Do you need top & side Case fans?

[Gurd99]

My PC has two front 12cm fans, in the middle of this breezeway is my cpu cooler w/ 12cm fan & behind it is the rear fan. All fans spin under 1000rpm to be silent.

I want to know if I need top & side fans too? I think not as long as I add a small low rear fan to pull the warm air near the GPU out the back as that area is not in the breezeway.

In general are the top fans needed? wouldn't they weaken the effect of the single breeze from front to rear? I know hot air rises, but maybe this is only for OC systems in 33C ambient temps?

thanks

[johns0]

Depends where you live,if you need a lot fans due to hot weather then you need to have fans in the front and back and sides,as to top fans that's going a bit too much,i live in a moderate climate so i only have front and back fans.

[usually_quiet]

Today either the top or rear fan location is often used to install the radiator and fan for a liquid CPU cooler. That leaves the other locations available to use for the case exhaust fans.

[redwudz]

I've seen quite a few cases with side fans and directors to blow air into the CPU fan.
A really bad idea if they have no filters as you just blow dust directly into the CPU cooler and clog it.
I tape off those fan holes.

Top fans work well, but if you have a rear fan, kind of messes up the airflow. If they aren't used I would also plug them.

I like two intake fans to the front and two (If possible) exhaust fans to the rear of the case to achieve a straight through linear airflow.
I plug any other holes in the case that could leak air.

If your case and CPU temps are a bit high, remove one of your case side covers and re-check them.
If the temps drop a fair amount, you likely have a air circulation problem.
If the temps go up or stay about the same, you probably have a well designed air handling system.

I use HWiNFO to read case temperatures as I found it the most reliable. http://www.hwinfo.com/download.php

[pandy]

This can be tricky as fans can create areas with no flow (air flow may be in opposite direction).
Be careful - do some basic math and calculate flows - sometimes single fan can be better than many of them.
I also suggest to create pressure inside (fan pump air trough dust filter) - this fan should have more flow than sum of others.

[Gurd99]

I've seen quite a few cases with side fans and directors to blow air into the CPU fan.
A really bad idea if they have no filters as you just blow dust directly into the CPU cooler and clog it.
I tape off those fan holes.

Top fans work well, but if you have a rear fan, kind of messes up the airflow. If they aren't used I would also plug them.

I like two intake fans to the front and two (If possible) exhaust fans to the rear of the case to achieve a straight through linear airflow.
I plug any other holes in the case that could leak air.

If your case and CPU temps are a bit high, remove one of your case side covers and re-check them.
If the temps drop a fair amount, you likely have a air circulation problem.
If the temps go up or stay about the same, you probably have a well designed air handling system.

I use HWiNFO to read case temperatures as I found it the most reliable. http://www.hwinfo.com/download.php

Thanks, ill try removing one side of case & see.


Personally I don't believe in filters as it's more stuff to clean. I just blow out the parts like heat sink ever few weeks. Soon as the room temp gets to mid 30's C I turn the air con on.

[redwudz]

Filters do help. I have just a screen type filter on my main PC. I clean it once a month.
But once a year I take it mostly apart and clean my fans and the interior of my case as 'stuff' still accumulates.

My screen filter is similar to a piece of lady's panty hose and that can also be used instead of a regular screen to stop most of the dust from entering the case.

Dust itself isn't really the problem, It's cooking grease and other oils in the air that clogs up my system. The dust sticks to that. But my screen filters stop 75% or more.

I should also mention that the 'dust' in most PCs is pollen, lint, and human and animal skin cells and other nasty stuff. Blow it off outdoors or at least wear a particle mask;
You don't want to breathe it.

[pandy]

Personally I don't believe in filters as it's more stuff to clean. I just blow out the parts like heat sink ever few weeks. Soon as the room temp gets to mid 30's C I turn the air con on.

Well... people designing clean rooms believe in filters - general rule is: create overpressure in cabinet and prevent dust to enter inside - you can partially blow dust bust very fine still be present everywhere - it is common that optical drives are not working very quickly - dust is not only heat sink issue.
Filters can be replaceable - no need to clean. One large fan with CFM capability higher than sum of the all fans. Use air ducts to shape air flow - this is most efficient way of cooling - everything need to start and end somewhere - directing air flow will help a lot.

