SLI Sync Limit is at "1", and now my cards perform worse with SLI than alone.

[Nofew]

The subject says mostly everything. I've already tried contacting nVidia support, got all the way up to Level 2, and they don't know what's going on. I'm hoping somebody here does!

(Presumably relevant) system specs:

i7-3930k at 4.4 ghz

32 gigs of RAM

Asus Sabertooth-X79 motherboard

Asus Titan Black (Two in SLI using ribbon connector, stock vbios)

Below is an excerpt from the support log. I was particularly awake that night and I imagine it's more presentable than anything I can come up with at the moment.

(...)

The limit is only 172 while I run at 1440P. When I run at 1080p, I get limited to 300 FPS instead. 720p gets me 600. Changing the refresh rate does not change the framerate limit.

All these limits are set in stone; regardless if I'm running the newest benchmarks or the oldest games, the framerate limit doesn't change.

This is what lead me to believe that there's some sort of bandwidth issue somewhere. After turning every possible monitoring option on in MSI Afterburner, I found that PCIe Bandwidth was at 50% for each card (normally it's only at 10%), and the primary GPU was hitting "SLI Sync Limit". I can't find any information on what this means online because it's only mentioned tersely in a changelog in one place, but I figure it's relevant.

Now, you may be wondering why this is important -- I mean, logically, I'm still getting frames up faster than my display can draw them, right? The problem is, in games where I legitimately /need/ SLI, the performance is worse than if I turned SLI off entirely. I get 52 FPS in Fire Strike with SLI, and 58 without. I used to get about 110 with SLI.

I've made sure that the cards themselves aren't damaged. Before things broke, I remember running a benchmark on each card individually using software called "Cudahashcat". (I assure you, it was only to show people how fast short passwords can be broken in this day and age.) -- Each GPU got about 8 billion MD5 hashes per second. After things broke, I ran that again, and each card still pulls 8 billion.

I tried ordering a new SLI cable and switching it out, but that didn't change anything.

I'm not sure if the SLI connectors on the cards are okay. That's my only guess if it's something hardware related. I'm hoping it's something software-related though, obviously!

A few other things I've tried:

* Rebooting

* Clean install of the newest nVidia drivers (344.something -- I've updated since then to 344.65, but without clean installs)

* Different monitors

* Different connections (Tried DisplayPort and HDMI)

* Using Alternative Frame Rendering 2 rather than AFR1 (No change in framerate at all)

* Underclocking the CPU (No change. Note, I am only overclocking using the CPU multiplier, not BCLK)

* Toggling PCIe Spread Spectrum (No change, on or off)

* Leaving the computer off and unplugged until the capacitors ran out of power (Had to wait about two minutes until the LEDs on the motherboard went off)

* Blowing compressed air into the exhaust of both GPU's to remove dust (Not that either GPU gets excessively hot, but I was running out of ideas.)

* Different refresh rates (60, 85, 100, 110, 120, 144, G-sync on and off)

* Prayer. (Also prayed for my mother to get through surgery. That happened! Good thing God didn't choose to switch His answers!)

*EOF*

Does anyone even know what "SLI Sync Limit" even means, apart from something to with SLI and syncing?

[xaavbp]

Which pci port are you using on your card and is their any other card plugged in the pci slot if so it could just be that the pci is defaulting to a 8x 8x instead of a 16x, have you tried this with other games since this could just be a bad sli integration with this game

[Nofew]

Yes, I've tried other ports, other cards, and other games. Also, bandwidth between the motherboard and card clearly isn't the issue; read my original post over again.