X58 and SLI heads up - AVS Forum
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post #1 of 12 Old 03-15-2009, 12:10 PM - Thread Starter
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for those that want to squeeze out the max from their x58 and two card SLI setups, heres a heads up. Most x58 mobo that do not use the NF200 chip addon will have their 16x slots run at 16x16x8(4) or 16x8(4)x16 depending on the mobo manfacturer. If you want to keep all the vid cards at 16x, then you can not install anything into the 3rd 16x slot. By installing a card into the 3rd slot, the setup becomes 16x8x8(4) or 16x8(4)x8. Over all perf is not greatly effected but there is a very minor hit going from 16x to 8x for dual card SLI setups. Does not apply to a dual GPU card like the 295 since it only occupies one 16x slot. Not sure about quad since I do not have two 295's for testing but I would guess the same applies since there is only so much bandwith native with the x58 without the NF200.

Dawn on me after I replaced my X-fi Prelude sound card (PCI) with a X-fi Forte (PCI-E) sound card. Went back to the X-fi prelude.

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post #2 of 12 Old 03-15-2009, 01:40 PM
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I think the 295s have the NF200 on the card.
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post #3 of 12 Old 03-15-2009, 01:48 PM - Thread Starter
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Quote:
Originally Posted by steven975 View Post

I think the 295s have the NF200 on the card.

just an internal SLI bridge chip as far as I know. It actually have a SLI cable between the two halves if I rem correctly. Not 100% sure tho.

Randall Morton could prob comment on this since he's taken a 295 apart.

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post #4 of 12 Old 03-15-2009, 03:11 PM
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no, it's a chip that takes the incoming 16 PCI-E lanes and then gives each GPU 16 lanes. Supposedly, it also intercepts GPU-GPU PCI-E communication so it doesn't have to go through the chipset, too. Yes, there's also an additional SLI bridge, too, but it's just a link and not run by a separate chip.

The original 7900GT*2 (whatever its name was, the OEM special with the GPUs on one board, not the 7950GX2) didn't have this chip. It just gave each GPU 8 lanes, but also had to be recognized as 2 PCI-E devices, hence the need for a very special BIOS in order to get it to work).

The original NF100 was a bridge of this type that was on the 7950GX2. I think they updated it to the NF200 for the 9800GX2, and also used it on the 780i . The Skulltrail used 2 NF100 bridge chips. If the 9800GX2 and the GTX 295 do not use the NF200 it is a chip of similar functionality, at least. It may not have a name, but I'd guess even if is not divulged to be the NF200, that's probably what it is.
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post #5 of 12 Old 03-15-2009, 03:30 PM - Thread Starter
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that can explain why the 295 is so expensive. Learn something new....

But still does not matter when you fill all the slots on the mobo, since you are still limited by the PCI-E bandwidth regardless whats on the vid card without the NF200 on the mobo.

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post #6 of 12 Old 03-15-2009, 03:59 PM
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well, something like a GTX295 would get the same bandwidth with or without the NF200 on the motherboard, but for 2-3 GTX's in SLI, the NF200 serves a definite purpose.

In fact, on my MSI 780i board, using SLI on one of the slots not serviced by the NF200 results in performance drops.
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post #7 of 12 Old 03-15-2009, 04:15 PM - Thread Starter
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Quote:
Originally Posted by steven975 View Post

well, something like a GTX295 would get the same bandwidth with or without the NF200 on the motherboard, but for 2-3 GTX's in SLI, the NF200 serves a definite purpose.

In fact, on my MSI 780i board, using SLI on one of the slots not serviced by the NF200 results in performance drops.

Thats weird since on 780i mobos the Nf200 is suppose to be active for all three 16x slots, thats with all the eVGA 780i that I'd used in the past.

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post #8 of 12 Old 03-15-2009, 04:41 PM
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On my 780i board, the NF200 is active for the first 2 x16 slots.

