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Question Case fan 'clusters' - CPU & GPU dependant. Good idea?

Ralfi

Junior Member
Aug 26, 2021
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0
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Hey there.

Wondering if it's a good idea to have some fans be governed by CPU temp & others by GPU temp?

Specifically, in my below example, where I have 3 x front intake fans, 1 x CPU HSF, 1 x Rear exhaust fan & 1 x Top exhaust fan...

1629973101084.jpeg

Let's say I was thinking of hooking up my fans above in the following way;

Green arrows = CPU Temp controlled fans. Ie. Front to back.
Orange arrows = GPU Temp controlled fans. Ie Bottom to Top.

This is merely a hypothetical thing, as my current fan curves are working well (& quiet), but i'm just curious on whether this theory may improve things?

Thanks.
 

sdifox

No Lifer
Sep 30, 2005
86,099
9,944
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Waste of time, you just want to constantly cycle out all the air in the case. Lots of stuff (like nvme) depends on airflow to cool.
 
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CU

Platinum Member
Aug 14, 2000
2,335
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I wouldn't have some fans controlled by the temp of one component and some by another. I would have all the fans controlled by the system temp, or if you can, control them by cpu, gpu, etc. temps so that if anything gets "hot" all the case fans will ramp up.
 
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mindless1

Diamond Member
Aug 11, 2001
6,486
833
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In theory what you propose makes sense and could achieve temperature targets that change less, but the real world benefit of this is fleeting.

Since you are already achieving acceptable temperatures and low noise, it would reduce the frequency of cleaning dust out of the system (or ideally some intake filters), and extend the lifespan of the fans, but if using decent fans they should already provide good enough service life, and you already have enough of them that if any single fan were to die, the system should still be fully usable until you get a chance to replace it, except possibly the CPU 'sink (depending on what CPU it is and/or whether overclocked), so I always want the CPU 'sink to vary RPM based on CPU temp to extend its lifespan.
 
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BoomerD

No Lifer
Feb 26, 2006
57,801
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Not to mention...if both cpu and gpu get hot enough to trigger the fan cycle, you'd lose a lot of the targeted airflow to turbulence...potentially disrupting the cooling for one or the other...or both.
 
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Ralfi

Junior Member
Aug 26, 2021
11
0
11
Appreciate all the replies.

Main thing that sparked this idea was that for most uses, the CPU doesn’t really get hot (idles at 33° with rare spikes up to 40°), & with games, it stays below 65° (Only gets hotter when stress testing, as per screen below). GPU idles at 34/35 (Edge/Hot spot) & at load is 72°/81°.

Benching both CPU & GPU, the current fan setup handles things fine (see below), but my curiosity always has me thinking outside the box 😁.
0A5FD106-4C75-4F0F-9B0C-AE3D7A71A3CA.png

Just to confirm, if the Top exhaust fan was switched to also be dependent on CPU temp, would that be better? That would just mean the 2 lower front fans would ramp up to provide fresh air for the GPU to suck up.
 

mindless1

Diamond Member
Aug 11, 2001
6,486
833
126
^ You don't really need the top fan at all (just to block any passive holes in the top of the case), so do whatever you want with it. Personally I prefer no top fan so I can put things on the entire top of the case, though an exhaust fan there would come in handy to put a ball cap on to dry it out after I've been sweating outdoors. :)
 

Paperdoc

Platinum Member
Aug 17, 2006
2,041
168
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Consider from this point of view. All of these fans are actually under the control of loops that concentrate on the measured TEMPERATURE at specific sensors in the system. Further, they all assume that the general CASE vent fans will do their thing guided by the temperature measured by a sensor on the MOBO, and that establishes the temp of the air available for use to cool the CPU and GPU chips. So those latter two systems do NOT expect to have outside air as their source. The CPU cooler (especially the type you have, a fan and heatsink on the CPU chip) uses a temp sensor inside the CPU chip and adjusts is fan speed to keep that where it is supposed to be. NOTE that, if you were to provide cooler air to that fan for this purpose, the fan control system would simply find that the CPU is running cooler than planned, and slow the fan down a bit to keep the CPU temp on target - it may NOT actually decrease the CPU internal temp! Similarly, for the GPU chip, it has its own control system based on the real GPU internal temp, and using the normal case interior air.

There is another factor - the availability of data. Usually the CPU_FAN header will ONLY allow the use of the sensor inside the CPU chip. SYS_FAN or CHA_FAN headers on the mobo normally are set to use the mobo sensor - actually, a sensor in a spot the mobo maker judges the most important for cooling of all major mobo heat sources. Often there is an option for some of these headers to use other sensors instead - either the one inside the CPU, or others on specific mobo components. These are really suitable for use IF you are creating a special cooling loop for a particular component by dedicating (by aiming) a fan at that item, and the using its own sensor to guide that one fan. But using the CPU temp to guide mobo cooling generally is not so good.

The GPU fan is a very different matter normally. There has never been a standard means of sending the temp measurement inside the GPU chip out to the mobo, so NO system has the MOBO controlling cooling of the GPU chip. Instead, the video card itself has its own fan control system guided by that GPU internal sensor, and expecting to use general case air. So normally you can NOT control GPU cooling using a mobo fan header, and you cannot feed any mobo or CPU temp sensor info into the video card to guide its fans. In almost all cases you will find that control and configuration of GPU chip cooling is done using utilities supplied by the video card maker that communicate with that card, and not with the mobo.

If you really believe that you need your mobo or CPU temps to run lower, on most mobos you have the option to set your own version of a "fan curve" for each header. That is the settings of what fan speed to run for a given temp measurement. You can set it to run faster at all temps and force it to run your components cooler under most conditions. There may be a limit that, at max workload and heat generation, you find the fans already have been set to run full speed at a lower temp and you've reached the fan cooling limit, but that is not usually a big concern. Doing this will cause marginally faster fan wear. Whether or not it also results in longer lifetime for the units you over-cool this way is very hard to say.
 
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