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 Post subject: Mounting a CPU heatsink without the backplate
PostPosted: Thu Aug 21, 2014 11:28 am 
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Hello everybody,

I would like your advice on whether it's safe to mount a large (1Kg) CPU heatsink on a motherboard, but without mounting the heatsink backplate. The motherboard would stay on a horizontal plane. Has anyone done something like this?

My problem is that I would like to use an Asrock Z97E-ITX motherboard, as it has all the features I want, in a tiny package, and at a very reasonable price (compared to the micro-ATX options), but I want to use the huge Nofan CR95-C on it. The Nofan has a backplate which unfortunately can not be mounted, because of an IC on the motherboard which is in the way (the one pointed to by the arrow in the image below):
Image

The NoFan backplate looks like this:
ImageImage

I did not buy the motherboard yet, but I used a photo of the back of the motherboard to make the test, and while I can safely use some PVC insulating tape on the upper and lower margins of the backplate to prevent shorts on the solder points, there's nothing I can do about the IC. Half of that IC ends up under the backplate.

That's why I'm considering not mounting the backplate at all. The motherboard would be placed horizontally in an open case, and the NoFan heatsink on top of it. This means there would be no lateral forces exerted on the motherboard, like when the motherboard is placed vertically. But I still don't know if the pressure on the mounting holes would not be too much without the backplate.

Perhaps somebody else tried this with some other CPU heatsink, and can share his experience (or knows whether the amount of force that would be exerted by the nuts and screws is known to be not safe without a backplate) ? :)


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Thu Aug 21, 2014 12:27 pm 
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Thermalright stopped supplying a backplate for one of their socket 1150 coolers, providing fixing bolts only. Part of the reason is that 1150 sockets already have a backplate so the case for a second one can be questionable. For what you have in mind the 1150 backplate on its own may well be sufficient. If you use just the bolts it is a sensible precaution to use a nylon washer under them to make sure there is no chance of a short.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Aug 24, 2014 3:37 am 
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Thanks, that's good to know. :)

Now, the only issue remaining is my indecision in whether to pursue this option, which really limits me to open-air cases, as the NoFan size makes it impossible to find any closed case that would fit it when placed on that motherboard. Or just go for the safer microATX options, but with less features and more expensive...

That tiny Z97E-ITX is not only feature rich, but has components fit for fanless operation: second-best VRM mosfets on the market with very low amount of heat generated during operation and similar top-notch induction coils, plus high-temperature resilient caps. If I were to look for the same quality of components in micro-ATX boards, I would have to pick the ASUS Rog Gene VII board, which is so overkill, not to mention so much more expensive, and doesn't even have a DisplayPort output to future proof it for some 4K playback... (and I also found a review that mentioned it BSODs after some time when running Prime95 for hours in a "no airflow over the motherboard" scenario).


Sources for VRM components quality, for anyone interested (for fanless operation, what's better are mosfets that dissipate a smaller amount of heat for the same current than other mosfets):
http://www.overclock.net/t/1490142/z97-vrm-info
http://www.sinhardware.com/index.php/vrm-list


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Aug 24, 2014 4:34 am 
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bbalex wrote:
the NoFan size makes it impossible to find any closed case that would fit it when placed on that motherboard.

What about something large, like the Cooltek/Rosewill/Jonsbo W1 ?

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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Aug 24, 2014 8:18 am 
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I would cut out a piece from the back-plate, alt drill out a bit if that works, so that the IC would fit. I would not use a 1Kg cooler without having it firmly secured not even in a horizontal mount.

If you decide to go ahead with cutting or drilling make sure you carefully sand the edges and clean it afterwards. You want to make sure there are no metal shavings.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Aug 24, 2014 8:23 am 
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id say no back plate is fine, so long as you do not transport the PC with the heatsink installed.

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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Mon Aug 25, 2014 2:55 am 
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walle wrote:
...I would not use a 1Kg cooler without having it firmly secured not even in a horizontal mount.
The NoFan Cr-95C actually weighs 730 g which would put it into the same weight category as some conventional push-pin (non backplate) CPU coolers. For example Scythe had the Yasya push-pin cooler which weighed 825 g with fan and this did not seem to cause any issues not even with cooling efficiency.

Another option with the NoFan Cr-95C would be to replace the supplied backplate with one of the third party versions which goes over the 1150 plate and does not touch the back of the motherboard at all. The NoFan fitting uses long spring-loaded spacers with a screw fitting at the motherboard end which might complicate this but it could be worth looking at.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 3:30 am 
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quest_for_silence wrote:
bbalex wrote:
the NoFan size makes it impossible to find any closed case that would fit it when placed on that motherboard.

What about something large, like the Cooltek/Rosewill/Jonsbo W1 ?

The reason why I don't expect any closed case to fit this motherboard with the NoFan mounted on it, is because there is not enough clearance around it.

This is how the NoFan would look like on top of the ASRock Z97E-ITX:
Image

I used 183mm as the diameter of the NoFan, and made pixel measurements given the standardized locations of the motherboard and socket mounting holes. The photo is the one used by ASRock on their product page, and shows a little bit of distortion on the vertical features, but it's spot on when comparing items at the motherboard height level. Because of that, the heatsink circle has to be compared with the motherboard edges, and not with the vertical I/O connector features.

The NoFan overhangs the top of the motherboard by ~39.23mm, which might seem a lot, but there are cases which can fit that. I did pixel-based measurements on the Thermaltake Core V1 and Corsair 250D, and they are ok. These cases even fit the 147mm height of the cooler, even though they claim to fit only up to 140mm. And they have a top window which I can remove, so that I can passively cool the CPU thanks to the ventilation holes in the side panels.

