{"video_id":"fp_cbukIb7kTO","title":"Cooling a CPU from Both Sides","channel":"Linus Tech Tips","show":"Linus Tech Tips","published_at":"2025-04-19T17:07:00.035Z","duration_s":529,"segments":[{"start_s":0.0,"end_s":5.12,"text":"CPUs run hot. So hot that they would destroy themselves if it weren't for built-in protections","speaker":null,"is_sponsor":0},{"start_s":5.12,"end_s":10.48,"text":"that slow them down. But we don't want to slow down. We want to go fast and thus nerds are willing","speaker":null,"is_sponsor":0},{"start_s":10.48,"end_s":15.28,"text":"to spend hundreds of dollars to keep their CPUs cool. But what if there's a whole other side","speaker":null,"is_sponsor":0},{"start_s":15.28,"end_s":19.92,"text":"of cooling that no one's talking about? The back side, why not put a cooler there as well?","speaker":null,"is_sponsor":0},{"start_s":19.92,"end_s":26.8,"text":"So we did. Before you furiously comment saying, cooling a CPU from the back doesn't work, there's too many layers of stuff between the CPU and the","speaker":null,"is_sponsor":0},{"start_s":26.8,"end_s":31.04,"text":"cooler for it to be effective. Well take a look at this footage. That is heat on the back of the","speaker":null,"is_sponsor":0},{"start_s":31.04,"end_s":35.6,"text":"motherboard and there's enough that removing it might actually make a meaningful difference.","speaker":null,"is_sponsor":0},{"start_s":35.6,"end_s":42.72,"text":"So does it? And if it does, is it easy or cheap to do? Well that depends. Not until after this","speaker":null,"is_sponsor":0},{"start_s":42.72,"end_s":55.76,"text":"segue. To our sponsor. The simplest way to cool your CPU from both sides is to just","speaker":null,"is_sponsor":0},{"start_s":55.84,"end_s":61.28,"text":"point a fan at the back of it and that's been done before. My first PC case was the Antec 302,","speaker":null,"is_sponsor":0},{"start_s":61.28,"end_s":66.24,"text":"which had a mount for a fan right behind the motherboard tray. Did I spend 30 of my high","speaker":null,"is_sponsor":0},{"start_s":66.24,"end_s":71.68,"text":"school dollars on a Noctua fan to put it there? Yes. Did it do anything from what I remember?","speaker":null,"is_sponsor":0},{"start_s":71.68,"end_s":76.48,"text":"Kinda. So first things first, let's see if Antec was cooking or not. Noctua has this handy magnetic","speaker":null,"is_sponsor":0},{"start_s":76.48,"end_s":82.08,"text":"mount from their desk fan that we're just going to use just as a quick little preliminary test here.","speaker":null,"is_sponsor":0},{"start_s":82.08,"end_s":87.68,"text":"We're seeing about a degree or two difference going from like 51 point something to more","speaker":null,"is_sponsor":0},{"start_s":87.68,"end_s":93.36,"text":"closer to 50, 49.7 kind of area. And that lines up with the preliminary testing that we did","speaker":null,"is_sponsor":0},{"start_s":93.36,"end_s":98.64,"text":"taking measurements from the CPU and hardware info. But we all know that proper cooling requires","speaker":null,"is_sponsor":0},{"start_s":98.64,"end_s":104.64,"text":"contact. So let's see how easy or hard it is to mount a cooler on the back here. First things first,","speaker":null,"is_sponsor":0},{"start_s":104.64,"end_s":108.96,"text":"any mounting design that we make will need to make sure that the CPU cooler on the front","speaker":null,"is_sponsor":0},{"start_s":108.96,"end_s":114.16,"text":"isn't affected because spoiler alert, it's doing most of the work. And mounting hardware for CPUs","speaker":null,"is_sponsor":0},{"start_s":114.16,"end_s":118.64,"text":"is made with relatively tight tolerances to ensure that you can get even contact across the CPU's","speaker":null,"is_sponsor":0},{"start_s":118.64,"end_s":123.04,"text":"integrated heat spreader. And pretty much every part of the mounting hardware plays an important","speaker":null,"is_sponsor":0},{"start_s":123.04,"end_s":128.48,"text":"role, including the parts that go on the back of the motherboard, which are in our way. Let's get rid","speaker":null,"is_sponsor":0},{"start_s":128.48,"end_s":134.4,"text":"of it. And you know what else is in our way? The Intel socket backplate that holds the CPU","speaker":null,"is_sponsor":0},{"start_s":134.4,"end_s":139.36,"text":"retention ARM on the front. And that also prevents our second cooler from making