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faster system fan blowing in CPU=less temps, NOT!

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March 3, 2005 8:07:58 PM

I had a regular 2800 rpm case fan blowing on my CPU to help with keeping the temps down. So I thought hey lets put in a thermaltake smartfan 2 that is currently running at
5110 RPM. Guess how much it lowered my cpu temps, one degree. Well Now i have a faster and noiser case fan but not much of a cooler cpu. Maybe I'll put a funel on and see if that helps.

<P ID="edit"><FONT SIZE=-1><EM>Edited by newdude on 03/03/05 05:09 PM.</EM></FONT></P>
March 3, 2005 8:50:59 PM

Well it lowered the temps about 2 degrees. I think my cpu just running cool as it's going to get without actually blowing colder air on it.
Right now it's 29 degrees. And the cpu fan and heatsink is a 60 mm fan, were the case fan is 80mm. the case fan runs much faster that the case fan, I guess I need to have a cpu fan that runs at the same speed to suck in as much air on the cpu as the case fan is blowing in.
<P ID="edit"><FONT SIZE=-1><EM>Edited by newdude on 03/03/05 05:55 PM.</EM></FONT></P>
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March 3, 2005 9:22:16 PM

The HSF is moving hot air away from the CPU - not onto it. You could try making the rear case fan your intake fan and the front fan your exhaust fan. That way your intaking cool air and blowing it right into the area of the CPU.

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March 3, 2005 9:27:27 PM

Hold up, Now i'm completely confused. ISn't the cpu fan blowing air on the CPU chip not sucking air out. I mean whenever you see a case fan on the side isn't it blowing air on the cpu area. Isn't the object to get cooler air to blow on the cpu to cool it off.

<P ID="edit"><FONT SIZE=-1><EM>Edited by newdude on 03/03/05 06:30 PM.</EM></FONT></P>
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March 3, 2005 9:39:40 PM

HSF: The heat sink draws heat from the CPU and then dissipates that heat into the air. The reason you have fins is to make more surface area for the heat sink to pass the heat into the air. The fan on the heat sink then draws the hot air away from the heat sink.
Case Fans: Purpose is to create an air flow by intaking cool air with one fan and exhausting air with the other fan.

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March 3, 2005 9:54:59 PM

very good answer dude, but also know that 1 or 2 degrees drop is a pretty good performance boost. also, we don't know what cpu you have or what kidn of ventilation you use so, we can't really help you that much if you don't provide these info. on a side note, if the fan that is on top of the heat sink has a very big center, then it is not effectively pulling air away because there is a dead spot in the middle of the fan. just remember rpms don't mean everything.

<font color=red>One Lowe</font color=red>
March 3, 2005 9:58:08 PM

What do you mean by having fins, could you expalin more?? Is this the blades on the fan?? Is the cpu fan blowing air on the cpu or sucking air of. I have a side case fan blowing air onto the cpu and a fan on the back sucking air out. I also have a case fan blowing air on the video card, and a fan sucking air in on the front bottom of my case. sorry, I have a athlon 64 3000 socket 754 newcastle design.

<P ID="edit"><FONT SIZE=-1><EM>Edited by newdude on 03/03/05 07:01 PM.</EM></FONT></P>
March 3, 2005 10:07:50 PM

and the cpu heatsink and fan is the one that came with the cpu retail. Don't want to change the cpu fan or heatsink because it'll void the warinty. Besides I'm not concerened about the temp geting hot the temps of my cpu right now is 28 degrees. Just i like to see how cool i can get my cpu with the least amount of cost. couple of weeks ago I just a box fan in the window and turned the fan on high and aimed it at my case. within a minute I had the temps down to 18 degrees. probally could have got it down more if it stayed longer. I even thought about building/ or gettin a case that i can put a small box fan on the side. I have a box fan in my house and it's quiter than my case fan. I'm going to put a funnel on the case fan blowing to the cpu and see what that does. I'll also trying switching the direction the fans blow on my rear fan and side cpu case fan.

