Hi all,I've been tweaking for a while trying to get the best BP and or Reject Threshold in FSX and whilst I dont fully understand whats going on there I think I have found my sweet spot.However some posts around here are saying nowadays our CPUs are driving to much data at the GPUs. This is perhaps the case with me. I have a 4.9 2600k with a 590GPU running 3X 30'' screens.I know FSX dosnt do SLI like other games but if I slid another 590 in under SLI will the data overdose from the 4.9SB spread the workload over the two GPUs?thxIM2

For a long time I ran a single and then 2 crossfired ATI5870s with FSX, and in my tests I did not notice any improvement in FSX from having the second GPU.Based on similar posts for SLI when I researched it here at the time I think SLI will be the same, I think the only FSX improvement from SLI seems to be if you need the SLI for 3 monitor surround mode.

With a modern GPU FSX is usually botlenecked at the CPU. But add enough screens with advanced AA and your bottleneck could become the GPU.So if the bottleneck is the CPU, a second card in SLI won't be of any help (and could even increase microstutters). But if you have lots of large screens, well then you might getter better performance with a sceond card in SLI.Cheers,- jahman.

The x8 PCIe bus speed your GPUs would get with an SLI setup on your 2600K would effectivly stop you from seeing any benefit. I would say that you get worse performance with SLI on 2600K.

SLI hurt FPS on my last X58 system. Saw a performance jump when I finally got rid of my other GTS450.

Results here suggest that SLI has little effect either way however, there is no other means of running 3x1920x1200 (except Eyefinity?).It will be interesting to see whether Ivy Bridge increases performance on my system or whether the PCIe bus or GTX580's are now limiting it.

Edited February 15, 201214 yr by DescendDescend

The x8 PCIe bus speed your GPUs would get with an SLI setup on your 2600K would effectivly stop you from seeing any benefit. I would say that you get worse performance with SLI on 2600K.

That's a good point, and a reason to upgrade to IB PCIe 3.Cheers,- jahman.

Not to sidetrack the conversations but I'm also hoping Nvidia gets a clue and includes 3 monitor support in the upcoming Kepler/680.ATI has had 3 monitor support on their top and even mid level cards for more than 2.5 years now and it's getting kind of ridiculous that we still need to do SLI just for 3 monitor support on Nvidia.

Edited February 15, 201214 yr by kludger

Not so sidetrack the conversations but I'm also hoping Nvidia gets a clue and includes 3 monitor support in the upcoming Kepler/680..... it's getting kind of ridiculous that we still need to do SLI just for 3 monitor support on Nvidia.

Interestingly, I have not heard even a rumour to this effect. :huh:Kind regards,

Interesting reading thanks guys. I'm not after frame rates as they are very good even with 3 X 30'' screens at 6044 X 1080 but without the Reject Threshold tweak I have stutters so one would think my wonderful SB CPU is hammering the GPU.I find it interesting that in jahman's post he says SLI can increase microstutters, if this is the case I'm now wondering if my single 590 which is really just two 580s side by side could be the reason for my stutters. As I understand it the Reject Threshold tweak just throttles back the data from the CPU hence my reduction in stutters, please correct me if I'm wrong here.I'm currently experimenting with Prepar3D and find a slight improvement in stutters but I have also found that the Reject Threshold tweak makes no to little difference in this new plateform. IB PCIe 3 looks like the way to gothanks allIM2

IB PCIe 3 looks like the way to go

+12X the bandwidth of PCIe2. Auto-gen heaven in my opinion. :Big Grin:

without the Reject Threshold tweak I have stutters

When I have researched the effects of the PCIe bus, Reject Threshold and BP=0 offers improvements in FPS and stutters at times when changes in PCIe bandwidth is the only hardware change that have any significant impact. So if BP=0 or Reject Threshold is giving you improvements. Higher PCIe bandwidth will also give you improvements. The opposite is also true. Lower PCIe bandwidth will give you even worse performance.The GTX590 is equiped with a NF200 PCIe bridge chip. So the CPU is feeding 16 lanes to the NF200 that in turn is feeding 16 lanes to each of the two GPUs on the card. So one GTX590 is a lot better then GTX580 in SLI on the 2600K for FSX.

Back in the days when I was running SLI (2x7800GT) I saw that FSX got an improvement when I took one out one day. Now after I discovered the significance of the PCIe bandwidth in FSX I do wonder if it was that SLI also forced me to split up the PCIe lanes on the motherbord that hindered me from getting a performance increase with SLI.

Last week I added a 2n GTX 580 for SLI running and the slots were at 8x each with 2 video cards in my system (P67 chipset). Had to return one GTX 580 because it was defective and now I'm back to 1 GTX 580. Frame rate went down from 51 to 50 fps in a scenario I tested out in FSX before I added the 2nd card and after, using FRAPS and getting the average fps after 1 minute. Single-GPU mode and the default SLI mode set by the drivers gave me the same frame rates, sitting there on the runway, and it looked like SLI was barely utilized because the AFR load bar was empty and barely moved. I was reading in this form in a thread that mentioned that going from PCI-E 8x to PCI-E 16x resulted in an % performance increase with lots of autogen. I never got an % reduction in frame rate going down to PCI-E 8x from PCI-E 16x, I only lost 1 fps. Did the person mean the loading of autogen was faster but not the frame rate when the PCI-E bandwidth was increased? Maybe I didn't have the ideal scenario and settings to make it a difference, I wasn't moving the aircraft while testing and just sitting on the runway?

FSX does not support SLI or Xfire.