[TimA-C]

The simple answer is "It depends on your system." If you're happy with the temperatures reported by your motherboard and it's quiet enough for you then No, you probably don't need any additional fans. If you're not happy with the temps you're getting then you have to identify what's running hotter than you would like and come up with a solution. That might be an additional fan or two, it might be switching to liquid cooling, it might be changing the position of a PCI/PCI-E card or a hard drive or even just tidying up cables to improve the airflow inside the case. It could be changing an existing fan, or speeding up or slowing down one or more existing fans, adding or changing heatsinks, replacing the thermal paste under a heatsink, or even modifying or replacing the case. It just depends on each system, what it's being used for and, of course, what is acceptable in terms of temperature, noise and cost to the owner.

The current processors generate a lot less heat than their earlier counterparts, so I'd argue that this much less of an issue than it was, say, ten or fifteen years ago.

[Gurd99]

Thanks all.

I removed my side case door & within 30mins the average temps on GPU, CPU & HDD went down by almost 3degrees C. I think because the fans spin slowly just under 1000rpm the airflow is weak & not getting that cooler outside air.

In regards to dust & static caused by vacuum cleaner, does anyone know if its safe to vacuum when machine is turned off? Or if it's still a risk like when on? Secondly, if static is caused by the vacuum sucking, why not a blower? Still air rushing through the nozzle.

[redwudz]

I haven't used a vacuum in quite a while for PC cleaning as they don't really get all the dust out and there is a chance you can cause some damage with the nozzle. I use 'canned air' or sometimes my air compressor to carefully blow out the dust, along with a soft brush to loosen it around the heat sinks.

Static isn't a huge problem with a PC as everything should be grounded and protected against most static. But you can leave the PC plugged in and off if you are worried about ungrounded components.

I pull both side covers off and blow off the dust outdoors while wearing a particle mask.

I also block all fans with a zip tie to keep them from over speeding and damaging the bearings while I blow out dust. And I wouldn't blow air into the optical drives as you can force the dust deeper and cause future problems. After I blow out the dust, I follow up with a lint free towel dampened with a bit of window spray to clean all the large internal surfaces.

When you check case temperatures you want to have the PC running at 100% to get a good reading. I do that by encoding MKVs. A three degree C drop in case temps isn't too serious with the side covers off. But you might look at your fans and see if you can install some more efficient, but still quiet models.

Dust problems? I found this photo from a member a few years ago.

[Gurd99]

I haven't used a vacuum in quite a while for PC cleaning as they don't really get all the dust out and there is a chance you can cause some damage with the nozzle. I use 'canned air' or sometimes my air compressor to carefully blow out the dust, along with a soft brush to loosen it around the heat sinks.

Static isn't a huge problem with a PC as everything should be grounded and protected against most static. But you can leave the PC plugged in and off if you are worried about ungrounded components.

I pull both side covers off and blow off the dust outdoors while wearing a particle mask. You don't want to breath that dust. (Mostly lint, pet dander, pollen, skins cells and other nasty stuff.

I also block all fans with a zip tie to keep them from over speeding and damaging the bearings while I blow out dust. And I wouldn't blow air into the optical drives as you can force the dust deeper and cause future problems. After I blow out the dust, I follow up with a lint free towel dampened with a bit of window spray to clean all the large internal surfaces.

When you check case temperatures you want to have the PC running at 100% to get a good reading. I do that by encoding MKVs. A three degree C drop in case temps isn't too serious with the side covers off. But you might look at your fans and see if you can install some more efficient, but still quiet models.

Dust problems? I found this photo from a member a few years ago.

Thanks, I'm eyeing the datavac blower, a 220V model anyway. Up until now I have used my breath to blow it all out & clean fan blades with cloths.

[pandy]

Use firm brush and vacuum cleaner - ES is dangerous but i bet you will not build sufficient ES field (depends on air humidity) - if you afraid ES use fabric softener as crude ESD protection - make softener water solution with twice three times more softener than usually used for laundry - spry with such solution area where you work and vacuum cleaner tube (outside and if possible as much you can inside) - allow to dry.

[glenpinn]

sometimes single fan can be better than many of them.

yes, there is absolutely no need for any more than 1 single 12cm extractor fan in the centre, or near the top of the rear panel of the case, regardless of the outside air temp.

The principal to efficient pc case cooling is to have a steady flow of cool air flowing over the motherboard from the front of the case to the rear, and have that line of air pass over the CPU area.

