Enabling SLI on my system results in frame rate DROPs of 30 to 50%! 

 

System description:

ASUS Maximus VI Formula, 4790K @ 4.6G, 16G, RAM

ASUS 980X x2 one in x16 PCIE slot, the other in x8 PCIE slot

P3D on dedicated SSD

Two monitors at 1920x1200.  One runs the main sim view, the other has several 2D panels shown.

PMDG 777

FSUIPC, FreeMesh X, REX, REX Softcloud, ORBX Global, both ASN and PATCX on network, FSDT KIAH, GSX

 

Using one 980x (SLI disabled) my frame rate is very stable at 30 fps with all internal and external views.
 
Switching on SLI and using the NCP and NVI default settings results in a drop to 10-20 fps in all views.  Note that the cockpit view is highest at 20fps and the other internal views are in the 10s.  The GPU usage shows GPU1 running ~3% and GPU2 ~20%.  Flying with this is problematic.  CPU utilization is ~40-50%.

 

I have tried other SLI settings but have made no improvements.
 
Running Battlefield 4 both GPUs are 95%, so SLI hardware is working.

 

Latest NV drivers are installed.

 

My P3D settings are as follows:

[JOBSCHEDULER]
AffinityMask=84
[Display]
ChangeTime=4.000000
TransitionTime=4.000000
TEXTURE_FILTERING=8
MSAA=4
SSAA=0
VSYNC=1
FXAA=0
TRIPLE_BUFFER=1
ActiveWindowTitleTextColor=255,255,255
ActiveWindowTitleBackGroundColor=0,28,140,64
NonActiveWindowTitleTextColor=255,255,255
NonActiveWindowTitleBackGroundColor=24,33,87,64
InfoUpperRightTextColor=255,0,0
InfoUpperRightBackGroundColor=0,0,0,0
InfoLowerLeftTextColor=255,255,255
InfoLowerLeftBackGroundColor=255,0,0,128
InfoLowerRightTextColor=255,255,255
InfoLowerRightBackGroundColor=255,0,0,128
InfoBrakesEnable=True
InfoParkingBrakesEnable=True
InfoPauseEnable=True
InfoSlewEnable=True
InfoStallEnable=True
InfoOverspeedEnable=True
InfoWeaponSystemEnable=True
InfoCountermeasureEnable=True
SKINNED_ANIMATIONS=1
TEXTURE_BANDWIDTH_MULT=30
UPPER_FRAMERATE_LIMIT=33
WideViewAspect=True
FullScreenExclusive=False
FullScreenAutoFill=True
FullScreen=True
TextureLMaxLoad=6
[sCENERY]
POP_FREE_AUTOGEN=1
AUTOGEN_BATCH_LOD=2
AUTOGEN_TREE_MAX_DRAW_DISTANCE=9500.000000
AUTOGEN_TREE_MIN_DISTANCE_TO_LOD=2500.000000
IMAGE_COMPLEXITY=4
[Main]
User Objects=Airplane, Helicopter, Submersible, ExternalSim
LabelsSupported=Airplane, Helicopter
Location=0,0,1920,1170,\\.\DISPLAY1
Maximized=1
HideMenuNormal=0
HideMenuFullscreen=1
FIBER_FRAME_TIME_FRACTION=0.01
LocationFullScreen=0,0,1920,1200,\\.\DISPLAY16
[PANELS]
IMAGE_QUALITY=1
SAVE_AND_LOAD_PANEL_STATE=1
PANEL_OPACITY=100
PANEL_MASKING=1
PANEL_STRETCHING=1
UNITS_OF_MEASURE=0
QUICKTIPS=0
[Weather]
WindshieldPrecipitationEffects=1
MinGustTime=10
MaxGustTime=500
