Disable nVidia SLI in Linux Mint KDE (v17.2) (dual-booting Windows 7)

This is copied/pasted from Reddit as my post there ended up being ignored. I figured I might be able to get some help here too, since this is a pretty darned tech-savvy community that isn't focused on one area.

(Source: https://www.reddit.com/r/linux4noobs/comments/3vhls8/disable_nvidia_sli_in_linux_mint_kde_v172/)

Begin Reddit post:

Greetings!

Long story short, I ended up with 2 EVGA GTX 970s with 4GB of VRAM
each, and I've currently got them installed in SLI. This is great for my
work in Windows 7, but upon booting to Mint, graphics drivers that
worked with only 1 gfx card don't work with SLI.

I've read online that there are major conflicts that make SLI
impossible without doing some hacking, and that this is a cross-distro
and cross-de incompatibility.

I noticed that when I first booted into Windows with SLI configured, a
message popped up asking if I wanted to run them in SLI, which I did,
so it quickly reconfigured them to run in SLI. This has me thinking that
maybe I can tell Mint to just use one graphics card and ignore the
other. I honestly have never messed with SLI before, so I don't know how
much is hardware and how much is software.
The main reason I haven't removed the second card yet is because the
dual-GPU is great for my design work, and I would prefer to keep the
configuration in Windows, but still have Linux function properly.
-Train

The issue still stands, so I would love some feedback. As a side-note, I'm between classes right now and won't be home for a few hours, so I won't be able to access the desktop computer in question for another 5 hours.

Thank you!

Is 1 card working in Mint, or the driver just won't work at all?

I run 2 980tis in SLI in Mint 17.2 & have never had any issues, it actually works better than it does in Windows. The second card only activates when I have a program running that supports SLI though.

Yup, 1 card on its own works perfectly. I've read a few places that say SLI is almost always troublesome for Linux OSes, so maybe you got lucky. Or maybe I just got unlucky...

My computer is packed away currently, as I'm about to move, so I can't compare settings for you at the moment.

Are you running the Nvidia drivers or Nouveau?

I'm using Nvidia-352 from memory.

The 2nd card will be off when I boot, but if I run something like Metro or Shadow of mordor, it will switch on.

I'm running an nVidia driver, can't remember which one, but I'll check when I get home in a couple hours. Now I'm starting to question the validity of the statements I read on SLI. Maybe they're just outdated but were correct when they were posted...

Well, I spent an hour trying driver after driver and had no luck. I just got back from a meeting I almost forgot about, and I think the verdict is to dismantle my SLI setup. At least I shouldn't have too hard of a time re-homing a barely-used 970, especially this time of year, since I can't return it.