direct contact with","speaker":null,"is_sponsor":0},{"start_s":139.36,"end_s":143.76,"text":"the back of the motherboard. So not only can we not get away with using out of the box CPU cooling","speaker":null,"is_sponsor":0},{"start_s":143.76,"end_s":148.96,"text":"parts for this, we're going to have to remove the backplate as well, which means that we're going","speaker":null,"is_sponsor":0},{"start_s":148.96,"end_s":155.76,"text":"to need to make a custom backplate. Yes. Originally, what I was thinking of doing is we could probably","speaker":null,"is_sponsor":0},{"start_s":155.76,"end_s":163.12,"text":"just modify the original backplate to add the cooler onto the back. However, as you can notice,","speaker":null,"is_sponsor":0},{"start_s":163.12,"end_s":168.32,"text":"there isn't really a whole lot of material on the ends to put the bolt holes through. I'd basically","speaker":null,"is_sponsor":0},{"start_s":168.32,"end_s":172.8,"text":"be drilling right along the edge here. So we're going to have to make a new one out of metal.","speaker":null,"is_sponsor":0},{"start_s":179.12,"end_s":183.36,"text":"Well, that's one thing I noticed. Oh, is that going to be a problem? They probably put this","speaker":null,"is_sponsor":0},{"start_s":183.36,"end_s":189.92,"text":"so there's a small thin layer insulation layer to probably make sure just in case","speaker":null,"is_sponsor":0},{"start_s":190.88,"end_s":195.36,"text":"that none of these traces or contacts. Oh yeah, because there's definitely open views there.","speaker":null,"is_sponsor":0},{"start_s":198.72,"end_s":203.2,"text":"So we plain just won't be able to get the same degree of contact on the back as we have on the","speaker":null,"is_sponsor":0},{"start_s":203.2,"end_s":208.16,"text":"front. First of all, we're on the wrong side. But second of all, this is not a flat surface like","speaker":null,"is_sponsor":0},{"start_s":208.16,"end_s":213.76,"text":"the cold plate on your cooler or the IHS on your CPU. There's a bunch of tiny electrical components","speaker":null,"is_sponsor":0},{"start_s":213.76,"end_s":217.92,"text":"that are going to prevent this cold plate from sitting flush with the back of the motherboard.","speaker":null,"is_sponsor":0},{"start_s":218.0,"end_s":221.28,"text":"What are we going to do about that? Well, we're going to need a cushioning layer that's a lot","speaker":null,"is_sponsor":0},{"start_s":221.28,"end_s":229.28,"text":"thicker than your typical thermal paste, like this one millimeter pad. Sadly, it has a worse","speaker":null,"is_sponsor":0},{"start_s":229.28,"end_s":234.16,"text":"thermal conductivity than any thermal paste. But hey, it's much better than air, which is what","speaker":null,"is_sponsor":0},{"start_s":234.16,"end_s":239.04,"text":"the fans are working with. So I'm just going to estimate it because like, is this got to be good","speaker":null,"is_sponsor":0},{"start_s":239.04,"end_s":243.52,"text":"enough? You know, that's what I always say is just got to be good enough. We decided to go with a","speaker":null,"is_sponsor":0},{"start_s":243.52,"end_s":249.6,"text":"mechanism that's just mounting into these corners that are already part of the Intel bracket because","speaker":null,"is_sponsor":0},{"start_s":249.6,"end_s":254.4,"text":"it just makes our lives easier. To mount in here, we had to make some custom length screws because","speaker":null,"is_sponsor":0},{"start_s":255.52,"end_s":260.32,"text":"I don't even actually know exactly what these holes are for on the Noxua coolers because I've","speaker":null,"is_sponsor":0},{"start_s":260.32,"end_s":265.36,"text":"never used them. I'm assuming it's compatibility with much older hardware, but I've never actually","speaker":null,"is_sponsor":0},{"start_s":265.36,"end_s":270.88,"text":"had to use them. So now I do. And it's what an exciting time for me. A new experience. Thankfully,","speaker":null,"is_sponsor":0},{"start_s":270.88,"end_s":275.44,"text":"there's Robertson screws in the precision screwdriver kit, which has an adapter that lets","speaker":null,"is_sponsor":0},{"start_s":275.44,"end_s":280.88,"text":"you lose any of those precision bits with the LTD screwdriver. Technically, the length of these","speaker":null,"is_sponsor":0},{"start_s":280.88,"end_s":286.64,"text":"screws should mean that nothing actually