MinGustRampSpeed=1
MaxGustRampSpeed=200
MinVarTime=5
MaxVarTime=50
MinVarRampSpeed=10
MaxVarRampSpeed=75
TurbulenceScale=1.000000
WeatherGraphDataInDialog=0
AdjustForMagVarInDialog=1
DynamicWeather=0
DownloadWindsAloft=0
DisableTurbulence=0
CLOUD_DRAW_DISTANCE=6
DETAILED_CLOUDS=1
OPTIMIZE_DENSE_CLOUDS=0
CLOUD_COVERAGE_DENSITY=6
THERMAL_VISUALS=0
VolumetricFog=1
[CONTROLS]
Controls_Default=Standard
Controls_Current=Standard
KBDAIL=64
KBDELEV=64
KBDRUD=64
[TextInfo.1]
Latitude=1,1
Longitude=1,2
Altitude=1,3
Heading=1,4
AirSpeed=1,5
WindDirectionAndSpeed=1,6
[TextInfo.2]
FrameRate=1,1
LockedFrameRate=1,2
GForce=1,3
FuelPercentage=1,4
[TextInfo.3]
Latitude=1,1
Longitude=1,2
Altitude=1,3
Heading=1,4
AirSpeed=1,5
WindDirectionAndSpeed=1,6
FrameRate=2,1
LockedFrameRate=2,2
GForce=2,3
FuelPercentage=2,4
[slewTextInfo.1]
Latitude=1,1
Longitude=1,2
Altitude=1,3
Heading=1,4
AirSpeed=1,5
[slewTextInfo.2]
FrameRate=1,1
LockedFrameRate=1,2
[slewTextInfo.3]
Latitude=1,1
Longitude=1,2
Altitude=1,3
Heading=1,4
AirSpeed=1,5
FrameRate=2,1
LockedFrameRate=2,2
[DynamicHeadMovement]
LonAccelOnHeadLon=-0.020000
LonAccelOnHeadPitch=-0.010000
RollAccelOnHeadLat=0.010000
YawAccelOnHeadLat=-0.100000
RollAccelOnHeadRoll=0.100000
MaxHeadAngle=5.000000
MaxHeadOffset=0.300000
HeadMoveTimeConstant=1.000000
[VirtualCopilot]
VirtualCopilotActive=0
[uSERINTERFACE]
SHOW_MISSION_CAPTIONS=0
PAUSE_ON_LOST_FOCUS=1
PROMPT_ON_EXIT=1
SITUATION=D:\Working Docs\Prepar3D v2 Files\F-22 KEFD
SHOW_SCENARIO_WINDOW=0
RestoreTimeOnMove=0
Map_Orientation=2
MUTE_ON_LOST_FOCUS=1
[PointOfInterestSystem]
CycleSetting=0
[sOUND]
PrimaryPlaybackDevice={DEF00000-9C6D-47ED-AAF1-4DDA8F2B5C03}
VoicePlaybackDevice={DEF00002-9C6D-47ED-AAF1-4DDA8F2B5C03}
VoiceCaptureDevice={DEF00003-9C6D-47ED-AAF1-4DDA8F2B5C03}
SOUND=1
SOUND_QUALITY=2
SOUND_LOD=0
SOUND_FADER1=0.700000
SOUND_FADER2=0.450000
SOUND_FADER3=0.300000
SOUND_FADER4=-0.790000
[GRAPHICS]
SHADER_CACHE_VERSION=1
MIPMAP_VC_PANELS=1
TESSELLATION=1
TEXTURE_MAX_LOAD=4096
NUM_LIGHTS=4
COCKPIT_HIGH_LOD=1
AIRCRAFT_REFLECTIONS=1
LANDING_LIGHTS=1
DAWN_DUSK_SMOOTHING=1
LENSFLARE=0
HDR=1
BLOOM_LEVEL=2
SHADOW_QUALITY=2
TERRAIN_SHADOW_CAST_DISTANCE=0
CLOUD_SHADOW_CAST_DISTANCE=6
OBJECT_SHADOW_CAST_DISTANCE=2
CONTENT_NO_SHADOW=0
INTERIOR_SHADOWS_CAST=1
EXTERIOR_SHADOWS_CAST=1
SIMOBJECT_SHADOWS_CAST=0
TERRAIN_SHADOWS_CAST=0
VEGETATION_SHADOWS_CAST=0
BUILDING_SHADOWS_CAST=0
CLOUD_SHADOWS_CAST=1
INTERIOR_SHADOWS_RECEIVE=1
EXTERIOR_SHADOWS_RECEIVE=1
SIMOBJECT_SHADOWS_RECEIVE=0
TERRAIN_SHADOWS_RECEIVE=1
VEGETATION_SHADOWS_RECEIVE=0
BUILDING_SHADOWS_RECEIVE=0
SHADOW_NUM_CASCADES_LOW=4
SHADOW_NUM_CASCADES_MID=5
