[Freak'n Big Panda]

My system:

MSI K8N Neo4 Platinum (PCB Rev1.0)
Athlon X2 3800+ (200x10=2000mhz)
2GB DDR 400 (4 dimms)
ASUS 7800GTX (reference clocks)
200GB Maxtor HD

And here are the benchmarks:



Standard 3dmark06 Run, small (16%) gain moving from PCIe2x to PCIe16x. Game breakdown follows:



Percent Gain for GT1: 16%,GT2: 15%, HDR1: 15%, HDR2: 33%

~15% drops across all games except HDR2 which shows a relatively large drop of 33%. My guess would be that the 256MB frame buffer was filled making it necessary to move additional data over the slow PCIe2x bus.



You can't run the HDR tests with AA enabled but here are game tests 1 & 2 with 4x AA @ 1280x1024. Notice that with AA enabled the difference between 2x and 16x in GT2 nearly triples to 43%, again the added sampling most likely demanded more than the 256MB available in the local frame buffer on my 7800GTX.



Please note differences of +/-5% should be ignored due to measurement inaccuracy. Taking this into light we see that oblivion gains absolutely nothing going from PCIe2x to PCIe16x. I was running near maximum settings @ 1280x1024.



Benchmarks were run @ 1280x1024 maximum settings. As we can see stalker gains about 50% in the Buildings time demo and 40% in the Outdoors timedemo.

Feel free to comment on the data, I'm not quite sure why I'm not seeing a performance drop in oblivion. It could be that at these settings the game is largely CPU limited. I'll do a bit more benching later tonight, I might throw in 3dmark05 too if I have time. And yes I know this is largely pointless but I was curious haha.

P.S. I've got a question for the 3D buffs on this site: What exactly is moved across the PCIe bus during game play?

[Richard]

This is not pointless. In fact, it was quite helpful to me. I'm also surprised by the relatively low performance impact.

[fellix]

Not surprised by the numbers from Stalker, as this title is taxing quite heavily the video memory. Try again with 512MB board.

[Davros]

why do manufacturers insist their cards are x16 only
for example ati insist the x1900 needs 16 lanes even though it works fine in a 4 lane slot

the 8800 doesnt work in a 4 lane slot but i suspect its because nvidia has told the card not to and not because it cant

[Arnold Beckenbauer]

Originally Posted by Davros

the 8800 doesnt work in a 4 lane slot but i suspect its because nvidia has told the card not to and not because it cant

You mean, 8800 doesn't work with ASRock 4CoreDual-VSTA (its PEG has 4 PCIe lanes)?

PCI Express Scaling Analysis

The problem with some ASRock mainboards could be, that they are cheap. http://www.asrock.com/mb/overview.as...ual-VSTA&s=775 They miss some PEG/PCIe requirements, and it's possible, that 8800GTX doesn't get enough power.

[AlStrong]

It's an interesting investigation. If you're willing, perhaps it would be worth a look to benchmark Oblivion with those high resolution texture packs.

Hm...I was under the impression that the main use of the PCIE bus was in transferring textures and communication with a second GPU (duplicating textures).

[Freak'n Big Panda]

Hm...I was under the impression that the main use of the PCIE bus was in transferring textures and communication with a second GPU (duplicating textures).

Yeah me too. Anyways I just ran some oblivion benchmarks. Here are the results:



I think this makes a little more sense. The bench consisted of an outdoor scene with lots of grass & tress and a little water. As we can see there's a drop in performance with AA but not with HDR, this would make sense given the memory requirements of each.

[Davros]

Originally Posted by Arnold Beckenbauer

You mean, 8800 doesn't work with ASRock 4CoreDual-VSTA (its PEG has 4 PCIe lanes)?

yes

and my board
P4Dual-880
http://www.asrock.com/mb/overview.as...l-880Pro&s=478

[iwod]

Does that mean in theory if i have 1 - 2Gb Video Memory i would get neligble performance gain from PCIe2x to PCIe 16x?

[Freak'n Big Panda]

Yep. According to these benchmarks anyway. It also means I could run SLI on my MSI K8N Neo4 Plat without a big performance hit, which is pretty sweet. I'd just need to mod my chipset to NF4 SLI from NF4 Ultra with the pencil trick then I should be good to go.

[swaaye]

My Gigabyte DS3, like many 965P boards, likes to drop to PCIe 1X on initial POST when overclocked. It needs a reboot to sort itself out. I'll confirm that PCIe 1X is a major bottleneck for an 8800.

[Davros]

Heres a thought if i were to buy a 16 lane board will i regret it one day because the latest cards perform better with (or even require) 32 lanes

i hope pci-e doesnt end up like agp i hate replacing gfx cards on old mboards because i have to go trawling the net to find out what voltage the agp slot uses and if the card i have is compatable with it

[Pete]

Great post, Panda. FYI, THG investigated the same thing, only with an 8800 and X1900 at x1, x4, x8, and x16: PCI Express Scaling Analysis.

[neliz]

Originally Posted by Davros

Heres a thought if i were to buy a 16 lane board will i regret it one day because the latest cards perform better with (or even require) 32 lanes

i hope pci-e doesnt end up like agp i hate replacing gfx cards on old mboards because i have to go trawling the net to find out what voltage the agp slot uses and if the card i have is compatable with it

As soon as you buy a proper 16x board, they will release PCI Express 2.0 and tell you that PCI Express 1.0/1.1 is totally dead.

[Freak'n Big Panda]

Great post, Panda. FYI, THG investigated the same thing, only with an 8800 and X1900 at x1, x4, x8, and x16: PCI Express Scaling Analysis.

Yay I get +30 nerd points! XD And yeah I saw that THG article shortly after I posted my thread. lol. Originally though I wanted to see if I would take a performance hit for moving my card over to the 2x slot because in the 16x slot it completely covers my chipset HSF resulting in less than optimal temperatures, so it still served that purpose. And of course it's pretty interesting hehe.

[SugarCoat]

Originally Posted by Davros

Heres a thought if i were to buy a 16 lane board will i regret it one day because the latest cards perform better with (or even require) 32 lanes

i hope pci-e doesnt end up like agp i hate replacing gfx cards on old mboards because i have to go trawling the net to find out what voltage the agp slot uses and if the card i have is compatable with it

The cards will be forward compatable as far as i know. I've already read quite a few times that all PCIE 1.0 and 1.1 cards will work in 2.0slots without an issue.

[Dave Baumann]

Yes, physically they are the same, however there can be up to twice the bandwidth per pin. PCIe 1 -> 2 will be similar to, say, AGP2x -> 4x.