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How does VRAM Stack?

Tags:
  • GPUs
  • Graphics Cards
  • SLI
  • Dual
  • Graphics
Last response: in Graphics & Displays
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October 9, 2013 5:41:38 PM

I know VRAM doesnt stack when you SLI/CF two cards or more. But how come it stacks in the card if its dual GPU?

More about : vram stack

a c 429 U Graphics card
October 9, 2013 5:44:51 PM

Using the 7990 as an example: The actual GPU on the card is what acts, most cards have only one per card. The 7990 has two however and since they are on the same PCB they can add memory as they are technically the same card.
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a b U Graphics card
October 9, 2013 5:47:52 PM

On a dual-GPU card, each GPU basically gets half the available memory on the card.

Casey
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a c 122 U Graphics card
October 9, 2013 5:57:56 PM

Corkeye said:
I know VRAM doesnt stack when you SLI/CF two cards or more. But how come it stacks in the card if its dual GPU?


VRAM does stack and is individually addressable within the x86 memory space, but each GPU is responsible for rendering alternating frames. Alternating frames are usually very similar to each other and thus require very similar sets of data. Each GPU has far more bandwidth to its own memory than it does to the memory on the other GPU (which requires it to snoop through the CPU's memory controller) , so most of the scene elements end up getting duplicated as it cannot be shared in an effective fashion.

Electronics marketing departments love larger numbers, so slapping "6GB DDR5" on a box looks a lot better than "3GBx2 DDR5". They're pandering to simpletons that have money.
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