SHADOW_NUM_CASCADES_HIGH=7
SHADOW_NUM_CASCADES_ULTRA=12
GROUND_SHADOW_TEXTURE_SIZE=2048
CLOUD_SHADOW_TEXTURE_SIZE=512
SHADOW_LOG_PARTITION_LOW=0.850000
SHADOW_LOG_PARTITION_MID=0.850000
SHADOW_LOG_PARTITION_HIGH=0.850000
SHADOW_LOG_PARTITION_ULTRA=0.850000
EFFECTS_QUALITY=2
EFFECTS_DISTANCE=2
TEXTURE_QUALITY=3
IMAGE_QUALITY=0
See_Self=1
Text_Scroll=1
[DISPLAY.Device.NVIDIA GeForce GTX 780 Ti .0.0]
Mode=1920x1200x32
[DISPLAY.Device.NVIDIA GeForce GTX 780 Ti .0.1]
Mode=1920x1200x32
[TERRAIN]
LOD_RADIUS=4.500000
TESSELLATION_FACTOR=85
MESH_RESOLUTION=23
TEXTURE_RESOLUTION=28
AUTOGEN_VEGETATION_DENSITY=3
AUTOGEN_BUILDING_DENSITY=2
DETAIL_TEXTURE=1
WATER_REFLECT_CLOUDS=1
WATER_REFLECT_USERAIRCRAFT=1
WATER_REFLECT_SIMOBJECTS=0
WATER_REFLECT_TERRAIN=0
WATER_REFLECT_AUTOGEN_VEGETATION=0
WATER_REFLECT_AUTOGEN_BUILDINGS=0
WATER_REFRACT_CLOUDS=0
WATER_REFRACT_USERAIRCRAFT=0
WATER_REFRACT_SIMOBJECTS=0
WATER_REFRACT_TERRAIN=0
WATER_REFRACT_AUTOGEN_VEGETATION=0
WATER_REFRACT_AUTOGEN_BUILDINGS=0
ENABLE_BATHYMETRY=0
WATER_CLARITY=30
WATER_DETAIL=2
UseGlobalTerrainView=False
[ATC]
AutoOpenAirTrafficWindow=0
UsePilotVoice=1
PilotVoice=0
[iNTERNATIONAL]
ASLAT=2
ASLON=1
MEASURE=0
[REALISM]
PFactor=1.000000
Torque=1.000000
GyroEffect=1.000000
CrashTolerance=1.000000
General=1.000000
UnlimitedFuel=False
AllowEngineDamage=True
TrueAirspeed=False
AutoCoord=False
RealMixture=True
StressDamage=True
GEffect=True
ManualLights=True
GyroDrift=False
CrashWithDyn=True
CrashDetection=False
OnCrashAction=0
AutoTrim=False
[ATTACHMENTS]
WeaponHighlight=False
HighlightDuration=1.000000
AutoWeaponSwitching=False
UnlimitedWeapons=False
UnlimitedCountermeasures=False
IgnoreAttachmentWeight=True
IgnoreAttachmentForces=True
[RECORDER]
RecordAITraffic=True
RecordAirportVehicles=True
RecordLeisureBoats=True
[sIM]
SYSCLOCK=1
OPTIMIZE_PARTS=1
[sTARTUP]
DEMO=0
STARTUP_DEMO=
LOAD_SIMDIRECTOR=1
LoadWindow=1
[FACILITIES]
COUNTRY=
STATE=
CITY=
GTL_BUTTON=4096
[Misc]
Com_Rate=7
[TrafficManager]
AirlineDensity=40
GADensity=10
FreewayDensity=10
ShipsAndFerriesDensity=10
LeisureBoatsDensity=10
IFROnly=0
AIRPORT_SCENERY_DENSITY=1
[AContain]
ShowLabels=0
ShowUserLabel=0
ShowLabelManufacturer=1
ShowLabelModel=1
ShowLabelTailNumber=1
ShowLabelDistance=1
ShowLabelAltitude=1
ShowLabelAirline=0
ShowLabelAirlineAndFlightNumber=0
ShowLabelFlightPlan=0
ShowLabelContainerId=0
ShowLabelAirspeed=0
ShowLabelHeading=0
LabelDelay=1000
LabelColor=FFFF0000
[DISPLAY.Device.NVIDIA GeForce GTX 980.0.0]
Mode=1920x1200x32
[DISPLAY.Device.NVIDIA GeForce GTX 980.0.1]
Mode=1920x1200x32
[FlightPlanMap]
LineWidth=2
[MULTIPLAYER]
condAccoutPassword=0
VoiceVolume=-1.580000

