{"video_id":"r3FbLjbXV1o","title":"Why Don't Multiple GPUs Scale Properly?","channel":"Techquickie","show":"Techquickie","published_at":"2017-05-06T14:58:16Z","duration_s":406,"segments":[{"start_s":0.24,"end_s":8.84,"text":"In your quest for the highest frame rates, the prettiest textures, and the","speaker":null,"is_sponsor":0},{"start_s":5.279,"end_s":11.719,"text":"most karma in the PC master race","speaker":null,"is_sponsor":0},{"start_s":8.84,"end_s":16.56,"text":"subreddit, you decided to go with a multi-GPU setup for your new gaming rig.","speaker":null,"is_sponsor":0},{"start_s":14.719,"end_s":22.16,"text":"But when you fire up your games, you notice that the sick gains you're","speaker":null,"is_sponsor":0},{"start_s":19.199,"end_s":28.16,"text":"getting aren't really what you expected, especially after","speaker":null,"is_sponsor":0},{"start_s":24.359,"end_s":30.8,"text":"dropping so much money on your system.","speaker":null,"is_sponsor":0},{"start_s":28.16,"end_s":37.36,"text":"So, what's the deal with that? Well, this problem has plagued PC gamers for","speaker":null,"is_sponsor":0},{"start_s":33.44,"end_s":39.76,"text":"over a decade. Why don't you usually get","speaker":null,"is_sponsor":0},{"start_s":37.36,"end_s":44.719,"text":"double the performance from a dual card configuration or triple if you have","speaker":null,"is_sponsor":0},{"start_s":42.079,"end_s":49.36,"text":"three video cards? I mean, since graphics rendering benefits from having","speaker":null,"is_sponsor":0},{"start_s":46.879,"end_s":53.52,"text":"more computing units in parallel, which you can learn more about in this video,","speaker":null,"is_sponsor":0},{"start_s":51.44,"end_s":59.199,"text":"by the way, wouldn't it make sense then for multicard setups like SLI and","speaker":null,"is_sponsor":0},{"start_s":56.079,"end_s":61.28,"text":"Crossfire to scale pretty easily?","speaker":null,"is_sponsor":0},{"start_s":59.199,"end_s":66.56,"text":"Unfortunately, it's not quite that simple. For starters, using two separate","speaker":null,"is_sponsor":0},{"start_s":64.239,"end_s":71.84,"text":"graphics cards means they have to talk to each other somehow. You see, most","speaker":null,"is_sponsor":0},{"start_s":69.36,"end_s":77.96,"text":"modern multiGPU setups use something called alternate frame rendering, where","speaker":null,"is_sponsor":0},{"start_s":74.56,"end_s":80.96,"text":"each card renders every other frame","speaker":null,"is_sponsor":0},{"start_s":77.96,"end_s":83.36,"text":"separately. Sounds efficient, but for","speaker":null,"is_sponsor":0},{"start_s":80.96,"end_s":88.479,"text":"them to be pushed to your monitor in the right order, the cards have to sync up","speaker":null,"is_sponsor":0},{"start_s":85.92,"end_s":94.64,"text":"properly, creating a surprising amount of overhead for both the GPUs and the","speaker":null,"is_sponsor":0},{"start_s":91.68,"end_s":100.4,"text":"electrical communication paths or buses that link them. This overhead not only","speaker":null,"is_sponsor":0},{"start_s":97.84,"end_s":106.159,"text":"gets worse as you add more cards to your rig, but can even result in a very","speaker":null,"is_sponsor":0},{"start_s":103.36,"end_s":111.2,"text":"unpleasant phenomenon called micro stuttering, which often shows up even if","speaker":null,"is_sponsor":0},{"start_s":108.88,"end_s":118.96,"text":"you're getting lots of frames per second. You see, for smooth gameplay,","speaker":null,"is_sponsor":0},{"start_s":113.84,"end_s":122.159,"text":"you need not only high FPS, but good and","speaker":null,"is_sponsor":0},{"start_s":118.96,"end_s":124.88,"text":"consistent frame times, which is the","speaker":null,"is_sponsor":0},{"start_s":122.159,"end_s":129.84,"text":"amount of time that a given frame will remain on your screen. Poor","speaker":null,"is_sponsor":0},{"start_s":127.6,"end_s":134.72,"text":"synchronization between the cards can leave certain frames on your monitor for","speaker":null,"is_sponsor":0},{"start_s":132.48,"end_s":139.36,"text":"way longer than they should be, even if the total number of frames each second","speaker":null,"is_sponsor":0},{"start_s":137.04,"end_s":143.36,"text":"is very high. This can render certain games","speaker":null,"is_sponsor":0},{"start_s":140.599,"end_s":149.36,"text":"unplayable, even though your setup is more than powerful enough to run it on","speaker":null,"is_sponsor":0},{"start_s":146.36,"end_s":151.68,"text":"paper. And as if that wasn't enough, an","speaker":null,"is_sponsor":0},{"start_s":149.36,"end_s":157.599,"text":"even bigger problem is that it's very difficult for your GPUs to know what","speaker":null,"is_sponsor":0},{"start_s":154.8,"end_s":162.959,"text":"frame