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Dual GPU/Single Card Questions

post #1 of 3
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Heya everybody, got a few questions for ya.

I'm curious, because I hear that Crossfire/SLI doesn't always work in windowed mode and will generally grab just 1 card to do the rendering.

If I had a dual GPU, single card like the GTX 590, HD 5970 or HD 6990, would it only let 1 of the GPUs on the card do the rendering, or would they both work?

Also, do dual GPUs have more problems, less problems, or same problems as a dual card set up in SLI/Crossfire? Like would I have the same amount of problems doing 2 GTX 560 ti's as I would with a single GTX 590?

If a game has issues with Crossfire/SLI, could you disable a GPU to force it to run like a single GPU card or is it always dual GPU?

Although there are 2 GPUs on a single card, will a CPU still be a bottleneck in some cases, or is that only if there's more than 1 physical card?

What seems to have less problems with a dual GPU set up: Nvidia or AMD? I'm not asking about more frames or a better score in 3d Mark, I'm wondering about PROBLEMS, like drivers failing, games not recognizing the card, etc.

Thanks!
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post #2 of 3
Dual gpu cards act as one card and you cannot disable a core and have the other going. Dual gpu cards have the same problems as a dual card setup but also some others. Of course if a game has poor crossfire/sli support like crysis 2 (huge microstutter which is basicly were you can see the change in gpu frames.. Just incase you didnt know crossfire/sli works by having the frames altinate from each gpu core so card 1 would do the first frame, card 2 the 2nd frame, card 1 the 3rd frame and so on) you can simply disable crossfire/sli by stopping the 2nd card from working with the first.

Now this is the big issue with dual gpu cards, i said that you cant disable one gpu and have the other on (disable crossfire/sli) so you end up like many with dual gpu cards not being able to play games with poor crossfire/sli support.

The bonus of having two cores on a single card is the gain in performance, and the less power usage therefore less heat.

Personally id say if you can afford to get two single cards then do that but others say different.
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post #3 of 3
In the AMD control panel, if you opt to disable Catalyst AI, that will disable Crossfire on a dual GPU card. The primary GPU then assumes the full 3D rendering duties. At least, this was true when I had my HD5970, so I am not sure if anything has changed since then. I'm not sure how it would work with Nvidia's control panel though, so maybe someone with a GTX 295 or GTX 590 can chime in.

However, last I remembered, both Nvidia and AMD have been making strides towards keeping SLI/Crossfire enabled in window mode - with AMD having the better implementation. But I think it may depend on the game or application you are using, as you suggested.

The question of whether a dual-GPU single card having more or less problems than two single GPU cards is complicated. When I had my HD5970, I seemed to run into more problems frequently compared to owners who had two HD5850/70's. It is just my belief that when it comes down to power delivery, two cards with dedicated circuitry are going to be much stable and reliable in general, at the cost of higher power consumption.

As far as CPU bottlenecks go, generally, the higher the CPU overclocks, the better your performance will be as you increase your GPU count. There is certainly a good amount of overhead that needs to be overcome as the GPU's increase, however, most modern CPU's won't run into much trouble running two GPU's though. At three or more, you would most certainly need a very fast CPU in order to keep up.

As for the state of current drivers, I think both are about equal. I had heard about Nvidia drivers being superior to AMD's for a long while, but since migrating over I have had just as much trouble, which really isn't that much at all. For the most part, when games have been released for some time, the drivers will have caught up with improved profiles so it doesn't really matter right now.

Your choice really should come down to how much you want to spend, and will your current rig support it.
     
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