will screw into the motherboard, but there is a chance that","speaker":null,"is_sponsor":0},{"start_s":286.64,"end_s":293.68,"text":"like things can bow and bend a little bit. So I am going to be careful. I'm kind of trying to stop","speaker":null,"is_sponsor":0},{"start_s":293.68,"end_s":299.92,"text":"when I feel resistance out of just sheer terror because I am legitimately worried about this","speaker":null,"is_sponsor":0},{"start_s":299.92,"end_s":306.8,"text":"board existing. So let's, let's boot. If this seems simple, it's because Justin did all of the","speaker":null,"is_sponsor":0},{"start_s":306.8,"end_s":311.12,"text":"hard work, honestly. I mean, looking at it right now, we're still looking fine. It's not better.","speaker":null,"is_sponsor":0},{"start_s":312.24,"end_s":316.56,"text":"It's not worse. This is kind of interesting. So when we're looking through the thermal camera,","speaker":null,"is_sponsor":0},{"start_s":316.56,"end_s":324.72,"text":"we can see that our front CPU cooler is just much, much warmer overall than our back CPU cooler,","speaker":null,"is_sponsor":0},{"start_s":324.72,"end_s":329.44,"text":"which implies that it's moving away a lot more heat to be expected. But honestly, it feels like","speaker":null,"is_sponsor":0},{"start_s":330.56,"end_s":336.88,"text":"we haven't done much because the base of our CPU cooler is 20 degrees. So I don't think it's,","speaker":null,"is_sponsor":0},{"start_s":336.88,"end_s":341.36,"text":"it's doing much at all. So why doesn't the cooler perform better? Well, the motherboard is acting as","speaker":null,"is_sponsor":0},{"start_s":341.36,"end_s":344.64,"text":"an insulator, which slows the rate of heat transfer. And it doesn't matter how thermally","speaker":null,"is_sponsor":0},{"start_s":344.64,"end_s":350.08,"text":"conductive our CPU cooler or our thermal pad is, it can only remove the heat that reaches the other","speaker":null,"is_sponsor":0},{"start_s":350.08,"end_s":354.8,"text":"side of the motherboard. Think about it like this. It doesn't matter how many lanes your highway is","speaker":null,"is_sponsor":0},{"start_s":354.8,"end_s":359.92,"text":"if everyone has to file through the same single lane bottleneck. Support public transit. This cooler","speaker":null,"is_sponsor":0},{"start_s":359.92,"end_s":363.92,"text":"can only pull away as much heat as it's being given. But once you pull all of the heat away,","speaker":null,"is_sponsor":0},{"start_s":363.92,"end_s":368.48,"text":"you're going to be rate limited by the motherboard. So it doesn't matter how much extra cooling power","speaker":null,"is_sponsor":0},{"start_s":368.48,"end_s":372.16,"text":"you put in here unless you decide to go sub zero. And if you're going to go sub zero,","speaker":null,"is_sponsor":0},{"start_s":372.16,"end_s":377.68,"text":"just put it on the front. Don't put it on the back. I'm just going to take the fan out. I wonder","speaker":null,"is_sponsor":0},{"start_s":377.68,"end_s":382.0,"text":"if it will even like, the cooler will even saturate. Like that would be a good indicator","speaker":null,"is_sponsor":0},{"start_s":382.72,"end_s":391.92,"text":"if, if this thing is actually doing anything. 21.3. It's going up very slowly. So it is actually,","speaker":null,"is_sponsor":0},{"start_s":391.92,"end_s":394.96,"text":"we're transmitting some heat away, but you know, it's going to make this heat up faster","speaker":null,"is_sponsor":0},{"start_s":394.96,"end_s":398.96,"text":"as if I just touch it with my hand. Let's compare that to running the front without the fan. So","speaker":null,"is_sponsor":0},{"start_s":398.96,"end_s":402.4,"text":"we're looking at it right now. It's sitting at 27 degrees. Now Reese is going to hit","speaker":null,"is_sponsor":0},{"start_s":403.12,"end_s":414.72,"text":"Cinebench. And we're going to see how quickly this thing heats up. 28, 26, 29, 30. It's like,","speaker":null,"is_sponsor":0},{"start_s":414.72,"end_s":419.68,"text":"it took us like literally minutes to go up a degree before. And this is climbing","speaker":null,"is_sponsor":0},{"start_s":420.4,"end_s":423.76,"text":"a degrees per second. And eventually it will start getting to the point where it's probably","speaker":null,"is_sponsor":0},{"start_s":423.76,"end_s":428.72,"text":"thermal throttling. This just illustrates