PCI Express 3.0 questions for tech guys

[BIGNEWY]

Hi all

 

need some help understanding PCIE.

 

My current motherboard does not support PCIE 3.0 and I am running a HD7850oc 2gb.

 

But I am considering an upgrade depending on what the hit is like with EDGE.

 

Are the latest GPU's backward compatible, and if so does it really make a difference on performance ?

 

Thinking of either going NVIDIA or ATI R9 290

 

any advice appreciated

[MTFDarkEagle]

Yep, 3.0 is perfectly backwards compatible with 2.0.

 

Does it make a difference? Current DCS engine: no.

EDGE? Who knows.. :P

[Rhinox]

Does it make a difference? Current DCS engine: no.

You did some benchmarking? Because there *is* some difference:

 

v1: 250MB/s (speed per lane)

v2: 500MB/s

v3: ~1GB/s

v4:~2GB/s

 

The question is not if it makes difference, but how much impact does it have...

[karambiatos]

i dont think youll see any difference between a 7850 on a PCIE 2.0 or a PCIE 3.0, or maybe a negligible difference, i could be wrong, but i dont think the 7 series is maxing out the PCIE 2.0 slot.

 

on a side note, make sure your CPU can support PCIE 3.0, otherwise its useless to buy a mobo that supports it when your CPU doesnt.

 

and if you really want a new GPU a 280x is probably the best in the price to performance ratio, if you are looking to save a few of your monies.

[MTFDarkEagle]

You did some benchmarking? Because there *is* some difference:

 

v1: 250MB/s (speed per lane)

v2: 500MB/s

v3: ~1GB/s

v4:~2GB/s

 

The question is not if it makes difference, but how much impact does it have...

 

Does it make a difference in FPS in DCS? Because that's the point. Off course *technically* there is a difference!

And to answer your question, no. I haven't done any benchmarking. But knowing the current DCS engine, v2 -v- v3 performance wise won't make any difference *I guess* (how's that? Better that way? :P)

[Rhinox]

It's like saying "HD vs. SSD does not make difference in DCS". Basically true, except a few cases. As with PCIe 2.0 vs 3.0...

[MTFDarkEagle]

except a few cases.

 

Name one that applies to PCI-e 2 v 3.

 

Don't get me wrong, I'm not trying to be a smart arse, I'd love to be corrected but I don't think it'll make any difference in the current DCS engine.

[SkateZilla]

No Single GPU (Outside of Maybe Titan and Pro Cards), actually use an entire Full PCIe2.0-16x Lane.

Titan and Professional Cards Use more Bandwidth than the 780ti, 780 and Below, But I Doubt they Max out a Single x16 Lane either,

But for the sake of Arguments, Lets say they are Close and Could w/ Double Precision FPU and other Professional GPU Goodies enabled.

 

If you plan to go R9-290/X, they don't fully use the entire 2.0 x16 Bandwidth either, Under Equal Load. They Could Peak and Get close Liek the Titan/780s.

 

There is about 1-5% (A Peak of maybe 7%) FPS Difference Between 2.0 and 3.0

Simply because the individual lanes have more peak bandwidth. Lets just say must benchmarks are within 5 FramesPerSec of each other.

 

PCIe3.0 is not Twice the Bandwidth as PCIe2.0, (5GT/Sec vs 8GT/Sec),

However the Data Encoded more Efficiently, which = 500MB (2.0) vs 985MB (3.0) Per Lane.

 

Infact, a 7970 Can Run games fine, at PCIe2.0-x8, and PCIe3.0x4.

 

So if you have a PCIe 3.0 Chipset and CPU that Supports it,

You can Run Mainstream GPUs in XFire/SLI using 2 Slots (2.0 or 3.0) at 8x Each or 4 Slots at PCIe3.0 x4 and have Minimal Performance Hit.

 

in Fact, when I Ran Dual 7950s, The Performance Difference Between Xfire in PCIe2.0-16x on Both Slots vs PCIe2.0-8x on Both Slots was an average of 5 FPS, going back and forth between gains and losses, But TBH, it's pretty much no difference outside of benchmark Numbers.

Edited November 18, 2013 by SkateZilla

[SkateZilla]

You did some benchmarking? Because there *is* some difference:

 

v1: 250MB/s (speed per lane)

v2: 500MB/s

v3: ~1GB/s

v4:~2GB/s

 

The question is not if it makes difference, but how much impact does it have...

 

There is no Difference for me, DCS right now is CPU Bound.

[pacotito]

From what I've read although I couldn't confirm. AMD tested crossfired 290x on pci2.0x8 without major performance loss. Like I said I couldn't confirm so take this with a grain of salt.

[-Rudel-]

I run SLI'd Titans on my 2.0 setup. Other than an FPS increase, I've noticed no changes from my old SLI'd 580s.

 

Settings are exactly the same.

[BIGNEWY]

Thanks for the replies all, that has put my mind at ease :)