The NF200 is connected to the 780i northbridge (identical to the 680i northbridge, actually). One x16 link to the NF200, and from the NF200 2 2.0 x16 links to the PCI-E slots. The link between the 780i and the NF200 is actually a PCI-E 1.1 x16 link, but clocked at about double the PCI-E 1.1 specification.

The 3rd PCI-E slot is connected to the 570 MCP southbridge (same chip that powers the AMD 5xx Nvida platforms actually). I'm pretty sure that's the way all of the 780i models are. Here's a block diagram of the 780i:

http://www.anandtech.com/cpuchipsets...spx?i=3180&p=2
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post #9 of 12 Old 03-15-2009, 04:47 PM - Thread Starter
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OK I was wrong, but with NF200 on the mobo you still have all three slots at 16x. Maybe thats why when I tested tri SLI, GPU Z reported all the vid cards were working at 16x. That was what confused me since I am a don't RTFM type. Thanks for the clarification.

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post #10 of 12 Old 03-16-2009, 07:40 AM
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Why is it always so complicated with Nvidia?

I'm now in Tri-Crossfire (4870x2 + 4870 1GB), and it took me 5 minutes to set-up everything and play. Put the cards in, boot, and then play.

I can play everything at 2560X1600, with max AA... Something even 2x GTX295 can't do... And with the 4890x2 coming in a month, Nividia will, again, play catch-up for another 6 months...


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post #11 of 12 Old 03-16-2009, 08:14 AM - Thread Starter
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Quote:
Originally Posted by LEVESQUE View Post

Why is it always so complicated with Nvidia?

I'm now in Tri-Crossfire (4870x2 + 4870 1GB), and it took me 5 minutes to set-up everything and play. Put the cards in, boot, and then play.

I can play everything at 2560X1600, with max AA... Something even 2x GTX295 can't do... And with the 4890x2 coming in a month, Nividia will, again, play catch-up for another 6 months...

It not complicated with Nvidia since it just plug and play. The question is what are the 16x peg slots run at with the cards install. ATI cards have the same issue if you use up all the 16x peg slots. Its not a Nvidia probm as such but the amount of bandwidth available native to the PCI-E slots with the x58. The NF200 just adds additional bandwidth for Nvidia vid cards. Just see what GPU Z shows you peg slots are set to when you install cards in all three 16x peg slots. See what happens when you install like a PCI-E sound card in the third slot, bet CPU Z will show you are running at 16x8x8 with the your eVGA x58 SLI mobo. Peg slot 1 and 2 can run at 16 and slot 3 only at 8. Peg slot 1 and 2 can only run at 16 (16x16) if slot 3 is empty otherwise it is 16x8x8. If you install your cards in slot 1 and 3 you will get 16x8 with the eVGA peg slot layout. Other manufactures varies the peg slot locations but they all have the same limitations on bandwidth with out the NF200. Thats my understanding.

Just as I stated in the beginning the performance decrease is min when comparing 16x16 to 16x8, but its there.

At least with SLI you norm do not have to wait a month(s) for game support like with the Xfire game profiles. Worst case with SLI you can alway create your own profiles, Let see if you can do custom game profiles with the ATI cards...back at you...hehehehehe.

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post #12 of 12 Old 03-16-2009, 03:57 PM
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yes, and the Nvidia cards scale better more consistently with multiple GPUs.

ATI cards can scale from 1x to somewhere ahead of Nvidia on a few games, but the norm is less scaling with multiple GPUs than Nvidia. The 4890 is just a clock bump, so don't expect 50% gains or anything. 3 4870s isn't anywhere close to 1.5x faster than 2 of them. Nor is Nvidia, but at least it is better.

OT, but on T for the post...I just pulled the trigger at Newegg on a BFG GTX295. The EVGA was sold out, but the BFG was the same price but included the HDMI cable, too. I'll use my GTX295 for games and one of my 8800GTs for Physx now. I also ordered a Corsair TX850W with +12V rail at 70A.
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