 SLI in a nutshell is a way of using more than one graphics card at a time for a richer gaming experience with higher frame rates and More in-game eye candy turned on you can learn more about it in this video here on tech quickie now Nvidia's website is full of Certain information about SLI technology which graphics cards support it where to buy the other hardware you need guides on how to set it up, but I noticed that beyond one specific Specific two-way SLI configuration at one specific resolution They don't seem to even want to talk about the value proposition of adding in more cards or how performance scales in relation to the cost as you put more and more graphics cards in your gaming PC So when a unique opportunity fell into my lap to test two-way three-way and four-way SLI with the brand spanking new GTX 980 at 4k I jumped on it Corsair gaming RGB keyboards feature precision Cherry MX RGB key switches for 16.8 million color per key backlighting for virtually unlimited customization click now to learn more I'm gonna jump right into numbers here because they actually only tell part of the story I tested four games with details cranked at 4k resolution on a gigabyte x99 gaming 5 with the core i7 4930k 6 core at 4 gigahertz and 16 gigs of 2400 megahertz DDR4 memory And then I threw a Corsair ax 1500i power supply on the bench because I was concerned about power consumption and overwhelming the existing one But more on that later So let's start with what should be the poster child for multi-way SLI tomb Raider 2013 if all you do is hang around and play tomb Raider go buy for GTX 980s hell buy an extra one to keep on your desk to remind you of how great it is you get 30 FPS average with One card then 23 to 24 more frames per second with each additional card Almost the same scaling going from 1 to 2 2 to 3 and 3 to 4 cards and on top of that the animations are butter smooth With no perceptible micro stutter outstanding It's just too bad not every game is like this if tomb Raiders the poster child watch dogs is the one in the corner with the Dunce hat scaling from 1 GPU to 2 seems okay at first glance if we only look at average frame rates But minimum frame rates tell a bit more of the story they dropped almost in half and this Hitching and stuttering was very noticeable in game It actually gets worse the more graphics cards you add yet another issue for the PC version of watch dogs Next up is far cry 3 Something unusual you might notice about this game is that the minimum frame rates are very close to the average frame rates in some cases This is because our run for this game involves driving around a track running over dudes and getting shot at and looks very consistent Having minimum and average frame rates close to each other makes animations appear very smooth on screen At least with one or two GPUs installed in the system Even though average frame rates scale very well with more GPUs You can see that minimums don't and this manifests as uneven Inconsistent movement of objects on screen with three or four graphics cards our last game is crisis 3 Just like far cry 3 it scaled well from 1 to 2 GPUs But we see the same issue with great average frame rate scaling and poor minimum frame rate scaling that translates to uneven lurchy Animations in the case of crisis 3 it was actually noticeably worse than far cry 3 with three-way and four-way SLI So much so that as a gamer I would much rather play with two graphics cards at lower detail settings than with more graphics cards and game settings cranked Speaking of in-game settings if you want to see how I was running everything check out the download link in the video description GPU boost clock speed was another interesting part of the story with two GPUs We saw slightly lower turbo speeds because we hit our thermal limit sooner on the top card than the bottom one Because it has less access to fresh air surprisingly though We reached the same GPU speed even in the other Configurations pretty impressive when they're all packed in like sardines in a four-way config speaking of impressive power consumption I mean I mentioned before I threw a 1500 watt 80 plus titanium PSU in this rig to ensure that I wouldn't be limited The fan on it barely even turned on our four-way SLI configuration drew 620 watts from the wall in our stare at the fire test in Far Cry 3 that means that even accounting for another 50% capacity for future expansion a Thousand watt power supply would have been plenty for this rig, so it's back on the bench All right now back up a second line as you run in here throw a bunch of graphs in our faces for five minutes and then basically Voice-over telling us to ignore the performance numbers because they don't reflect the gameplay experience what gives great question Normally when we do benchmarks on this channel It's okay to use fraps to take average frame rates and compare graphics cards relative performance Because in our game showdowns and our graphics card reviews we only test single GPU configurations with multi GPU configurations Particularly beyond two-way as I've been discussing in this video Different measurements need to be taken to evaluate the evenness of the pace with which new frames are delivered to the gamer Here's an example the video you're watching right now is playing at 30 frames per second smooth Hold on a second. What was that? We only dropped the frame rate 3% to 29 frames per second But because we're doing this by dramatically increasing the delivery time of just a few frames periodically You're seeing very noticeable hitches and stutters aren't you that's what I'm talking about now Unfortunately, we don't have the equipment to objectively measure the perceived smoothness of a game like you'll see on some of the hardcore Tech sites like PC per and tech report. I recommend reading up on those sites by the way Search for frame pacing if you want to learn more about this But the good news is that in the case of our multi-way SLI video today at least with this new and relatively immature Driver for the GTX 980 it was easy to pick up on this stuff with the naked eye So being able to measure it wouldn't have changed the conclusion much and here it is What we've been saying for years is still true One of the fastest GPU you can afford is best in most cases because you'll always get the performance you paid for even in watchdogs Until you get up to the top tier cards at which point two of them might make sense if you really are hungry for more Performance but beyond that things really come off the rails in a hurry And I guess I can see why Nvidia offers users the capability to run more cards if they want to but didn't even have Any three-way or four-way configs running even in their own demo systems at the GTX 980 launch event? 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