[Wally]

Without altering my other settings (most around medium) my 2x670's work better with HDR on rather than off.

That is mighty surprising, mate.  HDR does require extra from the cards...

I've tried to set everything to max, no HDR, no blur - again, as I can't stand it, hehe - but I've left the reflection stuff on the default.
This gives me about 45-55fps (looking at the system gadget top value - hope that's the fps)
with HDR on, otherwise all the same it drops to 35-40

I reckon SLI optimisations aren't on....

I read somewhere that either fullscreen on or off in the game settings either makes SLI work or not. You'll have to try with and without fullscreen and see if it makes a difference.

[Bird]

I'm pretty sure it'd be fullscreen on where it should work, because otherwise the desktop takes over...but I'll test it.
Edit: tested. barely a difference.

Then this:
I've reduced the resolution to 4800x1200 (5.7mp) leaving everything the same.   60fps.  That's against the 80-90 of the single 780 at 6.3mp!   In the meantime I was logging via msi afterburner, and the cpu usage was pretty much at max on both cards, memory at ~1850 out of the 2048 (MB).  I've tried both full screen and windowed, barely a difference as I said (windowed was down 5fps or so)...

There is something fishy here I reckon...

Can you post your full pc specs? mine are:
ASUS p8z77-V Deluxe
Intel i5-3570k
Corsair Vengeance 2x8GB

2x GXT670 (Gigabyte)
Sound Blaster recon3D

SilverStone Fortress FT02B-W
Antec 850W Signature

[Wally]

Some specs I remember:

I5-750
4GB RAM
Gigabyte GA-P55a mobo
The Asus 780 is stock overclocked, I think.

[Wally]

And I have FSAA on max, which turns off AA, and also only tried with cube map etc about half way. Haven't tried maxxing out the reflection stuff yet. That could be an FPS killer.

[Bird]

hm...ok so you run fsaa instead of AA - that might be something worth looking at.
Funny thing is that I've read around that the 750 is barely enough to drive a 670 to its full capacity. If that is true, you're definitely bottlenecking the 780 - and still getting much better performance...damn!

Edit: running fxaa (as it's called in the nvidia panel - this is the fsaa I reckon) I get 70-80 fps in 4800x1200.  And around 60-70 in 5760x1200.


I really wish you were living closer, I'd definitely like to give it a try chucking that card into my computer...

[Bird]

Wally, any chance you can run a test with these exact settings?
If you don't mind I'd really like to get to the bottom of this.

(fxaa is ON in the nvidia control panel this time)

These settings give me a solid 60-65 fps in 5760x1200
(the reflections seem to be a fairly big hog of performance when upped!)

[attachment deleted by Wally - running out of space]

[Wally]

With those settings, I'm getting 95 - 115.

I know my CPU is a bottleneck, but I didn't want to fork out for a new mobo and CPU as well. I can get an i7-8xx that will work on my mobo though.

[Dave O]

Hi Istvan, tried you're exact settings on my machine....

Intel i5-3570k
Z77 Extreme 4 MoBo
Corsair Vengence  4x4 GB
Gigabyte GTX 670 1x
Antec 520 high current gamer PSU

3x Asus 23" monitors @ 5760x1080

2 laps at Mugello gave me..  Lowest FPS 50. Highest FPS 60.
most of the lap average was about 55 FPS.

Hope this info helps in some way    Cheers Dave O.

[Bird]

It does, Dave, thanks.  Altho you were running at mugello, that may skew the results a bit, it's still very comparable.  It seems I'm almost getting a single-GPU performance, even though both are being used (watched it in MSI afterburner)
I think it's time to post on the official forums to see if they can help me get it right...


Thank you Wally, yeah it seems we've an SLI optimisation issue here or somesuch.

ps; the bottleneck; not sure if it would come out in AC as of now.  Maybe some other games are more demanding...I think you've got plenty of fps for now

[Bacchulum]

Here's my test Lotus 49 @ Monza66:

System specs:
CPU: Intel i7 930@2.80GHz
GPU: GeForceGTX670 x 2
Mem: 6GB
Res: 5850x1080, 60Hz (3x24" LG Monitors)
Op. Sys.: Win7Pro 64bit

45-50 fps using Bird's settings (dropped to a low of 42 but only at the 'tickle-me' Lesmos)
I guess my MoBo sucks, I'll try and find out what it is.

[Bird]

Mate, you seem to suffer from the same problem.  You've the performance of a single 670 - see Dave's results above. Comparable.
I've since posted on the AC forums, but got merged with an old thread which I don't fully understand, they talk about setting bits - dunno where or how, though. Not yet, anyway.

This is the thread if you guys are interested:
http://www.assettocorsa.net/forum/index.php?threads/sli-how-to-get-the-best-performance.1416/


Ah, I've now read the thread more carefully, and here's how one changes things:

I'm using the latest version of NVIDIA Inspector (you can check for updates on the program itself). To edit AC profile, click on the "toolbox" icon next to your driver version, look for "Assetto Corsa" in the drop down menu in the top left, check that acs.exe is being considered in this profile and then change SLI Compatibility bits (DX1x) from 0x00000000 to 0x080210F5. Press Apply in the top right and you're good to go. You'll know it's working if when launching the game you get mad flickering from HDR for the first 10 seconds or so (while the camera spins around the car as it sits on the track).

but as he wrote it gets really flickery - altho the performance pretty much doubles, that's true

These are the values one can try:
0x000040F5 
0x080210F5
0x000110FB
0x080202F5

the last one does not work for at all, for me, the rest gives me the flickers.  I'll just wait till it's fixed.

[BJSRacer]

yawn..... 2:30am...... Steam Update.... McLaren MP4-12C...... who needs sleep

[Wally]

Seen this rank site? I don't know how it works, but it looks good.

http://www.radiators-champ.com/RSRLiveTiming/

[Wally]

Here you go, P45 at Mugello:

http://www.radiators-champ.com/RSRLiveTiming/index.php?page=rank&track=5&car=16

[Bruce]

Here you go, P45 at Mugello:

http://www.radiators-champ.com/RSRLiveTiming/index.php?page=rank&track=5&car=16

Nice work Wally, I see a Couple of sissies used anti-spin!
Looking forward to having a few laps when I get back.