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I have two cards GTX 690 (dual core). I did the Sli successfully. Nvidia control panel acknowledges the two cards as quad Sli.

However, the problem is that Windows 7 64-bit Ultimate is showing me the graph memory size as 4 GB while it is supposed to be 8 GB because of the Sli. Also the benchmark from all software is giving me a very low score compared to some other guy's benchmark on YouTube.

It gives me a big headache. Does anyone know why this is happening? If so, how can I get Windows 7 to recognize all 8 GB of memory?

Thanks for your help in advance.

My computer specifications:

(Processor: Intel Core i7-3930k @3.2GHz(12CPUs))---

(Memory: 65536 MB Ram 1866 MHz)--

(OS: Windows 7 Ultimate 64-bit)--

(OCZ 240GB as SSD PCIe drive for booting and storage disk)--

(DirextX version: DirectX 11)--

(VGA Card: 2 X EVGA GTX 690 Dual GPU. Each GPU is 2 GB, so total memory should be 8 GB.)--

(MotherBoard: ASUS Rampage IV Extreme)--

Others with lesser specifications get a 2500 score in heaven benchmark while I get 1501 as if it is one card.

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Could you supply the Card maker, driver version of the cards, your motherboard type and manufacture, amount of RAM installed. "Very Low score vs other guys..." may not get answered. But benchmark expectations as posted by manufacture vs your actual results (should they be poor in comparison) my get you more info. – Carl B Aug 11 '12 at 14:21
up vote 1 down vote accepted

Video RAM with SLI does not stack, it is mirrored so your total will still be 4 GB as each card is only using it's own Buffer. How SLI works (by default, there are other modes) is each card renders a frames independently in an alternating order, so card 1 then card 2 then card 1 and so on. This is also what creates the "micro stutter" that you often hear people complaining about.

Here's the VRAM question on NVidia's SLI FAQ.

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