6-way CrossfireX?

[Bolas]

I'm interested in building a monster system with three 30-inch monitors, each one powered by it's own Hemlock card in Eyefinity. That should give amazing frame rates on all games even with enthusiast detail settings, I would think.

On previous generations of NVidia graphics cards, 3-way SLI was possible, 4-way SLI was possible with a pair of dual GPU cards or with a specialized motherboard, but 6-way SLI was not possible, presumably due to no drivers for it.

On previous generations of ATI graphics cards, I didn't see the 3-way versions, only 2-way (or 4-way using dual GPU cards).

Maingear Shift and Alienware ALX can apparently handle a 3-way CrossfireX setup with triple 5870's -- but not currently with Eyefinity, only for one monitor. Presumably improved drivers will fix that at some point. I don't see other vendors (Cyberpower, IBuyPower) offering the 3-way CrossfireX, so perhaps that's not something that is easy to do.

With Hemlock coming out this month, using a pair of those cards should get you to 4-way CrossfireX, assuming that you get drivers that can handle that setup. But 4 GPU's doesn't work so good for running an odd number of monitors (presumably) something that is practially essential for games with crosshairs in the middle of the screen.

Another thought is that the action in the middle of the screen on several games (HAWX, Batman) is more intense than the action on the peripheral, so it might be possible with a pair of 5970's to have one card running the center screen and the other card running the two outside screens and still have roughly equal work loads and good synchronized frame rates. I wonder if this will be the case? That might be how ATI works around the issues with GPU/monitor mis-match.

Does anyone know if it will be possible at some point in the future to run triple ATI cards, preferably 5970's, in 3-way (or 6-way) CrossfireX? I would sure love to find a motherboard, case, and drivers that could handle triple 5970's. That way I don't even have to mess with DisplayPort to DVI adapters in order to run triple Dell 3007WFP's, I just plug one into each monitor and I'm done.

 

[Bolas]

I wonder if it is software, firmware, or hardware that is preventing 6-way SLI? If I put three Nvidia 295's into a motherboard, why can't I get them to all work together to run one monitor? Any idea, Anand?

 

[SlowSpyder]

You can run 2, 3, or 4 GPU's in CrossFire. So you'll likely be able to use 3 GPU's if you want by running 3x5870's or a 5970 and a 5870... but the rumored specs of the 5970 say it'll be two 725MHz cores, so unless you overclock it 3x5870 is likely to be faster.

Unless AMD hasn't disclosed something about their upcoming 5970, you cannot run 6 GPU's in CrossFire. I believe there are only provisions on the 4870x2 to connect 2 of them in CrossFire, I assume the 5970 will be the same. The GTX295 is the same type of deal. So running more physically cannot be done.

I'm not 100% famililar with Eyefinity as it's not something I'm likely to make use of, but I'm not sure that you assign one GPU to each monitor if you use 3 GPU's and 3 monitors. I think it would just see the 3 x 30" resolution as a single 7680 x 1600 resolution and use the three GPU's in CrossFire. But I'm not 100% sure, I'm sure someone can correct me if I'm wrong. If it did actually assigne one GPU to each monitor it'd be difficutl to use different number of GPU's and monitors, and as far as I'm aware that's not a problem, so I don't believe it uses a GPU per monitor set up. Again, someone can correct me if I'm wrong. But I believe you think it works differently than believe it does.

 

[Gutcheck2009]

It's an interesting idea, but how would you power it? I think you can not do 6 GPU's as SlowSpyder says. What I am going to try however is one 5970 and 2 5850's.

 

[Bolas]

It's an interesting idea, but how would you power it? I think you can not do 6 GPU's as SlowSpyder says. What I am going to try however is one 5970 and 2 5850's.

I would power it with a twin power supply system. Cyberpower used to have a Gamer Extreme XI unit that came in a huge case and had dual power supplies. Looks like they've discontinued that, presumably because not enough people could afford it's $4k+ price tag.

The number of physical connectors on the cards would be the potential problem, as SlowSpyder points out. For a 3-way SLI system, you need a pair of connectors at the top of each card -- so that you can connect the middle card to each of the other two cards. If there is only a single connector on the top of the card, you are then for sure stuck connecting it to only one other card, capping things at 4-way for twin core cards.

Perhaps someone will do a non-reference design that is capable of more than 4-way crossfireX, similar to what EVGA did with their classified 4-way SLI to make it so that more than three GTX285's could be used in the same system? Perhaps a non-reference 5970 card would have two crossfire connectors on top, and then all you would need would be firmware, drivers, and cabling to make it work. Now that would be quite the setup, but doesn't seem like it is currently possible.

Here's another thought for CrossfireX greater than 4-way, one that would potentially work both from a physical and logistics standpoint.

Have a 3-slot motherboard with a 5970 in the top slot, a 5870 in the middle slot, and a 5970 in the bottom slot. Each of the 5970's has only one connector on the top of the board, but the 5870 has two connectors -- one for each of the 5970's to connect to for CrossfireX. Then you could use that to run five 30" monitors in portrait mode, with a single gpu for each monitor, and all three cards linked together despite the limitation on only one CrossfireX connector on the top of the 5970 cards.

I guess at that point, I'm probably just better off running three 5970 cards and sticking to three monitors, though. Less hassles.

 

[SlowSpyder]

The 5970's will have one connector, the 5870 will have two. But the connectors will not line up in a way that'll make it possible... when you connect one 5970 to the 5870, that'll be on one plane. The second 5970 would have to connect it's bridge to that same connector on the 5870, you won't be able to get the connector to the other connector. It's just not possible to run more than 4 GPU's. Even if you could, the return would likely be so very minor, or even slow down the system compared to 4 or less GPU's. There's a lot of overhead in running CrossFire or SLi, you get less returns the more GPU's you add. There really just isn't any way to run more than 4 GPU's in CrossFire.

Again, you don't need 5 GPU's to run 5 monitors as I stated in my prior post. To the best of my knowlege, Eyefinity will just connect through one GPU and the other GPU's (if there are any) are just used for extra horsepower via CrossFire. You are not running each GPU to each monitor. I'm pretty sure if you did infact run each GPU to each monitor without using CrossFire than you cannot use Eyefinity. If I'm wrong, hopefully someone will correct me. But what I do know for a fact is that you do not need equal numbers of GPU's as monitors.

On the car forums I'm part of, we have a lot of guys who join with dreams of building an 800 horsepower 9 second monster, but really aren't too familiar with the basics of the technology they're planning on using. I have no idea how much knowledge you do have or don't have, but it sounds like you'd benefit from reading up on the information out there in the overviews of these new technologies... it'd really suck if you spent all this money on an uber high end system and it didn't do the things you expected it to do. If you haven't read the AT review of the 5870, it has a very good overview of some of the features of the 58x0 cards. Eyefinity is a fairly new technology, and SLi/CrossFire have their pitfalls from what many multi-GPU users say here. Adding even more hardware and attempting to make some sort of very custom setup, that is not likely to work in the first place, is only gong to make things that much harder to make work right if at all.

 

[SolMiester]

I think slowspyder is correct, the eyefinity demo had 6 monitors to 1 card!

 

[Bolas]

Yep I think he's correct, too.

Guess I'll do a pair of 5970's in CrossfireX for 4-way and then hook up three 3007WFP's to the primary card after buying a displayport to dvi active converter.