Aftermarket CPU Coolers are also not required in many cases if you have efficient cool air flowing correctly thru your case.

LOL at using a vacuum cleaner to remove dust from inside the case, just asking for trouble with this rediculous habit.

Use a blower to blow, do not use a vacuum to suck.

Having multiple fans blowing air into a case is absolutely pointless, all it does is creates turbulence and builds up pressure inside the case, and this can actually be worse than having no fans in the case at all.

To all my wonderful Fans, i rest my Case

[PuzZLeR]

Regardless of where you live, or how cold/hot your place is, what type of case/fan structure you have, dust is dust and is the biggest issue. Just buy a bottle of compressed air, and once a month open up the case and give it a good blast. And you should notice, particularly on the older PCs, a performance boost if your computer needed it - faster encode times, smaller or zero buffers, etc..

Vaccuum cleaners, blowdriers, and brushes - forget about it.

Use a blower to blow, do not use a vacuum to suck.

I'm still trying to decide whether this thread sucks or blows.

[glenpinn]

and give it a good blast. And you should notice, particularly on the older PCs, a performance boost if your computer needed it - faster encode times, smaller or zero buffers, etc..

So i don't need a fast CPU for encoding, just blow off the dust and my encode times will be faster, and have better performance, wow i had no idea that this was all i needed to do on my old computer, could have saved me a lot of money

Seriously, faster encode times by removing some dust ????

[usually_quiet]

and give it a good blast. And you should notice, particularly on the older PCs, a performance boost if your computer needed it - faster encode times, smaller or zero buffers, etc..

So i don't need a fast CPU for encoding, just blow off the dust and my encode times will be faster, and have better performance, wow i had no idea that this was all i needed to do on my old computer, could have saved me a lot of money

Seriously, faster encode times by removing some dust ????

If the inside of a PC is looking more like the inside of a vacuum cleaner bag than a computer and the CPU is consequently throttling to protect itself from over-heating, then yes, I can see a possibility of better performance after a good cleaning.

[PuzZLeR]

and give it a good blast. And you should notice, particularly on the older PCs, a performance boost if your computer needed it - faster encode times, smaller or zero buffers, etc..

So i don't need a fast CPU for encoding, just blow off the dust and my encode times will be faster, and have better performance, wow i had no idea that this was all i needed to do on my old computer, could have saved me a lot of money

Seriously, faster encode times by removing some dust ????

Yes, and not because Usually Quiet backed me up. I know it sounds crazy, and wouldn't have believed it myself until I saw it live and happening to me. Your computer slows down on purpose, particularly certain generations of Intel processors, to prevent being a fire hazard.

This is true.

And yes, when the dust is cleared, your processor will get the the go-ahead to run at higher speeds, hence faster encodes, little-to-zero buffers on captures, etc., and I did say particularly more so if your computer really needed it.

Also, emphasizing on captures only, still relevant with the topic here if you check #4 here for more info on this. They talk about overheating, but dust too can cause overheating.

http://www.digitalfaq.com/guides/video/capture-dropped-frames.htm

So, the Moral of the Story Boys and Girls - Keep your PC clean!

[redwudz]

On my main PC, the one in my computer details, I clean the intake filters once a month with mild soap and water rinse.

The insides of the computer about twice a year. I remove the fan blades and clean them and also blow out all dust and wipe down the inside of the case with a mostly lint free makeup removal pad and Windex or similar to pick up dust.

I also check where the dust is coming in from and plug all open holes that seem to be admitting dust. Just switching to liquid CPU cooling has helped most of my cooling and dust problems.

I normally run temperature checking programs once a month like HWInfo to get an accurate rating of any changes to the cooling performance.
My PC uses a 125W CPU and it runs about 47C under 100% load on all cores, so I'm happy with that.

[glenpinn]

I'm still trying to decide whether this thread sucks or blows.

LOL, well i think it just might be both based on some of the stuff that is being said by you in here (and a few of the other computer based threads i have seen as well) so rather than get caught up in any argumentative and endless debates about over heating CPU's and what really happens when they do get hot, i am just going to let you carry on with what you have to say, just knowing that most of what you are saying i believe is wrong, and i won't be responding to any more comments that you have to make about anything i have to say either, because i doubt that you are ever going to listen anyway.

Cheers

[PuzZLeR]

I'm still trying to decide whether this thread sucks or blows.