Did you clean install P3D and Drivers?  (or at least drivers first)

 

I'm having the opposite experience - gaining about 30%

Also delete shaders.

 

Vic

New drivers installed/reinstalled.

 

P3D reinstalled several times (initial due to CTD on P3D startup).

 

Shaders deleted.

Further testing shows that the drop in fps occurs when a panel view is put on the second monitor.  This may be a "feature" of SLI.  Both monitors are connected to GPU1 and have the desktop extended across them.  I desire to have the sim on one monitor and specific displays (DCUs and EFIS) on the other monitor.  Any suggestions?

I notice that you have four display device lines in your cfg:

 

[DISPLAY.Device.NVIDIA GeForce GTX 780 Ti .0.0]
Mode=1920x1200x32
[DISPLAY.Device.NVIDIA GeForce GTX 780 Ti .0.1]
Mode=1920x1200x32

 

[DISPLAY.Device.NVIDIA GeForce GTX 980.0.0]

Mode=1920x1200x32
[DISPLAY.Device.NVIDIA GeForce GTX 980.0.1]
Mode=1920x1200x32

 

I don't know if it has any effect on SLI, but you should probably delete the 780ti lines.

Thanks for pointing that out.  I've removed them, and there is no improvement.  Sigh...

  I have a few of questions; why do you have vsync enabled, when your fps are locked at 33? It is my understanding, Vsync will only function at frame rates above 60.

 

   Why the affinity mask setting of 84? Again, my understanding is that the affinity mask is best left for P3D to handle.

 

   Do you have hyper-threading disabled for some reason? P3D is multi-core aware, so why not give it all the help it needs. 

 

  Maybe try running without the FFTF, and affinity mask, being set in the cfg file. I am no expert, but, maybe running SLI may require a different set of parameters for your system.

 

  Cheers, Craig

 

 One more note, running your 980's with one @ x16, and the other @ x8, may in fact be limiting both cards to x8 speeds. Actually creating a bottleneck between the OC'd CPU and the twin GPU's. Definately check with your mobo manufacturer, as to which slots to use for best performance.

Edited May 25, 201511 yr by Jazzfan

I think Jazzfan might be right about the slot arrangement. Don't you have a PCIEX16_1 and PCIEX16_2 slots?

No, the MB is old enough that it one slot is x16 an one is x8 and with two cards, you get x8.  I'm thinking that this is the problem.  It would explain why it run better without SLI.

 

I had tried several AMs (including none) and it had little/no impact.

 

Good point about vsync.