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First of all, I'm no computer expert, so I apologize if my question seems too trivial or somewhat ill-posed.

After googling a bit, I've found that the GeForce GTX 675M Discrete Graphics (DDR5 4G VRAM) is a better video card than the Radeon HD 6970M (2GB GDDR5). This seems pretty obvious.

However, all references I've looked compare them without taking into account this specific amount of memory (4G for GeForce, 2G for Radeon). They just compare "GTX 675M" and "Radeon 6970M". I don't know if it's a common assumption to use 1G for both or what (couldn't find it either).

My question is: How big is the difference between those cards, taking into account the memory? I'm specially interested in the FPS Rate for demanding games, so you could use that as a measure.

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up vote 2 down vote accepted

Frame rates are dependant on the graphical chip's architecture, the speed it is run at and the bandwidth to the (on board) RAM. Once you have enough adding more more will not make a card faster.

So a 4GB VRAM GTX 675 is as fast as a GTX 675 with 2GB VRAM, or with 1GB VRAM.

The only reason to get a card with a lot of VRAM is:

  • Future proofing it (newest games always seem to use more)
  • Using a large number of monitors (2GB seems to be recommended of you use 6 monitors)

So as a answer: No they do not take the memory into account because there is no need to take that into account.

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thank you. What about increasing resolution (say from 1024x768 to 1920x1200)? Does it also require more VRAM? I ask because it seems to be more or less the same as using more monitors. – student Jul 29 '12 at 23:39
Increasing the resolution means more pixels to calculate. It means your chips will need to do more work and it needs more bandwidth to access the data worked on. It also might use slightly (in the order or megabytes, not gigabytes) more memory to hold and buffer the results. But you can play (almost?) any modern game on high settings and with 1920x1200 resolution on a 1GB VRAM card. Not that more will slow it down, but more will not make it faster either, more will cost more, and more will use more power. – Hennes Jul 29 '12 at 23:45
Although this answer is correct, it is also worth pointing out that it is quite common for cards with higher amounts of VRAM to have LOWER clock speeds than their equivalents with less VRAM, so they do not always necessarily perform any better - it depends on the circumstances. Also, there are quite a few games available now that you cannot play at 1920x1200 with 1gb of VRAM. – Oliver G Jul 30 '12 at 1:00
Aye. I have seen that happen a lot with dual GPU cards. Lowering the clock speed lowered the performance of these monster cards, but also allowed them to stay with the power envelope of PCIe (max 300 Watt total, of which max 75 via the PCIe slot). ---- However this is due to the model of the card and not due the the VRAM. – Hennes Jul 30 '12 at 1:35
In any case, is it safe to assume that the Radeon 6970 with 2gb can run almost any game (as of now) with maxed graphics? And what about the GTX 675M? – student Jul 30 '12 at 4:12

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