to render next since it depends heavily on what the player chooses to","speaker":null,"is_sponsor":0},{"start_s":160.08,"end_s":169.44,"text":"do. The real time nature of game rendering makes it tough to parallelize","speaker":null,"is_sponsor":0},{"start_s":166.319,"end_s":171.84,"text":"in certain games among multiple GPUs,","speaker":null,"is_sponsor":0},{"start_s":169.44,"end_s":176.879,"text":"even with alternate frame rendering, as there isn't always a second frame or","speaker":null,"is_sponsor":0},{"start_s":174.239,"end_s":182.72,"text":"even part of a predicted one for your second card to work on. Of course, it","speaker":null,"is_sponsor":0},{"start_s":180.16,"end_s":188.0,"text":"isn't all about the inherent limitations of your hardware. On the software side,","speaker":null,"is_sponsor":0},{"start_s":185.84,"end_s":193.28,"text":"some game developers have been able to code their games in a manner that makes","speaker":null,"is_sponsor":0},{"start_s":190.319,"end_s":198.72,"text":"it easier for multiple GPUs to split the workload, while others simply don't","speaker":null,"is_sponsor":0},{"start_s":195.92,"end_s":205.36,"text":"bother. With the difficulty in coding for a very small subset of customers,","speaker":null,"is_sponsor":0},{"start_s":202.319,"end_s":208.0,"text":"many devs don't see the point in sinking","speaker":null,"is_sponsor":0},{"start_s":205.36,"end_s":213.12,"text":"tons of time into making sure that their games will play nice with multicard","speaker":null,"is_sponsor":0},{"start_s":210.159,"end_s":218.48,"text":"systems. Some games even manage to have worse performance in these situations.","speaker":null,"is_sponsor":0},{"start_s":216.159,"end_s":223.92,"text":"And finally, you definitely shouldn't run out and buy multiple GPUs if you're","speaker":null,"is_sponsor":0},{"start_s":220.959,"end_s":230.4,"text":"rocking a multiple monitor setup and you want extra video memory or VRAM to store","speaker":null,"is_sponsor":0},{"start_s":227.28,"end_s":232.799,"text":"all of your textures. With SLI and","speaker":null,"is_sponsor":0},{"start_s":230.4,"end_s":238.64,"text":"Crossfire, you are limited only to however much VRAM is on one card because","speaker":null,"is_sponsor":0},{"start_s":236.08,"end_s":243.2,"text":"both GPUs need to be able to access the same information in memory in order to","speaker":null,"is_sponsor":0},{"start_s":240.72,"end_s":248.56,"text":"work properly in tandem, whatever it might say on the packaging. So, does","speaker":null,"is_sponsor":0},{"start_s":246.159,"end_s":253.599,"text":"this mean then that SLI and Crossfire are useless gimmicks and a complete","speaker":null,"is_sponsor":0},{"start_s":250.48,"end_s":255.84,"text":"waste of money? Well, no. Multicard","speaker":null,"is_sponsor":0},{"start_s":253.599,"end_s":262.72,"text":"setups will give you the best possible performance in certain use cases and can","speaker":null,"is_sponsor":0},{"start_s":259.759,"end_s":267.6,"text":"even make some games playable at very high settings and resolutions where they","speaker":null,"is_sponsor":0},{"start_s":265.12,"end_s":272.24,"text":"wouldn't otherwise be, even with the best single card on the market. Not to","speaker":null,"is_sponsor":0},{"start_s":269.759,"end_s":277.12,"text":"mention that multiGPU rendering may improve with new APIs like Vulcan and","speaker":null,"is_sponsor":0},{"start_s":275.24,"end_s":282.639,"text":"DirectX12, which by the way you can learn more about here. Just do your","speaker":null,"is_sponsor":0},{"start_s":279.28,"end_s":284.639,"text":"research before you buy as to what games","speaker":null,"is_sponsor":0},{"start_s":282.639,"end_s":289.44,"text":"see the greatest benefit. And remember to keep your expectations realistic.","speaker":null,"is_sponsor":0},{"start_s":287.68,"end_s":295.28,"text":"After all, you wouldn't expect to be able to drive twice as fast just because","speaker":null,"is_sponsor":0},{"start_s":292.16,"end_s":297.12,"text":"you bought two cars, would you? Unless","speaker":null,"is_sponsor":0},{"start_s":295.28,"end_s":299.6,"text":"you're trying to do like a fan remake of Tokyo","speaker":null,"is_sponsor":0},{"start_s":300.44,"end_s":308.8,"text":"Drift. You guys know that I love Dollar Shave Club. We've been working with them","speaker":null,"is_sponsor":0},{"start_s":305.12,"end_s":311.199,"text":"for years. Good quality razors, good","speaker":null,"is_sponsor":0},{"start_s":308.8,"end_s":316.08,"text":"pricing, the shave is fantastic. But what you probably don't know is that","speaker":null,"is_sponsor":0},{"start_s":313.6,"end_s":318.96,"text":"they have other products, too. Well, though, if