LOL, well i think it just might be both based on some of the stuff that is being said by you in here (and a few of the other computer based threads i have seen as well) so rather than get caught up in any argumentative and endless debates about over heating CPU's and what really happens when they do get hot, i am just going to let you carry on with what you have to say, just knowing that most of what you are saying i believe is wrong, and i won't be responding to any more comments that you have to make about anything i have to say either, because i doubt that you are ever going to listen anyway.

Cheers

I get it. It sucks to be proven wrong as was clearly demonstrated here. And your reaction is predictable.

Cheers to you as well.

[glenpinn]

I get it. It sucks to be proven wrong as was clearly demonstrated here. And your reaction is predictable.

LOL you proved nothing, just because one other person kind of agreed with one thing you said does not mean that you proved me wrong, jesus man, he could have been wrong himself.

The problem with forums is they are full of sheep, and sheep are the dumbest animals in the world, they all gather in a flock in the paddock, then one begins to walk away, then all the others line up behind it and follows it, no mater where it goes, they all go with it, so if the first sheep falls off a cliff, all the others follow, just like some members here in this forum.

2 people agreeing with one another does not mean you are right.

And as for this link, well that just about sums it all up for me, along with all the other dribble being said in all those other links being posted, none of it means jack shit, and you believe all of it ??????

http://www.digitalfaq.com/guides/video/capture-dropped-frames.htm

[PuzZLeR]

I get it. It sucks to be proven wrong as was clearly demonstrated here. And your reaction is predictable.

LOL you proved nothing, just because one other person kind of agreed with one thing you said does not mean that you proved me wrong, jesus man, he could have been wrong himself.

Intel processors had, and likely still have, a built in mechanism to slow down when sensing heat - since the dawn of this century, or earlier. This is fact. It was criticised at first, but accepted later when it was to prevent fire hazards or melting motherboards.

So when there is dust in the machine, this clogs ventilation and increases heat. You don't need a physics degree to understand this. This is when the processor slows down. Clearing this dust sends a cooler signal to the processor. If you had a lot of dust there, and removed it, this would boost performance. This is fact. And temperature control is not uncommon - it resides in thermostats, automobiles, and other technology. This too is fact.

The problem with forums is they are full of sheep, and sheep are the dumbest animals in the world, they all gather in a flock in the paddock, then one begins to walk away, then all the others line up behind it and follows it, no mater where it goes, they all go with it, so if the first sheep falls off a cliff, all the others follow, just like some members here in this forum.

This is what I described in another thread of Doom9. Sheep. They post to please the bias of the Moderators, and keep their prose in place to avoid "strikes".

However, this is not that type of Forum. Thanks to the Mods on this one.

2 people agreeing with one another does not mean you are right.

True. And I did state that the backup, with Usually Quiet, was irrelevant, although appreciated. However, I wouldn't be surprised if 10, or even 100, people started agreeing with me on this one.

And as for this link, well that just about sums it all up for me, along with all the other dribble being said in all those other links being posted, none of it means jack shit, and you believe all of it ??????

http://www.digitalfaq.com/guides/video/capture-dropped-frames.htm

True. DigitalFAQ would be a great forum if half of the stuff they say there isn't wrong. But I do believe in what was said there about overheating and capturing. This is because - HONESTLY - I've seen this myself with my own computers.

[hello_hello]

Intel processors had, and likely still have, a built in mechanism to slow down when sensing heat - since the dawn of this century, or earlier. This is fact. It was criticised at first, but accepted later when it was to prevent fire hazards or melting motherboards.

So when there is dust in the machine, this clogs ventilation and increases heat. You don't need a physics degree to understand this. This is when the processor slows down. Clearing this dust sends a cooler signal to the processor. If you had a lot of dust there, and removed it, this would boost performance. This is fact.