how much more important this is than whatever we're","speaker":null,"is_sponsor":0},{"start_s":428.72,"end_s":433.36,"text":"doing on the back. Keep watching, please. We decided to use our environmental chamber to","speaker":null,"is_sponsor":0},{"start_s":433.36,"end_s":438.56,"text":"have a perfectly controlled temperature for the most precise of results. But when we tested in","speaker":null,"is_sponsor":0},{"start_s":438.56,"end_s":444.4,"text":"there, every permutation of our system performed the exact same. Back panel, back fan, back cooler,","speaker":null,"is_sponsor":0},{"start_s":444.4,"end_s":449.52,"text":"stock cooler, it did not matter. Was all of our preliminary testing wrong? No, it's the environmental","speaker":null,"is_sponsor":0},{"start_s":449.52,"end_s":453.6,"text":"chamber who was wrong. To maintain temperatures within a tenth of a degree, the chamber needs to","speaker":null,"is_sponsor":0},{"start_s":453.6,"end_s":457.76,"text":"constantly blow conditioned air. And that conditioned air blowing was enough to cool the","speaker":null,"is_sponsor":0},{"start_s":457.84,"end_s":462.56,"text":"motherboard on our control system, which means that we saw no improvements on our cooled system.","speaker":null,"is_sponsor":0},{"start_s":462.56,"end_s":467.6,"text":"And that blows. We needed a more realistic airflow scenario. So we found a spot in our","speaker":null,"is_sponsor":0},{"start_s":467.6,"end_s":472.08,"text":"office that was roughly equidistant from a bunch of ventilation. We set the room temp to a tight","speaker":null,"is_sponsor":0},{"start_s":472.08,"end_s":477.6,"text":"22-ish degrees and tried again. And would you look at that? With the custom back plate and a fan,","speaker":null,"is_sponsor":0},{"start_s":477.6,"end_s":481.84,"text":"we see CPU temps drop one to two degrees. Heck yeah. And with our cooler mounted to the back,","speaker":null,"is_sponsor":0},{"start_s":481.84,"end_s":489.28,"text":"we see a further improvement of one or less degrees. It's not nothing, but it is almost nothing.","speaker":null,"is_sponsor":0},{"start_s":489.28,"end_s":492.72,"text":"Oh, and we've kind of been neglecting to tell you about the results that make this whole endeavor","speaker":null,"is_sponsor":0},{"start_s":492.72,"end_s":497.52,"text":"look even more foolish. When we compare CPU temps with our front mounted cooler on its","speaker":null,"is_sponsor":0},{"start_s":497.52,"end_s":501.84,"text":"stock mounting hardware, instead of our custom back plate, it performs better than our back","speaker":null,"is_sponsor":0},{"start_s":501.84,"end_s":506.88,"text":"mounted cooler setup. So all the haters at the start of the video who said this won't work,","speaker":null,"is_sponsor":0},{"start_s":506.88,"end_s":511.04,"text":"shut up. It does work. It just works poorly. Maybe you could get better performance out of","speaker":null,"is_sponsor":0},{"start_s":511.04,"end_s":514.8,"text":"a more precise custom mounting mechanism. But why bother when you can just do this?","speaker":null,"is_sponsor":0},{"start_s":517.04,"end_s":521.12,"text":"Or maybe you could just segue to our sponsor. Thanks for watching. What do you think? Was","speaker":null,"is_sponsor":0},{"start_s":521.12,"end_s":524.64,"text":"there something that we missed, something that you could have done differently? Let us know in","speaker":null,"is_sponsor":0},{"start_s":524.64,"end_s":528.24,"text":"the comments. And if you liked this video, why don't you watch a cooling solution that did work","speaker":null,"is_sponsor":0},{"start_s":528.24,"end_s":529.68,"text":"like our AC cooler?","speaker":null,"is_sponsor":0}],"full_text":"CPUs run hot. So hot that they would destroy themselves if it weren't for built-in protections that slow them down. But we don't want to slow down. We want to go fast and thus nerds are willing to spend hundreds of dollars to keep their CPUs cool. But what if there's a whole other side of cooling that no one's talking about? The back side, why not put a cooler there as well? So we did. Before you furiously comment saying, cooling a CPU from the back doesn't work, there's too many layers of stuff between the CPU and the cooler for it to be effective. Well take a look at this footage. That is heat on the back of the motherboard and there's enough that removing