosting graphics (as well as having the same issue as Virtu).

@Enigma as Journeyman Geek pointed out, no, I don't think you can run dual monitors with a mGPU that old.

tl;dr: You can't run these two GPUs at the same time, but not for the reasons in the other two answers.

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Oh, the crux of my answer was that it wasn't possible - but if someoneone was to do that, those technologies were the ones that he'd want to look at. I can't think of any way to do switchable graphics with arbitrary hardware, but those combinations are things that might work – Journeyman Geek Feb 7 '13 at 6:51
My older and lesser AMD chipset motherboard is capable of running dual monitor split GPU's ( Curiously enough, the spec sheet doesn't list any specific nvidia chipset, just an AMD 770. I'll have to look into that more. It is dependent on the bios settings/capability and I can, from within bios, disable or enable this functionality. Good thorough answer nevertheless. – Enigma Feb 7 '13 at 14:58
It's ATI, not nvidia. – Enigma Feb 7 '13 at 15:07
Oh, hmm. doesn't list a mGPU, that's weird. – Marcus Chan Feb 7 '13 at 18:46
If an answer (probably this one) is adequate in answering your question, it's customary to select it as the answer. – Enigma Feb 9 '13 at 16:03

None of the technologies I know of at the moment can do this. There's a few that come close.

Lucid Logix Virtu would do this with a modern intel processor with a onboard graphics option, if you're running sandy bridge or Ivy bridge. Some older nvidia systems had a switchable graphics option called optimus, as well as the previously mentioned ATI/AMD hybrid crossfire option.

There's nothing I can think of that will switch graphics cards on the fly and use a specific graphics card to output even where rendering happens on the other card. Quite a few chipsets also disable onboard graphics when a discrete adaptor is installed.

Its just not possible as far as I can tell

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In many cases, one can set the graphics configuration in the motherboard to use both the onboard and pci/pcie simultaneously. – Enigma Feb 6 '13 at 18:15
depends on the motherboard. Older ones often use the same pci-e x16 channel for discrete and integrated graphics, and shuts down the integrated graphics if a card is installed in the x16 slot – Journeyman Geek Feb 6 '13 at 23:46
I'd assume he's got a fairly new one with an on-board like that. That's better than some of my georce PCI-E x16 cards. – Enigma Feb 7 '13 at 0:33
Its core2 era. Least on the intel chipsets it shared the channel – Journeyman Geek Feb 7 '13 at 1:31
Ah, I've always owned AMD chipsets - that's probably it. – Enigma Feb 7 '13 at 14:52

I did exactly what you are talking about except with two monitors. The answer is no, not without a great deal of special driver development in your specific case. SLI is meant for identical cards unless you have a special chip on your motherboard (Lucid Hydra). (Hybrid Crossfire would support something like this as several comments point out)

The main reason why SLI just supports identical cards for now anyways is because the effect of merging two GPU's would have to be handled differently for each different pair combo. There's just too many possibilities unless a sophisticated enough system is developed to dynamically merge the processing power.

You would lose CPU and/or GPU processing power on bridging the gap between the different operating modes of each GPU.

You could have a nice dual screen set up with independent cards per monitor though - Highly recommended.

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Except Crossfire actually does support something like the author wants to do. Otherwise in the Nvidia world, Optimus requires specific hardware, but if the author had that specific hardware it would be possible. – Ramhound Feb 6 '13 at 18:07
but he has two nvidia cards... no crossfire – Enigma Feb 6 '13 at 18:08
Optimus is a energy/performance optimizer based on CUDA which bridges the gap between GPU and CPU. – Enigma Feb 6 '13 at 18:19
It's also exclusively for laptops for now. – Enigma Feb 6 '13 at 18:33
I made the edit to correct the mistake (which anyone can see I realize - obviously I wasn't trying to hide it). My point is that, even while I did also bring up crossfire, it has no relevance to this question since the asker has Nvidia cards. You need a special chip on your motherboard to run SLI with different models - correct me if I'm wrong. – Enigma Feb 6 '13 at 19:42

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