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Does it make a difference if faster card is put on the second PCI slot when doing SLI?

post #1 of 4
Thread Starter 
Hello everyone, ive never run SLI before so i want to ask this before doing anything, currently running EVGA GTX 980 Ti SC+ ACX 2.0+ which has boost clock of 1190 MHz, and going to put a KFA GTX 980 Ti HOF and it has boost clock of 1291 MHz.

My question is if it will be better if i put the 1291 MHz card on the first PCI slot and take the 1190 MHz one to the second slot, or it doesnt have any effect at all?

Thanks.
My gaming machine
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CPUMotherboardGraphicsGraphics
intel i7 6700 Asus Z170-A EVGA Geforce GTX 980 Ti SC+ ACX 2.0+ KFA2 Geforce GTX 980 Ti HOF 
RAMHard DriveHard DriveCooling
32GB Corsair Vengeance LPX DDR4 3000MHz Kingston SSDNow 240GB Western Digital Caviar Black 1TB Corsair H100i V2 
OSMonitorPowerCase
Windows 10 PRO 64-bit Acer Predator 165Hz, G-sync, 1440p, TN, 27" Corsair Rm 750x NZXT H440 
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My gaming machine
(12 items)
 
  
CPUMotherboardGraphicsGraphics
intel i7 6700 Asus Z170-A EVGA Geforce GTX 980 Ti SC+ ACX 2.0+ KFA2 Geforce GTX 980 Ti HOF 
RAMHard DriveHard DriveCooling
32GB Corsair Vengeance LPX DDR4 3000MHz Kingston SSDNow 240GB Western Digital Caviar Black 1TB Corsair H100i V2 
OSMonitorPowerCase
Windows 10 PRO 64-bit Acer Predator 165Hz, G-sync, 1440p, TN, 27" Corsair Rm 750x NZXT H440 
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post #2 of 4
Generally speaking: put the more powerful card in slot 1 (closest to cpu), and it will be used as primary.
There are some boards that this is not the case, and it might be best to refer to the manual for your motherboard to see the best way to setup SLI configurations.
Ol'Faithful
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Ol'Faithful
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Lite-On DVD-RW Noctua DH-14 CPU Cooler Windows 7 Pro x64 Samsung 24" LED 1080p 5ms DVI (S23A300B) 
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Thermaltake Toughpower 750W Gold Corsair M95 Onboard :S 
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post #3 of 4
Obviously, if you're gaming in non-SLI mode, the fastest card should be your primary. But in SLI it won't matter, as the cards are synced to the lower clock speed.

If you're running a tower case, with the first card on top, experiment and see which of the two cards runs cooler on top (since they're different coolers, and different quality chips and differing voltage bins).

Since neither of those cards are "blowers", almost ALL of the heat they generate is going to go UP before it goes out of the case, so the top card is getting soaked with the bottom card's heat, making it run hotter, always. And it may get hot enough to throttle boost clocks under heavy gaming or benchmark loads.
Edited by CroakV - 8/1/16 at 8:11am
post #4 of 4
Thread Starter 
I tried and swapped them yesterday, I put the faster card (KFA2 gtx 980 ti HOF) on top, but the gap was annoyingly too narrow between the two GPUs making it harder for the top card to have some airflow, so when i ran Heaven benchmark my top GPU's temperature hit 90 Celsius after a few minutes and i lost a few FPS, im guessing the card throttled to keep it from frying.

I swapped back when i saw that, and my top GPU's temps are around 82 at most, im guessing that is safe right?

As a side-note and off-topic, but I don't recommend the PC case I have, it is the worst case i have ever had, it looks very nice but the airflow is terribly bad, and the PSU place is hidden and there is no way to take that PSU cover off because it is soldered to the case itself, it was a pain in the butt just to connect the PCI cable when i was installing the other GPU, so if you want to install something and don't want to take out the whole parts out and cables (just because the stupid cover preventing you to work) then you have to use long tools and do funny things and rage for a few times, it made me want to crush the case with a sledgehammer and punch the people who designed it, what a bad design... i had Cooler Master Haf 912+ and i regret selling it, again, i don't recommend NZXT H440, stay away.
My gaming machine
(12 items)
 
  
CPUMotherboardGraphicsGraphics
intel i7 6700 Asus Z170-A EVGA Geforce GTX 980 Ti SC+ ACX 2.0+ KFA2 Geforce GTX 980 Ti HOF 
RAMHard DriveHard DriveCooling
32GB Corsair Vengeance LPX DDR4 3000MHz Kingston SSDNow 240GB Western Digital Caviar Black 1TB Corsair H100i V2 
OSMonitorPowerCase
Windows 10 PRO 64-bit Acer Predator 165Hz, G-sync, 1440p, TN, 27" Corsair Rm 750x NZXT H440 
  hide details  
Reply
My gaming machine
(12 items)
 
  
CPUMotherboardGraphicsGraphics
intel i7 6700 Asus Z170-A EVGA Geforce GTX 980 Ti SC+ ACX 2.0+ KFA2 Geforce GTX 980 Ti HOF 
RAMHard DriveHard DriveCooling
32GB Corsair Vengeance LPX DDR4 3000MHz Kingston SSDNow 240GB Western Digital Caviar Black 1TB Corsair H100i V2 
OSMonitorPowerCase
Windows 10 PRO 64-bit Acer Predator 165Hz, G-sync, 1440p, TN, 27" Corsair Rm 750x NZXT H440 
  hide details  
Reply
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