it might actually make a meaningful difference. So does it? And if it does, is it easy or cheap to do? Well that depends. Not until after this segue. To our sponsor. The simplest way to cool your CPU from both sides is to just point a fan at the back of it and that's been done before. My first PC case was the Antec 302, which had a mount for a fan right behind the motherboard tray. Did I spend 30 of my high school dollars on a Noctua fan to put it there? Yes. Did it do anything from what I remember? Kinda. So first things first, let's see if Antec was cooking or not. Noctua has this handy magnetic mount from their desk fan that we're just going to use just as a quick little preliminary test here. We're seeing about a degree or two difference going from like 51 point something to more closer to 50, 49.7 kind of area. And that lines up with the preliminary testing that we did taking measurements from the CPU and hardware info. But we all know that proper cooling requires contact. So let's see how easy or hard it is to mount a cooler on the back here. First things first, any mounting design that we make will need to make sure that the CPU cooler on the front isn't affected because spoiler alert, it's doing most of the work. And mounting hardware for CPUs is made with relatively tight tolerances to ensure that you can get even contact across the CPU's integrated heat spreader. And pretty much every part of the mounting hardware plays an important role, including the parts that go on the back of the motherboard, which are in our way. Let's get rid of it. And you know what else is in our way? The Intel socket backplate that holds the CPU retention ARM on the front. And that also prevents our second cooler from making direct contact with the back of the motherboard. So not only can we not get away with using out of the box CPU cooling parts for this, we're going to have to remove the backplate as well, which means that we're going to need to make a custom backplate. Yes. Originally, what I was thinking of doing is we could probably just modify the original backplate to add the cooler onto the back. However, as you can notice, there isn't really a whole lot of material on the ends to put the bolt holes through. I'd basically be drilling right along the edge here. So we're going to have to make a new one out of metal. Well, that's one thing I noticed. Oh, is that going to be a problem? They probably put this so there's a small thin layer insulation layer to probably make sure just in case that none of these traces or contacts. Oh yeah, because there's definitely open views there. So we plain just won't be able to get the same degree of contact on the back as we have on the front. First of all, we're on the wrong side. But second of all, this is not a flat surface like the cold plate on your cooler or the IHS on your CPU. There's a bunch of tiny electrical components that are going to prevent this cold plate from sitting flush with the back of the motherboard. What are we going to do about that? Well, we're going to need a cushioning layer that's a lot thicker than your typical thermal paste, like this one millimeter pad. Sadly, it has a worse thermal conductivity than any thermal paste. But hey, it's much better than air, which is what the fans are working with. So I'm just going to estimate it because like, is this got to be good enough? You know, that's what I always say is just got to be good enough. We decided to go with a mechanism that's just mounting into these corners that are already part of the Intel bracket because it just makes our lives easier. To mount in here, we had to make some custom length screws because I don't even actually know exactly what these holes are for on the Noxua coolers because I've never used them. I'm assuming it's compatibility with much older hardware, but I've never actually had to use them. So now I do. And it's what an exciting time for me. A new experience. Thankfully, there's Robertson screws in the precision screwdriver kit, which has an adapter that lets you lose any of those precision bits with the LTD screwdriver. Technically, the length of these screws should mean that nothing actually will screw into the motherboard, but there is a chance that like things can bow and bend a little bit. So I am going to be careful. I'm kind of trying