<P ID="edit"><FONT SIZE=-1><EM>Edited by newdude on 03/03/05 07:10 PM.</EM></FONT></P>
March 3, 2005 10:13:52 PM

so in theory if i put a bigger cpu fan on the heatsink it will displace more air for the heat from the cpu to draw away from.
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March 3, 2005 10:14:24 PM

Tell us exactly how many fans you have, location, size (80MM, 90MM, etc) how many CFM (cubic feet per minute) they move and what direction they are blowing - into the case or out of the case. To test the direction your HSF is blowing you can use your hand, piece of paper or the feather you use to tickle your girlfriend. :evil: 

HSF = heatsink and fan. Heat sink touches CPU and a fan sits on top of the heat sink. The fan that is on the heat sink should move air <b>away</b> from the heat sink and CPU. The fins that I'm talking about are the metal ridges or blades of the heat sink - <b>not</b> the fan blades.

"newcastle design" Newcastle is the name of the CPU core.

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March 3, 2005 10:15:44 PM

well, this again shows that rpms arn't everything. case fans arn't designed to keep your cpu cool, it is designed to keep your case cool(the inside...duh). so to maximize this effect, i would suggest 2 intake and 2 exhaust. other then that, tie down your wires or try to get rounded wires to allow for more airflow. doing these things will keep the temps down a lil, but don't expect it to cool your cpu that much.

<font color=red>One Lowe</font color=red>
March 3, 2005 10:21:39 PM

I have a 80 mm intake fan on the bottom front of my fan, not sure what CFM is but it's a basic 2 dollar case fan from ebay. I have a 80mm regular case fan blowing air on my video card. And a thermaltake smart fan 2 case fan blowing air on my cpu. I have one exsust fan on the back of my case blowing air out and My thermal take powersupply fan with adjustable speed sucking air out of my case to. I'm thinking about putting a case fan on the top of my case to suck air out because i've noticed that heat seems to hibernate to the top were all the wires are and stuff.
March 3, 2005 10:25:32 PM

my suggestions for lower temps:

-use the 2 intake, 2 exhaust formation.
-GET BETTER FANS(more air flow, pressure)
-you have a case fan on your cpu? get ride of it and get a regular hsf, i suggest the zalman 7000 or 7700 copper
-tie down wires or get round cables

if you follow those guidelines, you should be fine

<font color=red>One Lowe</font color=red>
March 3, 2005 11:21:51 PM

CAN i get a new heatsink and keep the same fan, just for money issues. Or would it be best to change both. I'm on a limited budget so price can be a issue.
March 3, 2005 11:43:05 PM

okay one more quick question. If the object of the cpu fan is to push away hot air away from the cpu so theres no build up of hot air over the cpu then how does your case temperture also determine the cpu temps if none of the case air is getting to the cpu due to the fact that the cpu fan is pushing air away from the cpu. Why then when i put my box fan in the window and aimed it at my computer case and turned it on high did my cpu temps go down so low on my cpu. I just want to make sure I understand this correctly. I'm not trying to be sarcastic I just want to understand the idea of cooling. I would also like to see how the air flows in my case can you use like smoke or something so you can visualy see how the air moves in my case.

<P ID="edit"><FONT SIZE=-1><EM>Edited by newdude on 03/03/05 08:47 PM.</EM></FONT></P>
March 3, 2005 11:54:26 PM

the cpu has a pin for temp dude.... and the fan question isn't very legit... what if i asked you, why does my comptuer run cooler when i dip it in liquid nitro? and blowing smoke onto your system is

a)not smart
b)will fill up the room in smoke in a matter of minutes
c)the smoke will only give you info(if any at all) the first few seconds of activation because you can see a contrast in the air and the smoke

so don't do it =]

<font color=red>One Lowe</font color=red>
March 4, 2005 12:04:34 AM

then theres really no way of telling how the air flows in the case. Another thing is okay if the object of the cpu fan is to puch the hot air away, how about putting an extra fan on the side of the CPU to help push air away from the cpu and toward the rear fan to blow the hot air out.
March 4, 2005 12:12:53 AM

you kinda know how the air flows in the first place - air comes in the front and exits in the back =D. the fan above the HSF will help, but it depends on what HSF you have, if it is centrifugal, the it wouldn't help, but if it pulls air up like normal HSFs then sure, go ahead and try.