you watch our ad","speaker":null,"is_sponsor":0},{"start_s":317.12,"end_s":323.36,"text":"integrations, we talk a lot about their butt wipes. So, you probably are aware","speaker":null,"is_sponsor":0},{"start_s":320.56,"end_s":326.56,"text":"of those. But the point is, it's good stuff. They've got their Dr. Carver","speaker":null,"is_sponsor":0},{"start_s":325.039,"end_s":330.24,"text":"shave butter. They've got their aftershave. And they've got their one","speaker":null,"is_sponsor":0},{"start_s":328.4,"end_s":336.8,"text":"wipe charlies which make everything from your face all the way to not your face","speaker":null,"is_sponsor":0},{"start_s":333.759,"end_s":338.479,"text":"look and smell like a million bucks.","speaker":null,"is_sponsor":0},{"start_s":336.8,"end_s":343.199,"text":"Trust me guys, once you're in the club, you'll see they've got the best grooming","speaker":null,"is_sponsor":0},{"start_s":340.16,"end_s":346.16,"text":"products and they're affordable and even","speaker":null,"is_sponsor":0},{"start_s":343.199,"end_s":351.68,"text":"more importantly for nerds like me, it's easy. You don't have to go out of the","speaker":null,"is_sponsor":0},{"start_s":348.56,"end_s":353.28,"text":"house in order to look like you go out","speaker":null,"is_sponsor":0},{"start_s":351.68,"end_s":357.919,"text":"of the house. And you can even save money while doing it. I mean, it really","speaker":null,"is_sponsor":0},{"start_s":355.199,"end_s":362.0,"text":"is mindboggling, isn't it? The economics of being able to afford to have someone","speaker":null,"is_sponsor":0},{"start_s":359.759,"end_s":365.68,"text":"walk to your door and bring you these for less money than what you would pay","speaker":null,"is_sponsor":0},{"start_s":363.919,"end_s":368.479,"text":"to go out yourself and get them. I mean, that's how much margin those guys are","speaker":null,"is_sponsor":0},{"start_s":367.039,"end_s":372.639,"text":"taking from. Anyway, that's besides the point. Right now is your chance to see","speaker":null,"is_sponsor":0},{"start_s":370.72,"end_s":376.639,"text":"for yourself why so many of us love Dollar Shave Club. If you've never been","speaker":null,"is_sponsor":0},{"start_s":374.16,"end_s":380.479,"text":"a member before and you've never joined, now's the time. You'll get your first","speaker":null,"is_sponsor":0},{"start_s":378.08,"end_s":384.0,"text":"month of razors for free. Just pay the shipping and after that, it's only a few","speaker":null,"is_sponsor":0},{"start_s":382.24,"end_s":389.24,"text":"bucks a month. It's a limited time offer, so join today. Go to","speaker":null,"is_sponsor":0},{"start_s":386.6,"end_s":392.8,"text":"dollarshaveclub.com/Linus. That's dollarshaveclub.com/Linus. We've got","speaker":null,"is_sponsor":0},{"start_s":390.56,"end_s":395.759,"text":"that linked in the video description. Thanks for watching, guys. Like if you","speaker":null,"is_sponsor":0},{"start_s":394.24,"end_s":400.12,"text":"liked, dislike if you dislike. Check out our other channels. Comment with a video suggestion, and","speaker":null,"is_sponsor":0},{"start_s":398.52,"end_s":403.6,"text":"subscribe. Subscribe. If I wave my arms like this,","speaker":null,"is_sponsor":0},{"start_s":402.4,"end_s":406.96,"text":"maybe they'll subscribe. Maybe they'll do it this time.","speaker":null,"is_sponsor":0}],"full_text":"In your quest for the highest frame rates, the prettiest textures, and the most karma in the PC master race subreddit, you decided to go with a multi-GPU setup for your new gaming rig. But when you fire up your games, you notice that the sick gains you're getting aren't really what you expected, especially after dropping so much money on your system. So, what's the deal with that? Well, this problem has plagued PC gamers for over a decade. Why don't you usually get double the performance from a dual card configuration or triple if you have three video cards? I mean, since graphics rendering benefits from having more computing units in parallel, which you can learn more about in this video, by the way, wouldn't it make sense then for multicard setups like SLI and Crossfire to scale pretty easily? Unfortunately, it's not quite that simple. For starters, using two separate graphics cards means they have to talk to each other somehow. You see, most modern multiGPU setups use something called alternate frame rendering, where each card renders every other frame separately. Sounds efficient, but for them to be pushed to your monitor in the right order, the cards have to sync up properly, creating a surprising amount of overhead for both the GPUs and the electrical communication paths or buses that link them. This