to stop when I feel resistance out of just sheer terror because I am legitimately worried about this board existing. So let's, let's boot. If this seems simple, it's because Justin did all of the hard work, honestly. I mean, looking at it right now, we're still looking fine. It's not better. It's not worse. This is kind of interesting. So when we're looking through the thermal camera, we can see that our front CPU cooler is just much, much warmer overall than our back CPU cooler, which implies that it's moving away a lot more heat to be expected. But honestly, it feels like we haven't done much because the base of our CPU cooler is 20 degrees. So I don't think it's, it's doing much at all. So why doesn't the cooler perform better? Well, the motherboard is acting as an insulator, which slows the rate of heat transfer. And it doesn't matter how thermally conductive our CPU cooler or our thermal pad is, it can only remove the heat that reaches the other side of the motherboard. Think about it like this. It doesn't matter how many lanes your highway is if everyone has to file through the same single lane bottleneck. Support public transit. This cooler can only pull away as much heat as it's being given. But once you pull all of the heat away, you're going to be rate limited by the motherboard. So it doesn't matter how much extra cooling power you put in here unless you decide to go sub zero. And if you're going to go sub zero, just put it on the front. Don't put it on the back. I'm just going to take the fan out. I wonder if it will even like, the cooler will even saturate. Like that would be a good indicator if, if this thing is actually doing anything. 21.3. It's going up very slowly. So it is actually, we're transmitting some heat away, but you know, it's going to make this heat up faster as if I just touch it with my hand. Let's compare that to running the front without the fan. So we're looking at it right now. It's sitting at 27 degrees. Now Reese is going to hit Cinebench. And we're going to see how quickly this thing heats up. 28, 26, 29, 30. It's like, it took us like literally minutes to go up a degree before. And this is climbing a degrees per second. And eventually it will start getting to the point where it's probably thermal throttling. This just illustrates how much more important this is than whatever we're doing on the back. Keep watching, please. We decided to use our environmental chamber to have a perfectly controlled temperature for the most precise of results. But when we tested in there, every permutation of our system performed the exact same. Back panel, back fan, back cooler, stock cooler, it did not matter. Was all of our preliminary testing wrong? No, it's the environmental chamber who was wrong. To maintain temperatures within a tenth of a degree, the chamber needs to constantly blow conditioned air. And that conditioned air blowing was enough to cool the motherboard on our control system, which means that we saw no improvements on our cooled system. And that blows. We needed a more realistic airflow scenario. So we found a spot in our office that was roughly equidistant from a bunch of ventilation. We set the room temp to a tight 22-ish degrees and tried again. And would you look at that? With the custom back plate and a fan, we see CPU temps drop one to two degrees. Heck yeah. And with our cooler mounted to the back, we see a further improvement of one or less degrees. It's not nothing, but it is almost nothing. Oh, and we've kind of been neglecting to tell you about the results that make this whole endeavor look even more foolish. When we compare CPU temps with our front mounted cooler on its stock mounting hardware, instead of our custom back plate, it performs better than our back mounted cooler setup. So all the haters at the start of the video who said this won't work, shut up. It does work. It just works poorly. Maybe you could get better performance out of a more precise custom mounting mechanism. But why bother when you can just do this? Or maybe you could just segue to our sponsor. Thanks for watching. What do you think? Was there something that we missed, something that you could have done differently? Let us know in the comments. And if you liked this video, why don't you watch a cooling solution that did work like our AC cooler?"}