Whats the difference in FPS x16 vs x8

Schoieuk · 16 Nov 2010 at 00:37

As the title sais, whats the difference your likely to experience in FPS when using either x8 or x16 PCIE SLOTS

Cheers,

Oli

MeatLoaf · 16 Nov 2010 at 00:38

Probably less than 5% if its a PCI-E 2.0 slot.

Essexraptor · 16 Nov 2010 at 00:50

It's really down to bandwidth.

Here's a link to a in depth explanation a little dated but covers the whole thing in full

http://www.tomshardware.com/reviews/pci-express-scaling-analysis,1572.html

My guess is that your thinking about SLI/XFire on a board with the next available slot being X8?

Liampope · 16 Nov 2010 at 01:54

About 1-2% in benches I've seen. It's 4x that will get a GPU not pulling its weight.

biuro74 · 16 Nov 2010 at 11:41

Essexraptor said:
It's really down to bandwidth.

Here's a link to a in depth explanation a little dated but covers the whole thing in full

http://www.tomshardware.com/reviews/pci-express-scaling-analysis,1572.html

Little dated - quite sure - and it regards to PCIe 1.0, if you recalculated it to PCIe 2.0 standard, it would be x4 vs x8 difference.
Between x8 and x16 @2.0 standard there's no difference in practice, in tests x8 is slowert upto 2-3% in hi-res, in medium is as quick as x16.

For multiGPU x8x8 is enough for playing.

stulid · 16 Nov 2010 at 11:50

some results here,

http://www.hardocp.com/article/2010/08/25/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x4x4/

http://www.hardocp.com/article/2010/08/23/gtx_480_sli_pcie_bandwidth_perf_x16x16_vs_x8x8/

http://www.hardocp.com/article/2010/08/16/sli_cfx_pcie_bandwidth_perf_x16x16_vs_x16x8/

Schoieuk · 16 Nov 2010 at 22:07

nice thanks guys, its just for a friend who has a asus p55dle and the board has 1 x8 slot and 1 x16 slot pcie 2.0 and he was wondering if there are any downsides from him getting 2 5870s. But thankls for the fast response seems he will be fine

Liampope · 16 Nov 2010 at 22:19

Not so sure. If you mean the P7P55D LE, according to Asus' website, it can only run x-fire at 16x/4x, so one GPU would not be pulling its weight

Essexraptor · 17 Nov 2010 at 02:14

From my own experience with 2 x 5870's... you'll find that the secondary GPU will spend a lot of time just ticking over.

That was on my UD5 using 2 x 16

Common misconception that SLI or XFire = 2 x performance... it's just not true

Liampope · 17 Nov 2010 at 09:53

davidansell said:
try to get 2times x16

You do love your cheesy, not particularly helpful one-liners!

Essexraptor said:
From my own experience with 2 x 5870's... you'll find that the secondary GPU will spend a lot of time just ticking over.

That was on my UD5 using 2 x 16

Common misconception that SLI or XFire = 2 x performance... it's just not true

Then you bought a 5970 anyway??

Essexraptor · 17 Nov 2010 at 10:50

It's XFire by default ie 2 x GPU's on 1 PCB, different concept with far better results

not 2 seperate GPU's bodged together with a bridge

Nemeses · 17 Nov 2010 at 12:44

really interesting read that, I would have thought x4 would have had a impact, on there the little it had makes no difference in any game.

Porcelina · 17 Nov 2010 at 18:22

Essexraptor said:
From my own experience with 2 x 5870's... you'll find that the secondary GPU will spend a lot of time just ticking over.

That was on my UD5 using 2 x 16

Common misconception that SLI or XFire = 2 x performance... it's just not true

I have to disagree. Not that it is not two times the performance, but that it is a common misconception. I do not think at all that a lot of people just assume that two graphics cards will give double the performance. There is just no reason to believe that.

Essexraptor · 18 Nov 2010 at 03:02

Porcelina said:
I have to disagree. Not that it is not two times the performance, but that it is a common misconception. I do not think at all that a lot of people just assume that two graphics cards will give double the performance. There is just no reason to believe that.

Perhaps the wrong phrase to use

"common misconception amongst the less well informed" may be a little better.

Hell... it's a mistake that I made 14 - 15 months ago and I'll gladly put my hand up to it.

I'm here to learn and become more knowledgeable about my pastime as well as share what little knowledge I have learnt from my past success's as well as my own mistakes!

All the best