Confusion with SLI dual-core cards

[marfig]

Is it technically possible to SLI four GTX 590 cards?

I answered somewhere else, it is. But I think my answer may be wrong. I based it on my understanding of SLI and on this fella (http://3dmark.com/3dmv/3199988).

However, Nvidia's website refers to a Quad-SLI setup in a different light. Is Nvidia simply speaking of a particular setup of GTX 590 cards, or is this really the most that can be achieved with SLI; i.e. a Quad-Core configuration?

 

[Tharic-Nar]

To the best of my knowledge, Quad SLI is 4x GPUs in whatever configuration, card count excluded. This would most likely be a technical limitation due to the number of available PCIe lanes. Since the 590 is a dual GPU config, it would count as 2 GPUs and the driver treats them as such, since I think it has an SLI bridge chip on-board (nF200 chip or something, used as a PCIe extender), rather than using the system's PCIe bus.

I think the above details in the 3dmark listing is inaccurate, since it is counting each GPU as a card, which i guess from a driver perspective, is correct.

 

[RainMotorsports]

The one thing that is easy to note is that each card by design and each gpu by design only supports particular setups. You will notice that even if SLi allowed for more than quad gpu that the 590's only have one bridge connector limiting them to 2 total cards.

The FTW edition Dual 460's have NO connector being that 460's only support 2 way SLi and they are already SLi's the upper end cards support 3 way and of course 2 590's allows for 4 way.

I am no expert but I don't think SLi by design limits the possibility of more but the current core and card designs of course do. As even nvidia stated the motherboard's SLi support is also an issue to be addressed.

Is it technically possible to SLI four GTX 590 cards?

The answer is no physically, technically being that it was designed missing extra bridge connectors, board trace and possibly nothing on the chip to support it, the answer would still be no. I think the question should have 590 removed and a theoretical card inserted.

 

[marfig]

Ok, guys. Thanks. That clears it up for me.

 

[Kougar]

I think the only hurdle is the software.. the SLI software isn't designed for greater than four cores in SLI period. Diminishing returns has already well set in with four cores, so there was just never a reason to SLI more of them together and spend the time/expense to Q/A the drivers for it.

It IS physically to put four dual-GPU cards onto a motherboard, but it requires four PCIe Express slots with two-slot spacing between each, or some (even more expensive) elaborate watercooling loops that need less height. No ATX motherboard can realistically do this on air (a few tried, but the GPUs would overheat under load). EVGA makes quite a few boards with Quad SLI in mind, but the only true example I can think of is the SR-2, which is a tad larger than even EATX boards size... that one has plenty of room and the PCIe bandwidth required through N200 bridge chips, although the chipset may still prove to be the final bottlelneck even with PCIe 2.0 bandwidth.

The third bit of info is that SLI isn't used for GPGPU, direct computing, or whatever ya want to call it by. SLI must be disabled before most GPGPU programs are able to utilize ALL the graphics cards present in the system. I believe it has something to do with how SLI links all cards as a single entity with the Windows rendering software, but it's been awhile since I payed much attention to this. SLI isn't used when handling massive GPGPU computing clusters.