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  1. #1
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    Top-mounted vs. Bottom-mounted PSU's

    What exactly are the pros and cons to top-mounting and bottom-mounting your PSU?

    I've been seeing a lot of cases lately where PSUs are mounted at the bottom of the case, and been kind of wondering why one would want to do that.

    Personally, I've always top-mounted mine because for one thing, it's what I'm used to doing. Growing up I never saw a case that didn't have a PSU that was mounted at the top, and to me it seems to make logical sense to mount it there since warm/hot air rises.
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  2. #2
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    Looks, really. It may also work better with the design of the case. For example, if you have the power supply up top, you can't really put a lot of fans up there or fit a large radiator. Putting it on the bottom saves a bit of "wasted" space.

    Heat wise, it won't really matter with only a few degrees difference in a well-ventilated case. Cable routing can be difficult with short cables when it is mounted on the bottom, namely the 4/8pin CPU ATX. Once nice positive that I noticed on my first bottom-mounted case is it wanted to keep standing up, rather than tipping over easily.

    I wouldn't decide on a case purely by power supply location. There are a lot more important factors.
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  3. #3

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    Quote Originally Posted by Tech Tweaker View Post
    What exactly are the pros and cons to top-mounting and bottom-mounting your PSU?

    I've been seeing a lot of cases lately where PSUs are mounted at the bottom of the case, and been kind of wondering why one would want to do that.

    Personally, I've always top-mounted mine because for one thing, it's what I'm used to doing. Growing up I never saw a case that didn't have a PSU that was mounted at the top, and to me it seems to make logical sense to mount it there since warm/hot air rises.
    Tech,

    I also had my reservations on bottom mounted power supplies. Too much engineering and testing goes into cases, so with that in mind and the observations Thideras makes (lengths of the 4/8pin CPU ATX), this Coolermaster NV 690 case is bottom mounted. As long as you keep it elevated on a firm surface with the mounting feet that comes with them for air flow, you'll never look back.

    My 8-pin CPU cable just made it but with short extensions available if you need one, it's not a problem. Most larger power supplies have longer cables than mine.
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  4. #4
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    You couldn't pay me to have a top mounted. Biggest reason is they are very heavy components and I don't want my center of gravity that high. Second, heat is usually exhausted near the top and I don't want my psu up top because then it's going to be hotter resulting in it being louder. Since most psu exhaust out the rear then they wont heat the system up.

    It just seems logical to me.to have the heaviest components at the bottom.

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  5. #5
    Member DSM4Life's Avatar
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    I am 100% happy with my bottom mounted PSU. Not only does the PSU now get clean cooler air, pulling from the outside air instead of the warm in case air but it helps with my CPU air flow.

    As you can see in the 2nd pic the air flow comes in , goes straight across the case and his the other fan without and restriction or PSU pulled any of the air in.

    Its just my opinion but i prefer the bottom mounted PSU's now.

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  6. #6
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    Quote Originally Posted by thideras View Post
    Looks, really. It may also work better with the design of the case. For example, if you have the power supply up top, you can't really put a lot of fans up there or fit a large radiator. Putting it on the bottom saves a bit of "wasted" space.

    Heat wise, it won't really matter with only a few degrees difference in a well-ventilated case. Cable routing can be difficult with short cables when it is mounted on the bottom, namely the 4/8pin CPU ATX. Once nice positive that I noticed on my first bottom-mounted case is it wanted to keep standing up, rather than tipping over easily.

    I wouldn't decide on a case purely by power supply location. There are a lot more important factors.
    Hmm... Oddly, that's something I hadn't thought of. Putting it lower in the case, thereby lowering the case's center of gravity by making it less top-heavy and making it more stable in the process.

    I figured it was just a personal preference kind of thing.
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  7. #7
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    Quote Originally Posted by Black C5 Z06 View Post
    You couldn't pay me to have a top mounted. Biggest reason is they are very heavy components and I don't want my center of gravity that high. Second, heat is usually exhausted near the top and I don't want my psu up top because then it's going to be hotter resulting in it being louder. Since most psu exhaust out the rear then they wont heat the system up.

    It just seems logical to me to have the heaviest components at the bottom.
    Personally, I kind of like the idea of the PSU acting as a way to exhaust the heat within my case. If my PSU were mounted at the bottom, hot air would most likely collect at the top of my case, and with nothing to exhaust that air it would stay in the case longer, thus increasing the internal temp and possibly causing my components to run hotter.

    I've had two top-mounted PSUs and I've never noticed either even get slightly warm to the touch, so I can't imagine that what warm air does go through them is enough to increase their temps by a noticeable amount.