But the problem is the overhang on the motherboard shield side. The NoFan needs an additional ~4.14 mm. Unfortunately, that's too much. The microATX spec says that the allowed distance from the motherboard edge till the chassis inner-side is 2.11 +/-0.25mm. That's only half of the 4.14mm I need. What can I say... "death by mm"! :cry:


Perhaps I did some mistakes, or perhaps the chassis manufacturers are making them with even worse tolerances and I would get lucky enough to receive one of them... or maybe I could enlarge the motherboard mounting holes by a few mm, till it all fits. I don't know, it looks like a lot of trouble. I'm also afraid the NoFan would touch the chassis and maybe that could short and fry something.

I am still not sure what to do about this.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 3:49 am 
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It is pretty obvious that in order to use a big cooler you'll need a big case nad a big enough Mobo. This is like you won't fit a V8 Hemi in a Smart 2 seater's motor compartment.

To play this one save, i'd suggest sticking to NoFan recommendations for compatible hardware, so you might check out their support pages first.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 4:03 am 
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To be fair to NoFan they do publish a motherboard compatability list, including this section for Asrock and there are a lot of boards on the list. The Z97E-ITX is not one of them; if you want to use this cooler a change of motherboard choice will be required. If the Z97E-ITX must be kept then maybe rethink CPU cooler choice. The Noctua NH-L12 for example will work with this board. Used in PWM mode under idle/low system stress conditions this cooler will be very quiet, effectively silent.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 4:15 am 
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Where is the fun in following the manufacturer recommendations though! :D

Still, this was so close... just 2-3mm and it would have worked.

I was already thinking that a tiny case like the Core V1 which still fits a GPU card, would have been the perfect small semi-passive build: fanless operation most of the time (with the Palit KalmX or a Strix in there), and safe gaming when placing the window cover back over the top panel and letting that big front fan spin.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 4:29 am 
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bbalex wrote:
I was already thinking that a tiny case like the Core V1 which still fits a GPU card, would have been the perfect small semi-passive build: fanless operation most of the time (with the Palit KalmX or a Strix in there), and safe gaming when placing the window cover back over the top panel and letting that big front fan spin


People have done this, but used a Macho or similar cooler. If i remember correctly, there are some builds with such a semi-passiv setup or using the back exhaust fan to cool the then fanless Macho.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 4:58 am 
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I'm not convinced of the ability of the Macho or HR-22 to safely keep the CPU cool, in fanless operation with no fan spinning, and only convection cooling. The test here on SPCR showed that the temperature just kept on raising, till the CPU finally throttled. The NoFan was the only one that kept the temperatures stable. And my own experience with a i7 4770S is that it's stable at idle at around ~40 degrees C, and under max load (Prime 95 Small FFTs and Futuremark) it's stable at 82-84 degrees C - but that's close to the throttling limit. If the NoFan is barely safe under such conditions, the Macho or HR-22 are probably not safe at all.

One interesting bit that I don't know about, is how was the NoFan tested here at SPCR: with the motherboard placed horizontally (and the NoFan vertically), or with the motherboard placed vertically (and the NoFan horizontal). Because looking at the heatpipes in the NoFan, I expect the performance on a vertical mounted motherboard to be worse, since the lower heatpipe that deserves the bottom half of the cooler has all its ends below the heat source (the CPU). I've seen on the frostytech site, in their heatsink reviews, that the NoFan also appears in the results table, but in two orientations: horizontal and vertical, and the difference in temperature between the two orientations is rather large. The only problem with the frostytech results table is that there is no explanation what is supposed to be horizontal - the motherboard or the heatsink. And I don't have the NoFan mounted on anything to test by myself anymore.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 5:34 am 
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i might have missed something, but

bbalex wrote:
and safe gaming when placing the window cover back over the top panel and letting that big front fan spin.


doesn't match with

bbalex wrote:
I'm not convinced of the ability of the Macho or HR-22 to safely keep the CPU cool, in fanless operation with no fan spinning, and only convection cooling.


So please make up your mind, because those two things are somwhow contradicting. Macho + case fan nearby has been proven to work. And a case fan spinning with the proper rpm is practically inaudible.


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 5:41 am 
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I probably have not worded this properly. There would be two modes of operation:
- when not gaming, the top window is removed, the front fan not spinning, all cooling done passively;
- when gaming, manually place the top window back first, and let the BIOS start the front fan when the CPU temperature gets above a certain threshold

To me, this seemed ideal, since I rarely do some gaming nowadays, but it still leaves that possibility open. :D


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 Post subject: Re: Mounting a CPU heatsink without the backplate
PostPosted: Sun Sep 14, 2014 3:25 pm 
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bbalex wrote:
I would like your advice on whether it's safe to mount a large (1Kg) CPU heatsink on a motherboard, but without mounting the heatsink backplate.
If the mobo's horizontal and the system is rarely and carefully moved, it probably won't cause damage, but increased mobo flexion might compromise mount quality. My mostly uneducated guess is that it wouldn't, but I'm a long ways from expert on that score.

Regardless, there's plenty of ways to mod the backplate so it fits, either by drilling it, as previously suggested, or by fiddling around with some sort of spacer(s).

bbalex wrote:
I'm not convinced of the ability of the Macho or HR-22 to safely keep the CPU cool, in fanless operation with no fan spinning, and only convection cooling. The test here on SPCR showed that the temperature just kept on raising, till the CPU finally throttled.
That test isn't really applicable here. There's a huge difference in heatsink effiency between a 100%-fanless system like the testbed and a nearly-fanless system like the one you're suggesting. Even if you plan on having no fans spinning under non-gaming conditions, the loads should be significantly lighter than in the test, and so long as some fan somewhere is moving a little air in the heatsink's direction, you'll see much better performance no matter the heatsink. My guess is that the HR02 or HR22 would be sufficient for you, and far easier to fit.

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