I'll have to climb on the "sceptical" bandwagon for that one. I don't know how every Intel CPU works, but I don't think the principle has changed since my old quad core was released. The CPUs have a maximum Tjunction temperature at which point they start to throttle themselves. I'm not sure if it's core temperature as such, but it's described as junction temperature (or TJ Max) and it's the temperature at which the CPUs start to throttle. It's very high. Usually somewhere around 100 degrees Celsius, and if a CPU is adequately cooled the Tjunction temperature shouldn't be any more than 10 degrees higher than TCase, temperature, which means if you're just monitoring "CPU temperature" the maximum before throttling is often around 90 degrees. There's some sort of unofficial temperature list here: https://www.kernel.org/doc/Documentation/hwmon/coretemp

I'm not saying the slowdown thing can't happen, just that most Intel CPUs need to get very hot. My old E6750 is slightly overclocked and running on the stock cooler and when it's running flat out on a very hot summer day it can get hot enough to set off the BIOS temperature alarm, which I think I'd set to 80 degrees, but I've not noticed it slowing down. It's not in a case with a large amount of airflow so heat can build up inside too much on hot days. Intel CPUs really do have to get quite hot to throttle though.

The current state of my old Q9450. CPU usage is sitting on 50% running a single threaded QTGMC encode, although it doesn't get all that much hotter running at 100% as the CPU fan speed increases accordingly and I'm using a larger cooler than the stock one. Still, at the moment I've got at least 45 degrees of headroom before the CPU would start to throttle.



Plenty of times I cleaned out inches of dust covering heatsinks etc and told myself off for letting so much of it build up, as after it's removed the CPU temperature drops a little which means the fan speeds drop a little and the computer makes a bit less noise, but an increase in processing speed.... I've not see that yet.

[PuzZLeR]

Intel processors had, and likely still have, a built in mechanism to slow down when sensing heat - since the dawn of this century, or earlier. This is fact. It was criticised at first, but accepted later when it was to prevent fire hazards or melting motherboards.

So when there is dust in the machine, this clogs ventilation and increases heat. You don't need a physics degree to understand this. This is when the processor slows down. Clearing this dust sends a cooler signal to the processor. If you had a lot of dust there, and removed it, this would boost performance. This is fact.

I'll have to climb on the "sceptical" bandwagon for that one. I don't know how every Intel CPU works, but I don't think the principle has changed since my old quad core was released. The CPUs have a maximum Tjunction temperature at which point they start to throttle themselves. I'm not sure if it's core temperature as such, but it's described as junction temperature (or TJ Max) and it's the temperature at which the CPUs start to throttle. It's very high. Usually somewhere around 100 degrees Celsius, and if a CPU is adequately cooled the Tjunction temperature shouldn't be any more than 10 degrees higher than TCase, temperature, which means if you're just monitoring "CPU temperature" the maximum before throttling is often around 90 degrees. There's some sort of unofficial temperature list here: https://www.kernel.org/doc/Documentation/hwmon/coretemp

I'm not saying the slowdown thing can't happen, just that most Intel CPUs need to get very hot. My old E6750 is slightly overclocked and running on the stock cooler and when it's running flat out on a very hot summer day it can get hot enough to set off the BIOS temperature alarm, which I think I'd set to 80 degrees, but I've not noticed it slowing down. It's not in a case with a large amount of airflow so heat can build up inside too much on hot days. Intel CPUs really do have to get quite hot to throttle though.

The current state of my old Q9450. CPU usage is sitting on 50% running a single threaded QTGMC encode, although it doesn't get all that much hotter running at 100% as the CPU fan speed increases accordingly. Still, at the moment I've got at least 45 degrees of headroom before the CPU would start to throttle.


[Attachment 34627 - Click to enlarge]

Plenty of times I cleaned out inches of dust covering heatsinks etc and told myself off for letting so much of it build up, as after it's removed the CPU temperature drops a little which means the fan speeds drop a little and the computer makes a bit less noise, but an increase in processing speed.... I've not see that yet.

I don't have the facts on which generation of Intel, and don't really care. And your whole post did indeed say that processors do indeed fluxuate in performance as a function of temperature. That was my whole point.

As to how much, or when or what, I never said that it does all the time. But certain generations of Intel processors, if not the majority, do indeed slow down when the levels reach what they deem is a serious threshold. That means that if you built lots of dust there, and/or your fan or cooling system is failing, you will notice a drop in performance. That's because your PC is hot past the limits acceptable. It's applying a form of damage control.

I didn't say it slows down at all levels. I did mention, now for the third time, with the applicable processor, you will notice this speed increase if your PC needed that cleaning or cooling, whereas just previously it was full of dust and/or had failing parts.

My experience was from a mid 2000s duo core Intel that had this problem. When I changed the fan, sink, and cleaned it out, it ran much faster, closer to the levels it ran when it was brand new. The improvement couldn't have been more noticeable.

