Feasibility for SLI/Crossfire with more than 2 GPUs

[JF_Aidan_Pryde]

How about a quad-GPU system?

You could do this a number of ways:
1. 4 boards each with 1 GPU
2. 2 Boards each with 2 GPUs
3. 1 Board with 4 GPUs (Voodoo Volts come to mind)

Option 1 is pretty unrealistic for mainstream PCs. It's hard to conceive anyone making a motherboard with four 16x PCIe slots.

Option 2 appears to be possible. Using SLI and a ring typology, each GPU would need two SLI interfaces to connect to the adjacent GPU.

What does this mean for AFR? The commonly cited problem is the introduction of one frame of latency for each added GPU. What does that translate into really? As in, does the framerate lag? What actually happens?

For SFR, the screen could be split both horizontally and vertically, yeilding four regions. Or you could just split it horizontally using three lines. Not sure how this would affect performance.

How about Crossfire -- is there a way to make 4 GPUs work together?

Please post your thoughts.

 

[nutball]

Don't SGI ship a system which has up to ~32 R300s? Not a consumer piece of kit of course, but shows that it's technically feasible even with last-generation hardware.

Without thinking too deeply I'd say that 2x2 would be the most sensible way to achieve what you're proposing.

 

[AlexV]

I do think that latency would be an issue with even more added cards, and probably the point of diminishing returns would be rather close.

 

[Pressure]

Adding a extra GPU to a PCB does not overcome that you are still limited by the number of PCI-Express lanes available.

So you will run into the same limitations with all the setups but engeeneringly-speaking, some of them are easier to produce than the rest

 

[JF_Aidan_Pryde]

Can someone elaborate on the effects of input latency for AFR?
What does it mean to have 1 frame of input latency? Do things become slower, does the game become choppy, what exactly happens?

 

[Xmas]

Can someone elaborate on the effects of input latency for AFR?
What does it mean to have 1 frame of input latency? Do things become slower, does the game become choppy, what exactly happens?

If AFR is 100% efficient, and if you compare identical resolutions, AFR actually has a bit less input latency. But that's an unlikely case.

Generally, higher input latency means that movements on screen lag behind a bit, thus less precise control because your brain has to decide on "old" data. But it doesn't change smoothness of animation.

 

[Maintank]

We need faster CPUs or bigger monitor resolutions to utilize such a setup.

 

[overclocked]

Correct me if im wrong but didnt ASUS show a board that are coming out soon with 2 PCI-E lanes @ 32 each?

This would be for workstation purpose mainly but..

 

[JF_Aidan_Pryde]

We need faster CPUs or bigger monitor resolutions to utilize such a setup.

Or those Unreal Engine 3 games!