Hi everyone, this is my second post. Thanks for the feed-back on my "caught fire" thread.

I bought 2x 980ti FTW to have them work in SLI. I've read that only ports 1 and 2 can achieve that. My gpus are so close to each other, I fear that the heat could be a problem if I overclock or use them overtime. Do you think its best for me to just let go the SLI and put one of the gpus in 3rd slot so there's more space between the two? Or maybe it's just me freaking out with the spacing.

Thanks

I wouldn't worry about it too much right now because a GTX 980 Ti FTW has ACX 2.0+ Cooling as opposed to the more enclosed HSF (Blower style) Cooling as some cards shown in the list here have..Cards with blower style coolers benefit more from "breathing room" than cards with the more open ACX style coolers.
 
The most important/effective thing for cards with ACX Style Cooling is to have very good case ventilation/airflow because those things dump more heat inside the case whereas the blower style cards exhaust heat out the back.
 
Also realize that a GTX 980 Ti FTW has a QSD BIOS (Quick Switch Dual BIOS) that in the dBi BIOS position (the default position) the fans will turn off below 60C..With the QSD BIOS switch in the Performance position, the fans will run in Low RPM Mode below 60C to help with cooling during no/low load conditions as well as being enhanced for better overclocking potential, the Power Target is increased somewhat..There are people that don't know that, so just mentioning it.
 
Also, with the QSD BIOS in the dBi position, it is normal for the fans to 'twitch' under 60C when they are off, more on that here, so don't freak out and think something is wrong when you see them do that.
 
The Maximum GPU Tempurature specified by NVIDIA is 92C for a 980 Ti graphics chip, however, GPU Boost 2.0 will begin to throttle the card at about 80C in an effort to maximize the balance between performance/cooling/fan noise..You can overclock/make custom changes, including the Fan Speed Curve, using either EVGA PrecisionX or MSI Afterburner.
 
And as Cool GTX said, NVIDIA SLI requires that PCIe x16 slots run in at least x8 Mode.
 
Before removing your current Graphics Card/s, you should first remove the old drivers and optional driver components by running Display Driver Uninstaller (DDU) in Safe Mode and choosing the Clean and Shutdown option..Then install the 980s and the latest NVIDIA Driver..If you have any games 'Optimized' with GeForce Experience, I would 'Revert' them before running DDU.
 
Hope all this helps and you have trouble-free installation and operation of your new cards. 

I would undoubtedly and for sure roll with SLI in PCIe x16 slots 1 and 2 as long as you keep the PCIe x16 slot 2 running in at least x8 Mode and not x4 Mode going by the PCI-E Slot Breakdown described in the mobo manual..SLI won't work in slots running in less than x8 Mode as pointed out above, and using the other card dedicated to PhysX in an x4 Mode slot would be pretty much worthless.
 

Sure thing..You'd need a 40mm (2-way Short) bridge between slots 1 and 2, or just use the one that came in the box with your mobo..You can still use the 3-way/2-way bridge (100-3W-0032-LR) too if you want to, it'll just leave you with unused overhang on the bottom.

Mastercase 5 pro. Im using 2x 140mm fans on top. 2x 140mm front in addition of the h100i v2 and 1x 120mm back. I'm gonna try to post picture later. Looks like it doesnt work when I upload from my phone.

nordikstudio - I'm really curious how this works out for you as I too have been considering going dual 980Ti on a Classy K Mobo - and worry about the heat handling issue caused by the GPU cards being so close in proximity. 
 
You'd think EVGA would have considered such when designing the Mobo; unless they just licensed it from an OEM and put their branding on it.
 
bob16314 - I thought the 980s with ACX were like the 780s with ACX (I have one of those in a different machine), in that the fans on the card pull air into the card mounted radiators and exhaust that air out of the back of the PC through the vents in the slots where the connectors are... Am I wrong?
Are they pulling air in from back there and venting it into the case?
 
Ponder this with me...
I've been considering changing some of my fan's directions to help with case temp.  Not that it's super high right now but if I dual up and go SLI, I have no doubt it will get HOT in there. 
I'm using the Thermaltake Suppressor F31 case with solid left-side (no window), which is a huge case for a mid-tower and has lots of options for fans,  venting, etc. 
 
Currently, I've only got only one exit fan - the one in the typical spot in back, which is a Noctua 140mm. 
I also have a Noctua 140mm on the front and a Thermaltake 120mm up front right below it (drawing in, of course)
Another Thermaltake 120mm is on the bottom of the case blowing air up into the stream created by the front fans
And then one more Noctua 140mm is on the door vent - aiming (sort of) at the GPU area.
 
The CPU cooler is that monstrous dual 140mm fan Noctua D14, and draws air down toward the bottom of the case through the huge vented area up top - from which the 1st CPU cooler fan is only about 2" away at most. 
I wish (again that EVGA would have thought this through) - that the Mobo cooler mounts were oriented so that those fans blew towards the back of the case instead of up/down as the exhuast fan is right there...  But then again, that might completely dominate the exhaust fan leaving nothing in the way of pull for the case fans.
 
I'm wondering about reversing the CPU fans' direction - and maybe even mounting another fan up top to exhaust air up there too - so that the CPU is venting to the outside world and helping pull air out of the case overall; in the direction that heat travels... up. 
 
It seems to me that having 4 case fans and 2 CPU fans drawing in and only a single 140mm exhaust fan blowing out that air will be collected (high pressure) inside the case/system and cause more heat buildup than if there were more ways to exhaust it. 
At the same time, I also don't want to cause any stalling inside the case by misappropriating exhaust fan(s) or position, or otherwise interrupting efficient airflow for max cooling. 
 
Any thoughts on this guys?
I'm like nordikstudio in that I want to do what's best for the PC, and any help here will likely benefit us both.
Thanks!

I'm in the same spot as you guys. My specs are in my signature but I have yet to purchase a second 980TI Classy for fear of heat issues. I was thinking of just getting a 1080 FTW or Classy when it is released and not running SLI. I am also thinking of doing some mild OC on the CPU but have yet to get the system to boot when I enable the XMP profile. Anyone with tips on doing some mild OC they would be much appreciated. Sorry to hijack the thread and I will start another if you prefer that OP.

Just giving this a bump since it has some unanswered questions and some good advice.

@forgiven.one:
When I first installed the Mobo, I did some very mild OC just to play around but then set it back to stock for "production use" until I can get off the road long enough to sit down, study and keep the system stable.  I've got about 6 more weeks of hard travel and then I can take on heating the system up.
 
I'm attempting to remember... when I first started booting the system under an XMP profile, it seems like I got a failure as well and it turned out to be a switch in BIOS that I had incorrect and it sailed smoothly thereafter.  It seems like my memory voltage was defaulted to 1.2 and the switch I tripped was to set that to Auto, it then climbed to 1.385V and it's been booting fine ever since. 
 
Here's a photo of my Memory UEFI/BIOS page, if it helps you at all...
I wish I could be of more help and sure hope something sparks for you and you get it up to full mem speed. 
It sucks to have 3200 memory running at 1200 or so.  I've read where folks have OC'd this memory on Classy K Mobos to 3600 reliably - something I want to do when I get to OCing, just to learn more about this stuff.
 

forgiven.one
Thanks, I'll play around with those settings and report back what I find.

Just checking in to see if you had any interesting results to post.
I recently purchased a 2nd 980Ti Classy ACX2 but have not been off the road long enough to install it, much less play with any OCing.
Curious of your findings.