<font color=red>One Lowe</font color=red>
March 4, 2005 12:22:03 AM

okay first of all what is centrifugal. second would a regular case fan attached to the side of the cpu help displace air. should it be on the right side of the cpu blowing air away or should it be on the left side sucking air away??
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March 4, 2005 12:48:13 AM

Let's get back to basics before we, the collective braintrust of the THG forums have you buying and moving fans from here until teh cows come home. What is your case temp and what is your CPU temp at full load?

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March 4, 2005 12:56:24 AM

Quote:
temps of my cpu right now is 28 degrees.

Reality check. What is this whole thread doing. Are you going to try to get a modern chip to power up a chilling unit? There are physical laws that apply here. The chips going to put out heat. That heat can only be displaced so fast, esp with air cooling. There are people out there who would like those numbers, who are using liquid cooling.
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March 4, 2005 1:05:31 AM

To be honest I think it's more likely that 29C is the case temp and he has a load CPU temp around 50C. =/ He just needs to confirm that to us and we can be done with this thread. :smile:

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March 4, 2005 2:31:02 AM

The funnel will probably help if you design it properly. I agree that you probably do have circulation issues.

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March 4, 2005 2:34:52 AM

You are the first person here other than myself that I have seen suggest reversing the rear fan. Its the first thing that I do when I am building a new system. Especially when you have a 120mm fan on the front and back of the case it can really make a difference. I dont know why this isnt talked about more than it is.

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March 4, 2005 2:47:58 AM

:redface: I actually got the idea from you. Great idea! Actually did it on my current system and got a 1.5C drop in temp.

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March 4, 2005 3:14:58 AM

wait, am i missing a crucial trick here, "reversing" the rear fan? so the air flow goes from the back to the front? how does that help

<font color=red>One Lowe</font color=red>
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March 4, 2005 6:55:45 AM

The rear exhaust fan is closer to the cpu and blows cool air directly onto the cpu and hsf... but wait a minute, if warm air rises to the top of the case and cool air settles down, wouldn't reversing the air flow actually recirculate the hot air from the hsf in the case longer? But if that's true, then how did you both get those results??? ARGH!!! :smile:

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March 4, 2005 7:24:39 AM

That's easy, the airflow exhausts mostly through the psu.
The best is when you intake at back and front, and use the psu, and a top blowhole for exhaust.
March 4, 2005 10:00:18 AM

oKAY MY cpu temp is 31 degrees right now. I know it's my cpu temp and not my case temp because I have a gabyte GA-k8NS amd It has an onboard thermal sensor and shows the temps of my cpu on my EAsytunes4. I have no idea what my case temps, don't have a thermometer for that yet. now A thank my temps on my cpu are fine, heck they're wonderfull. Just for fun I would like to see how much cooler I could get it. I'm gratefull for everyones input. Just trying to see how cool i can get it.
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March 4, 2005 1:24:59 PM

Try getting MBM5. It will allow you to read both the case and CPU temps, as well as a lot of other great things like fan speeds, voltages, etc. If you really do have a 31C CPU then you are Golden - is that at idle? Is cool & quiet active? What are the temps under full load (running Sandra or a 3D Mark)? The load temps are the ones you really need to worry about.
Quote:
Endyen: That's easy, the airflow exhausts mostly through the psu. The best is when you intake at back and front, and use the psu, and a top blowhole for exhaust.

If he doesn't have a top blowhole, then intake at the fron and rear - exhaust at the side fan and the PSU.