[hello_hello]

Dust won't completely block air flow, just slow it down, and CPUs keep running at the same speed up to a certain temperature. You described it as reaching "a serious threshold" yourself, which means "extremely hot", and that'd take a lot of dust, especially in an otherwise well ventilated case. It'd normally take a combination of lots of dust where cooling is only "adequate", the CPU is working really hard and the ambient temperature is quite high, and even then I suspect "lots of dust" would only play a minor role. As it probably did in your example, otherwise you could've cleaned out the dust and continued to use the original fan and heatsink.

Maybe the CPU was throttling due to excessive temperature because the old heatsink wasn't seated properly or due to poor thermal compound etc and that was rectified when you upgraded the cooler, and maybe in that sort of scenario excessive dust even helped push temperatures over the limit, but when it comes to dust being the cause of CPU throttling as a general rule, I'm sceptical.

[usually_quiet]

I have seen horrible dust accumulation in a PC owned by relatives, and by that I mean worse than what is shown in Redwudz's photo. The PC in question was near a cage housing a pet c*o*c*k*atiel, which generated an amazing amount fine debris for one small bird.

It was bad enough that I would not have been surprised if there were some heat issues, but I wasn't looking for them. I had opened the case up to install a hard drive. I needed to take the PC outside and clean it so I could do the work. I told the owners to check for dust now and then although I don't think that was ever done. This same PC did actually catch on fire at a later date. When I asked about dust inside the PC the answer was "I don't know".

[PuzZLeR]

Dust won't completely block air flow, just slow it down, and CPUs keep running at the same speed up to a certain temperature. You described it as reaching "a serious threshold" yourself, which means "extremely hot", and that'd take a lot of dust, especially in an otherwise well ventilated case. It'd normally take a combination of lots of dust where cooling is only "adequate", the CPU is working really hard and the ambient temperature is quite high, and even then I suspect "lots of dust" would only play a minor role. As it probably did in your example, otherwise you could've cleaned out the dust and continued to use the original fan and heatsink.

Maybe the CPU was throttling due to excessive temperature because the old heatsink wasn't seated properly or due to poor thermal compound etc and that was rectified when you upgraded the cooler, and maybe in that sort of scenario excessive dust even helped push temperatures over the limit, but when it comes to dust being the cause of CPU throttling as a general rule, I'm sceptical.

Fair enough. I can't say which was the real culprit, but there certainly was dust in the unit, and the fact that I did both - clear the dust and change the cooling system - doesn't say which has caused the performance boost if it was only one of them.

But there definitely was a performance boost which was more than noticeable, so for sure it has to do with cooling and/or cleaning dust. I can't say this was coincidence otherwise.

However, doesn't lots of dust clog ventilation in the unit? It makes sense to me that this lack of proper air flow would increase the heat in the machine.

[PuzZLeR]

I have seen horrible dust accumulation in a PC owned by relatives, and by that I mean worse than what is shown in Redwudz's photo. The PC in question was near a cage housing a pet c*o*c*k*atiel, which generated an amazing amount fine debris for one small bird.

You're making me think and wonder if it was my cats creating that "debris" in my machine that time from my experience mentioned about a machine having a performance boost after cleaning and upgrading the cooling.

I've been habitually blasting my machines with compressed air since, so I'm now wondering if what would pile up in there otherwise would indeed be cat residual, and not just "ordinary dust".

[hello_hello]

However, doesn't lots of dust clog ventilation in the unit? It makes sense to me that this lack of proper air flow would increase the heat in the machine.

No doubt if dust reduces airflow it'd increase temperatures to some extent. And depending on the cooling and ambient temperature etc enough of it could lead to excessive temperature issues.
I think the worst I've seen was a PC running a lightshow in a nightclub. I remember opening it up and it looked more like the inside of a vacuum cleaner bag than a PC.

You're making me think and wonder if it was my cats creating that "debris" in my machine that time from my experience mentioned about a machine having a performance boost after cleaning and upgrading the cooling.

We've managed to accumulate a few cats here, but I don't recall removing much cat hair from inside a PC, despite the fact it seems to get into everything else. I think it's heavy enough not to get "sucked in" by fans the way dust does. None of the PCs here have dust filters but if dust accumulates over a vent enough to form it's own dust filter it also doubles as a filter for cat hair too.