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October 26, 2011 5:46:10 AM

So apparently in crossfire or SLI if you have 2 1gb cards you will still only have 1gb of graphics Ram.

How can this be. Does one card not use its graphics ram or do both cards scale down to 50%.



I have read that both 1gb Ram is being used but I can't understand how you could have both gigs being used but only a 1 gig potential it doesn't make sense.

Its like saying I put another 2 gig Ram stick in my mobo to get 4 gb but its only still 2gb but both are being used. How does that make sense. If both are being used then both are obviously available thus you have double.



Crossfire renders frames to card by card so not 1 card is doing all the work. Thus each card has its own ram so. Oh I just answered my own question. I figured it out so each card does one frame then the other does the next and so on.

Wait how does a game run Faster like this if its just a single card taking turn by turn and not them working together. It should be the same speed as one card since only one card is rendering the frame at 1 time.

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October 26, 2011 5:56:48 AM

because both cards need to work with one set of textures of the game, One card can't render say a texture on a box if it don't have it available in its ram because the other has it. Hence both cards have to have the same stuff sent to it.
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October 26, 2011 6:01:55 AM

dormantreign said:
because both cards need to work with one set of textures of the game, One card can't render say a texture on a box if it don't have it available in its ram because the other has it. Hence both cards have to have the same stuff sent to it.



Why couldn't one card load some textures and the other card does the rest.


I know since one card itself has to do a complete frame render then it needs exactly what the other card has on its memory so its mirrored.

But since the cards take turns in rendering frames how does it become faster because one card can only render one frame so fast while the other is waiting for its turn.
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October 26, 2011 6:16:46 AM

It is faster because the processing horsepower is improved. Rather than having one card crunch the numbers frame after frame, you have 2 cards going back and forth. This means it gives each card more time to do the complex calculations while the other card is handling it's current frame. It won't be double the speed because there is overlap, but it is still a pretty large improvement.

Usually, the graphics memory isn't as much of an issue unless you're running SLI with very low memory cards. This all really depends on the number of monitors and resolutions you're working with.
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October 26, 2011 6:24:00 AM

Caruda said:
It is faster because the processing horsepower is improved. Rather than having one card crunch the numbers frame after frame, you have 2 cards going back and forth. This means it gives each card more time to do the complex calculations while the other card is handling it's current frame. It won't be double the speed because there is overlap, but it is still a pretty large improvement.

Usually, the graphics memory isn't as much of an issue unless you're running SLI with very low memory cards. This all really depends on the number of monitors and resolutions you're working with.



How? They take turn so its like one Man counting to 10 VS 10 Men each counting up one after the other. = the same.


How can one card be pre rendering a frame for you when a game is dynamic. It all has to be real time.


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October 26, 2011 6:38:27 AM

well you can't look at it like one man vs 2. computers don't work like that, while one is putting one frame on the screen the other one has the next frame ready and set. so it doesn't increase the horsepower. it increases the efficiency, simply meaning each card has a smaller load Qued up for it
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October 26, 2011 6:47:05 AM

This also depends on if the card is using Alternate Frame Rendering or Split Frame Rendering as well. What you've been describing is AFR. Depending on the game or how you want to set it up, SFR is also used which essentially allows each card to render half of the frame. Once again, the speed is improved due to each card essentially doing roughly half the work.
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October 26, 2011 6:57:45 AM

yeah i remember seeing sfr when sli was first shown, but do you have any idea if one is better then the other. i'd think aff be more efficient since each card has a specific task without having to deal with the other card or having to combine the image
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October 26, 2011 7:08:58 AM

Depends on what you're doing. SFR is usually better for gaming and is often used as the default profile for many games. AFR is regularly used a lot more in Quadro style cards when working with Graphics and Animation.

AFR often times creates better framerates overall, but due to overall increased latency because of the way it actually works, it's not often very good for faster paced action games.
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October 28, 2011 5:29:49 AM

Caruda said:
This also depends on if the card is using Alternate Frame Rendering or Split Frame Rendering as well. What you've been describing is AFR. Depending on the game or how you want to set it up, SFR is also used which essentially allows each card to render half of the frame. Once again, the speed is improved due to each card essentially doing roughly half the work.




SFR makes complete sense as far as frame speed ups.
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