overhead not only gets worse as you add more cards to your rig, but can even result in a very unpleasant phenomenon called micro stuttering, which often shows up even if you're getting lots of frames per second. You see, for smooth gameplay, you need not only high FPS, but good and consistent frame times, which is the amount of time that a given frame will remain on your screen. Poor synchronization between the cards can leave certain frames on your monitor for way longer than they should be, even if the total number of frames each second is very high. This can render certain games unplayable, even though your setup is more than powerful enough to run it on paper. And as if that wasn't enough, an even bigger problem is that it's very difficult for your GPUs to know what frame to render next since it depends heavily on what the player chooses to do. The real time nature of game rendering makes it tough to parallelize in certain games among multiple GPUs, even with alternate frame rendering, as there isn't always a second frame or even part of a predicted one for your second card to work on. Of course, it isn't all about the inherent limitations of your hardware. On the software side, some game developers have been able to code their games in a manner that makes it easier for multiple GPUs to split the workload, while others simply don't bother. With the difficulty in coding for a very small subset of customers, many devs don't see the point in sinking tons of time into making sure that their games will play nice with multicard systems. Some games even manage to have worse performance in these situations. And finally, you definitely shouldn't run out and buy multiple GPUs if you're rocking a multiple monitor setup and you want extra video memory or VRAM to store all of your textures. With SLI and Crossfire, you are limited only to however much VRAM is on one card because both GPUs need to be able to access the same information in memory in order to work properly in tandem, whatever it might say on the packaging. So, does this mean then that SLI and Crossfire are useless gimmicks and a complete waste of money? Well, no. Multicard setups will give you the best possible performance in certain use cases and can even make some games playable at very high settings and resolutions where they wouldn't otherwise be, even with the best single card on the market. Not to mention that multiGPU rendering may improve with new APIs like Vulcan and DirectX12, which by the way you can learn more about here. Just do your research before you buy as to what games see the greatest benefit. And remember to keep your expectations realistic. After all, you wouldn't expect to be able to drive twice as fast just because you bought two cars, would you? Unless you're trying to do like a fan remake of Tokyo Drift. You guys know that I love Dollar Shave Club. We've been working with them for years. Good quality razors, good pricing, the shave is fantastic. But what you probably don't know is that they have other products, too. Well, though, if you watch our ad integrations, we talk a lot about their butt wipes. So, you probably are aware of those. But the point is, it's good stuff. They've got their Dr. Carver shave butter. They've got their aftershave. And they've got their one wipe charlies which make everything from your face all the way to not your face look and smell like a million bucks. Trust me guys, once you're in the club, you'll see they've got the best grooming products and they're affordable and even more importantly for nerds like me, it's easy. You don't have to go out of the house in order to look like you go out of the house. And you can even save money while doing it. I mean, it really is mindboggling, isn't it? The economics of being able to afford to have someone walk to your door and bring you these for less money than what you would pay to go out yourself and get them. I mean, that's how much margin those guys are taking from. Anyway, that's besides the point. Right now is your chance to see for yourself why so many of us love Dollar Shave Club. If you've never been a member before and you've never joined, now's the time. You'll get your first month of razors for free. Just pay the shipping and after that, it's only a few bucks a month. It's a limited time offer, so join today. Go to dollarshaveclub.com/Linus. That's dollarshaveclub.com/Linus. We've got that linked in the video description. Thanks for watching, guys. Like if you liked, dislike if you dislike. Check out our other channels. Comment with a video suggestion, and subscribe. Subscribe. If I wave my arms like this, maybe they'll subscribe. Maybe they'll do it this time."}