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March 4, 2005 9:59:20 PM

Quote:
Reversing fan only works well with non-top designed HSF in general.

You mean changing the direction of the fan on the HSF? :eek:  I was talking about switching directions of the intake/exhaust fans.

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March 5, 2005 12:49:51 AM

What is MBM5. ANd yes my cpu temps are really that cool, right now they're 31 degrees at Idle. I think cool & quiet is active, I'm pretty sure I got the motherboard after the The bios update came out for my gigabyte GA-k8NS socket 754 board. My temps at fool load, after running 3d mark 1,3, or 5 and N-bench_V3 are usually about 42 to 45 degrees after a full 4 hour cycle. I'm going to put a top blow whole with a case fan sucking air out. I'm going to switch the fan around that blowing on the cpu around and the rear fan and see how much different the temps are.
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March 5, 2005 1:43:44 AM

<A HREF="http://www.majorgeeks.com/download.php?det=311" target="_new">MBM5</A>
<A HREF="http://www.google.com" target="_new">Google is your friend</A>
42-45C are good load temps. I don't think you have any temp issues. =/ long thread to figure that one out. Hey -at least you learned something!

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March 5, 2005 2:07:02 AM

well I was never really concerned about my temps, just wanted to see how cool i could get it for overclocking in the future without using water cooling. I like to find the easyest way to get stuff done without spending alot of money.
March 5, 2005 2:26:16 AM

It wont show the tmps. My motherboard is not supported. I have the gigabyte ga-k8ns socket 754. How do i get it supported??
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March 5, 2005 11:09:52 AM

What I had to do is just fool around with the setting untils I found sensors whose temps made sense.

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March 5, 2005 9:44:02 PM

I selected my board as being a GA-K8ns pro version. It's showing my case temps as being 25 degrees, funny thing is it never changes. But Im pretty sure the cpu temp thing isn't working right because it's registering the temps of my cpu as -2 degrees. my easytunes 4 shows my cpu temps as 30 degrees which is nice. it is also showing the speed of my fan 1, which I'm guessing is my cpu fan and fan 2 which is my case fan blowing on my cpu. what is core?? Is that the volts on my cpu. But what is core 1, +3.3, +5.00 and +12.00 mean?? It'a registering something but what that is i'm not sure. Hey quick question, I have the case fan as a thermal take smart fan 2. Now i have that fan hooked up to the 3 pin slot on my motherboard, is the 25 degrees that shows up on the case temperture what the thermal sensor that comes with the fan detecting. these smart fans have the thermal sensor to control the speed of the fan i just didn't know if it also shows those temps when hooked up to the 3 pin slot. What are some ways i can get the cpu temps read right?? dude for some reason my easytunes says my cpu fan is only running at 1834 rpms but the mbm 5 says it's at 3668 rpmsi hope i didn't do something to it. why are they reading two different rpms. I'm pretty sure the mbm5 is right because my cpu temps are fine .

<P ID="edit"><FONT SIZE=-1><EM>Edited by newdude on 03/05/05 06:50 PM.</EM></FONT></P>
March 5, 2005 9:59:40 PM

it was having some kind of comflict with the easytunes4.
March 6, 2005 2:20:14 AM

Listen, I found a marked improvement in CPU cooling when I did this -

1) one case fan blowing on CPU
2) two case fans drawing air into case.

This pressurized the case slightly so that there is more air molecules to absorb heat and also forced more air out through the PSU.

Result - 5'C cooler CPU and a much cooler 400W PSU.

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March 6, 2005 4:30:53 AM

Quote:
Ummm... isn't that kinda obvious how the case fans should be arranged?

Yes, intake one end and exhaust the other. If someone has some heating issues, then they can try switching intake/exhaust.
Quote:
Reversing fan only works well with non-top designed HSF in general.

I haven't dealt with a lot of side mount fans for HSF, so i didn't think about changing directions for those...

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