680i and the three PCI-E slots

[cruise]

As you are probably aware, most 680i boards have 3 PCI-E x16 slots, two are truly 16x and one is 16x but powered only by 8x architecture. It was originally intended for physiX cards and the like.

I was wondering if anyone knows of some benchmarks testing the performance impact of 8800GTX SLI while using the 8x slot and one of the 16x slots, instead of using both the 16x slots.

Surely it must have being done by someone, but I can't seem to find anything.

Any help appreciated.

[doompc]

Look for a AM2 nForce 570 SLI board review, it's also 16x+8x configuration.

But, on the 570a SLI both PCIe slots are connected to the same bridge.
On the 680i SLI the 1st slot is connected to the northbridge and the 2nd (and the 3rd) one to the southbridge (wich is in fact a 570a SLI), but the connection beetwin the bridges is made by HyperTransport. it's not as crappy sollution as the Intel P965 (16x+4x).

[cruise]

Look for a AM2 nForce 570 SLI board review, it's also 16x+8x configuration.

But, on the 570a SLI both PCIe slots are connected to the same bridge.
On the 680i SLI the 1st slot is connected to the northbridge and the 2nd (and the 3rd) one to the southbridge (wich is in fact a 570a SLI), but the connection beetwin the bridges is made by HyperTransport. it's not as crappy sollution as the Intel P965 (16x+4x).

But the performance of the AM2 board is hard to compare, because any differences in performance might have nothing to do with the 16x/8x configuration but the board itself.

What would be ideal is an SLI benchmark with the two 16x slots, then with the 8x slot on a 680i based mobo.

[sonofander]

I remember reading a review comparing the 680i (16x16) to the 650 (8x8). there was NO difference in performance between the two.

[cruise]

It would be good if we could find that review! It's not that I don't believe you, but I have also read that certain things can affect it, such as high resolutions.

[sonofander]

I believe it was something I saw on Anandtech or Tom's Hardware... gl

[cruise]

hm couldn't find anything on either site specifically about that.

Hopefully someone can provide a link

[Frank M]

Maybe this is what you are looking for?
Compares gfx cards @ x16, x8, x4 and x1.
http://www.tomshardware.com/2007/03/27/pci_express_scaling_analysis/

Summary: in games, the 8800GTS benefited a bit in the x8 -> x16; while the
x1900xtx was about the same, sometimes even at x4. On scientific programs
though, bw mattered.
OTOH, the test was very limited in range.

[cruise]

Maybe this is what you are looking for?
Compares gfx cards @ x16, x8, x4 and x1.
http://www.tomshardware.com/2007/03/27/pci_express_scaling_analysis/

Summary: in games, the 8800GTS benefited a bit in the x8 -> x16; while the
x1900xtx was about the same, sometimes even at x4. On scientific programs
though, bw mattered.
OTOH, the test was very limited in range.

That's definitely helpful, but like you said they don't try out different cards like the 8800GTX and different resolutions.

I'll keep looking though, if anyone does know a more in depth comparison between 8x and 16x PCI-E SLI I would appreciate letting me know. :up: