I'm wondering if I just got unlucky in the silicon lottery, or if most of these can't hit the 1500 MHz boost clocks lots of the other 970s hit.
 
GPU: EVGA GTX 970 SC ACX 2.0
CPU: Xeon E3-1231v3
BOARD: Gigabyte GA-H81M-DS2V
PSU: Antec Neo Eco 620C (based on the Seasonic S12II 620w design, 576W on the +12V rail)
 
I can usually overclock this to a base clock of 1215 MHz which puts the boost at 1367 MHz, and GPU Boost usually takes this up to a constant 1418 MHz in most games. I usually add about 15mV to make these clocks stable, and they are in everything but Witcher 3, which I have to run at stock. When I'm gaming or running a benchmark the reason for the cap on the boost clock is always given as either power limit or voltage quality in GPU-Z, and even setting 110% power limit and 91C temp limit I can never get higher than 106.7% of TDP. This power supply is only a few months old and considered to be pretty decent quality (I only like using Seasonic units since they're always good at least 6 years in my experience). 
 
Are most people here who have the 2974-KR able to hit 1500 MHz? I wonder if I just got a lousy one, or if they're in general so-so overclockers due to power delivery. Or if perhaps using a 3+1 phase H81 board is causing a lot of ripple in the 75W the card is drawing from the PCIE slot? Maybe that's why I'm getting limited by the quality of voltage? I'd be really surprised if it's the PSU, since the 970 is a 165W card being run with an 80W CPU. My core temperature is usually 74C while gaming or 76C when running Firestrike, and I don't think I have ever seen it higher than 76C. My ambients are high, say 28C, since it's summer in Texas right now. I wonder if maybe the VRMs are overheating and that's what limiting my overclocking? If I set to anything higher than 1215 MHz base / 1367 MHz boost in MSI Afterburner I'll get the blackscreen / driver has reset crash often in Valley. The crash I get every couple of days in Witcher 3 1.07 though is a total system lockup.
 
Getting a Kraken G10 + AIO looks to be a waste since the 92mm fan isn't on the side of the card with the VRMs, and since my core temps are just fine.
 
What experience have other 970 SC ACX 2.0 owners had?

j2345912
It does sound like you may have gotten duds for overclocking. I don't have an ACX 970, however just curious if you have tried a custom fan profile with Afterburner. sacrifice a little noise, and see where your card lands when running 80-85%fan @ 69c & 100%@ 80. Keep it as cool as possible. Worth a shot anyway. I finally got a good batch of cards for overclocking, and can hit 1490Mhz with no added voltage, but I also run a custom fan profile, that some may consider "noisy". The fan profile is worth a shot, but it does sound like more voltage will be required on your end.

OK, I'll just blast the fans at 80% and run Firestrike and see if that changes anything. I guess that'll tell me if I'm getting boned by VRM temps. I'll come back and post results in a few minutes.

j2345912
sounds great! best of luck & no harm no foul! at least then you will know

Firestrike survived with an extra lousy 25 MHz to 1240 base / 1392 boost by cranking the fans to 80% lol. When I tried to give it another 25 MHz to 1265 base / 1417 boost the driver crashed to the desktop right at the end of the combined test (GPU boost was taking it to 1442 MHz). PerfCap reason was listed as Power, though it actually got to 111.9% TDP, never seen that before. I never even tried Valley since 25 MHz is pretty much nothing while 80% fans make me feel like I'm running an FX-5800 Ultra.
 

 
Man I wish I would have stepped up to the SSC with its 6+1 phase power when I had the chance. I almost wish the thing would get harmed, then I could send it in for warranty service and maybe they'd send me an SSC back!

j2345912
Lol@ the FX-5800 Ultra Reference! The 480's were just about as bad as the FX-5800 too lol
Anyway, like i always say, anymore all GPU companies seem to be pushing factory overclocks to the extremes. I think back when factory overclocks were like 25-50Mhz difference, now cards will boost well over 200Mhz faster then reference clocks. At the end of the day, chances are you will never notice the difference in game, so all is good The 970 you have is still a power house, and better then a lot can afford.
 

Yeah, it's definitely a tremendous GPU. I'm tempted to buy a second, an SLI board, and a 21:9 monitor, though if I get a second it will be a blower so I can put my SC in the lower slot and not have the upper one choked for air. Though I'll wait for November to see if more games start becoming Witcher 3 level hard to run. That's the only game I can't play ultra and get 60 fps locked at 1080p, I have to drop to mostly high with a few things like textures and water at ultra, but I still get drops to 55 fps.

While I cannot talk on the SC/SSC, I had to flash the Bio's on my 970 in order to overclock my 970 FTW to 1467 Boost clock.

Stock bio's EVGA provided capped my OCing by a max of just 25mhz. With the flash I was able to squeeze out 100Mhz and 125Mhz on memory.

Son of a *****, I just looked it up and apparently you can flash the BIOS without voiding the warranty if you have a dual BIOS card. But the SC isn't, the SSC is.
 

I just did a few passes on 3D Mark Fire Strike and had both of my 970 FTW+s running at 1573MHz if you were curious at how well these FTW+s and SSC+s can OC.

bsmegreg
I have a 2974-KR (SC ACX) and it doesn't overclock at all really. I can get it to clock 50mhz-100mhz higher at certain tasks, but then some games will end up crashing with various issues. So I just stay away from it as 10-30mhz doesn't do a lot for me.

Sounds about like mine. Most of the time I run it with a slight core bump to the FTW clocks, as I can notice a slight difference in GTA V with the extra 50 MHz. If I try for 100 MHz it never makes it through a run of Unigine Valley though.

OK, so my 970 SC sounds pretty much standard while everyone with SSC gets near 1500 MHz at least. D'oh, I was too happy with my 970 SC's performance to consider it would have only cost me a few bucks more to step up to a way better SSC. I'm way past the Step Up deadline since I never registered in the first 14 days and bought the card about 8 months ago lol.

Steve Grabowski

stalinx20
 
I have already done the whole ACX on SLI ( still am ). ACX in SLI for air is not an issue.

I have never done a multi card build before, but it seems like a lot of boards will put the top two PCIE-3.0x16 slots pretty close together so that there isn't a ton of room between the cards. And if I use any lower PCIE slots they're tied to the chipset instead of the CPU. Are your two 980s close together, or does you board give a larger distance between them?

 
There are some reviews of the ACX on youtube that talks exactly about what you're describing. You should look into it. If there is an inch GAP in between the 2 cards, you'll be just fine.
 
There are also some reviews that demonstrate 3 cards stacked like a sandwich that shows temps too.
 
Oh my apologies, I didn't answer your primary question. I have the X79 DARK and there is about 1.5" gap between both cards. If I decided to buy another 980, it would literally form a sandwich style SLI setup, and that is what most people are concerned with.
 
If you're concerned though, just get the blower style 970. It will work the same, but make sure you follow the compatibility chart and get the right blower style GPU that will work with your ACX card that you have now.