    I agree about putting the majority of the weight at the bottom of one's case being a good thing though.
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  8. #8
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    Quote Originally Posted by DSM4Life View Post
    I am 100% happy with my bottom mounted PSU. Not only does the PSU now get clean cooler air, pulling from the outside air instead of the warm in case air but it helps with my CPU air flow.

    As you can see in the 2nd pic the air flow comes in , goes straight across the case and his the other fan without and restriction or PSU pulled any of the air in.

    Its just my opinion but i prefer the bottom mounted PSU's now.

    There is a problem with those pictures though, the front intake is mounted at the top of the case, but in most cases it is normally at the bottom (in all of the cases I've seen anyway).

    With that layout in mind in most bottom-mounted cases the air from the front fan slams into the front of the PSU (with some of it always being exhausted from the case before the rest goes around the PSU).
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  9. #9
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    The bottom psu mounting seems to be the new trend for case designers these days. I think top mounted is a design that older pcs used.
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  10. #10
    Member DSM4Life's Avatar
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    Quote Originally Posted by Tech Tweaker View Post
    There is a problem with those pictures though, the front intake is mounted at the top of the case, but in most cases it is normally at the bottom (in all of the cases I've seen anyway).

    With that layout in mind in most bottom-mounted cases the air from the front fan slams into the front of the PSU (with some of it always being exhausted from the case before the rest goes around the PSU).
    I used that as a general example. I have a fan mounted at the top and bottom so my specific case is setup like this :



    The air that hits the CPU is straight through no restrictions.
    The cool air coming in from the bottom isn't really hitting the PSU but its being sucked up by the heatksinks on the GPU (green) then exhausted. There is also another intake in the side housing to blow more cool air onto the video card.
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  11. #11

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    Both methods work fine. Each case is different and your style of overclocks may require adjustments in fan positions or adding a few. Fortunately with my rigs, heat isn't a problem with my mild overclocks and moderate non-overclocked GPU.

    The only thing I did with this case was position a fan on top of the DVD drive in the upper bay to blow a little air on the RAMs. It may help the CPU also, I don't know that. I don't even use the side panel or floor fans.

    Bottom mount power supply pulls the air in and then out the back with none passed up onto your GPU and upper case. Top mounts usually pull some warm air into the power supply and then out the back. Thideras' explanation of having the weight bottom mounted is very accurate too, I'm liking it.
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  12. #12
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    Yeah, I am testing a case with a bottom mounted psu right now and it definitely lowers the CG of the case. But as far as ventilation is concerned, a case with proper ventilation designed into it doesn't really care if the psu is at the top or the bottom. And if the case has good ventilation, the part about hot air rising to the psu is a non-issue, as the air won't be hot enough around it to make much difference one way or another.

    I'm not giving away what case I am reviewing (review coming shortly), but I actually saw a little over 1 C increase in cpu temps between it and the old, modded Antec 1040 clone I have been using for heatsink tests. That is with the same components and heatsink and the same heatsink mount as in the old case. I didn't disturb the mount on it when transferring everything into this new case. Does that mean this new case is a bad design? No, it's actually got decent ventilation and very nice features, but the old Antec case that I had modded with larger exhaust fans seems to get rid of hot air from the cpu area just a tad better than it.

  13. #13
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    I like my Antec 300 case. It has an exaust fan @ the top to compensate for bottom-mount PSU position. IT stays very cool.
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  14. #14
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    Bottom mounting PSU has happened because a cooler PSU is a more efficient PSU. Not having warm air to suck in from your GPU/CPU etc helps increase efficiency slightly. Also the fan has to spin less to compensate for that 'second hand heat'.
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  15. #15
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    I find a bottom-mounted PSU far easier to deal with, to be honest. It makes cable management easier. That is, unless someone (cough Asus cough) decides to put the ATX power connector exactly halfway up the board, near the back of the case.
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  16. #16
    Quote Originally Posted by Theocnoob View Post
    Bottom mounting PSU has happened because a cooler PSU is a more efficient PSU.
    Do you think their would be a measurable difference in PSU efficiency with the mounting positions in the same case with all the same hardware. It sounds logical to me, but it just seams so small a temperature difference, as to effect efficiency in a properly vented cases, like I bet most of us here have
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  17. #17

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    Quote Originally Posted by David View Post
    I find a bottom-mounted PSU far easier to deal with, to be honest. It makes cable management easier. That is, unless someone (cough Asus cough) decides to put the ATX power connector exactly halfway up the board, near the back of the case.
    David,

    The Cable Management threads and photos here are excellent and they are what influenced me with a bottom-mount case after I saw what could be done with them, and those Asus boards stuck out like a sore thumb.........
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  18. #18
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    Everywhere? Seriously, there are a ton of them.

    Start here: http://www.overclockers.com/forums/s...ble+management
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