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OTES MOSFET Fans

H

Hardflip

n00b
Joined
Jul 24, 2005
Messages
15
I've noticed my OTES fans on my Abit Fatal1ty AN8-SLI seem to be a little too noisy. I can blow on them lightly to slow them down and see if it's there where the noise is coming from, and it is. The uGuru panel on my case reports 1 as 5900RPM or so and 2 as 5600RPM or so.

I'm just wondering if there's any way of quietening these things down. It also reports my CPU around 41c idle or so. But it reports room temperature as soon as I've booted at around 25-6c, which is about 5c off of what my thermometer is telling me here, so I'm guessing it's overmeasuring.

Having looked through BIOS I can see you can edit low and high temp boundaries in FanEQ as well as voltages. If I want to quieten these things down what would be an acceptable change and how do I do it? Surely the mosfets can't get that hot. Just note my motherboard is upside down (Lian Li V1000) and I'm using a stock HSF for the AMD X2 4400+ (got heatpipes so it's pretty good).

The air coming out of it is no where near as hot/warm as my PSU or outtake fan either, so I'm guessing it isn't doing that much. Any help is appreciated.
 
Hardflip said:
room temperature
Click to expand...


??? there is a sensor outside of your case???

its just a single spot on the mobo the temperature gradient and airflow pattern throught the rest of the mobo enclosure is unknown till you map it, that sensor could be low, high or accurate for its position, and you could have undetected hotspots elsewhere

to address the question, sure there are always alternatives, a little duct work and a swap out for a quiter fan could likely equal or better the current thermal solution

the thing about any single component be it a mobo, a PSU, graphics card or CPU heatsink is that its "solution" is limited to its form, whereas you can determine what its overall environment is like and secure it a cleaner and cooler air supply to work with
extending its "form" and solution with a deflector, a duct, or a fan at the right place ;)
(even sometimes by removing a fan in the wrong place)

heat transfer is all about differential temperatures, lower the air temperature its working with and it will move more heat for the given air volume (mass) and the static interface (size of the heat source \ total convection area)

are you sure its the mosfets or is it possibly cooling the VRMs?
(Voltage Regulation Moduals) which can get very very hot these days ;)
 
replace the fans, from what i hear the stock otes fans arnt so hot, i never had a otes fan, bought a sunon and 5v'd it
 
Ice - it's not a sensor I'm measuring the real room temp from, it's a traditional thermometer. Room temperature in the UK averages 21c and it's not that hot today. The 'room temperature' sensor in the PC however displays 25-6c even if I haven't used it in the last 12 hours.

You can see the OTES fans cooling the MOSFETs here for yourself - http://www.xbitlabs.com/articles/mainboards/display/abit-fatal1ty-an8_6.html and the BIOS FanEQ thing here - http://www.pcperspective.com/images/reviews/163/bios20.jpg

I really don't want to swap them. If they're not bringing out the that much hot air and the MOSFETs don't get hot, I might as well slow them down or turn them off. If you were to look in my PC you'd see the air flow is a little bit of circulation - http://www.lian-li.com/Product/Chassis/M_V_C_PC-V1000plus.htm

The back fan by the I/O faceplate takes in air, the HSF is right by it, so it uses that air, and then I'm guessing the hot air from that goes out the OTES fans, but it doesn't seem to be pulling any 'warm' air. The air removed is mildly above room temp.
 
air coming out of my otes fan is nearly hot, but under load my pwn temp gets as high as 50C, dont remember what it is normaly, only looked at it after doing a reverseing air flow experiment on rad, gonna revert it if temps arnt better by the time i get home, really gotta stop messing with multiple things at the same time, makes it hard to single out what made bad changes
 
Hardflip said:
Ice - it's not a sensor I'm measuring the real room temp from, it's a traditional thermometer. Room temperature in the UK averages 21c and it's not that hot today. The 'room temperature' sensor in the PC however displays 25-6c even if I haven't used it in the last 12 hours.

You can see the OTES fans cooling the MOSFETs here for yourself - http://www.xbitlabs.com/articles/mainboards/display/abit-fatal1ty-an8_6.html and the BIOS FanEQ thing here - http://www.pcperspective.com/images/reviews/163/bios20.jpg

I really don't want to swap them. If they're not bringing out the that much hot air and the MOSFETs don't get hot, I might as well slow them down or turn them off. If you were to look in my PC you'd see the air flow is a little bit of circulation - http://www.lian-li.com/Product/Chassis/M_V_C_PC-V1000plus.htm

The back fan by the I/O faceplate takes in air, the HSF is right by it, so it uses that air, and then I'm guessing the hot air from that goes out the OTES fans, but it doesn't seem to be pulling any 'warm' air. The air removed is mildly above room temp.
Click to expand...

Ice Czar was suggesting that your "room temp" sensor inside your PC case is not an accurate measurement of room temperature since it takes a reading from one isolated point on your motherboard. Unless you measure this after having the PC off for a while so that it has equilibrated with room temp, it is most likely not going to give an actual room temp measurement.

If you are saying that you're using the CPU temp sensor to measure room temp, then that's also not accurate- the chip begins heating up as soon as you turn it on.

As far as your MOSFETS go, it seems that all power regulation/switching devices get pretty hot these days. If you are at all concerned with maximizing your overclock, then you should have some kind of forced-convection cooling setup for them.
 
MOSFETs used for the processor voltage regulator
Click to expand...

in other words the mobo's VRM, so max the CPU and your looking at considerable heat
on my K8W the VRMs get hotter than my chipsets
( I actually have 3 chipsets :p )


its not a "room temperature" sensor on the mobo its an "in case ambient" sensor and a 5 degree difference isnt all that unusual, there is likely some miscalibration but then its measuring only a single spot, turn on the computer the CPU heatsink might be washing over it immediately and could easily account for a 5 degree difference even at idle and just showing the BIOS screen

as far as that case and the OTES suystem, that case has some rather specific airflow attributes, but Id guess your getting a fairly healthy amount of recirculation considering the proximity of the OTES exhaust to the CPU intake, note how the PSU exhaust is angled away from that area below it (to the side) and how the "case" exhaust is above it (since heat rises not much of an issue), but with the OTES system right next to the CPU air intake its likely to be redrawn back in, Id personally add either an intake duct to the outside of the CPU duct to isolate it more, or angle the OTES exhaust the same direction as the PSU is being angled with a duct, or more than likely both.

as far as disabling the fans, I wouldnt personally do that as I mentioned the VRMs can get pretty hot, andthe OTES system was designed to help cool them, Id guess they might be getting a bit "starved" by the current airflow pattern (hard to tell If they are thermally controlled fans, that might be why they are so loud)) and I would personally look at reversing them having them blow into the case and exhausted above by that case's blower and possibly use much slower fans.


I think a little experimentation is in order, ideally with a movable sensor like in the DigiDocs (which is what I use) CompuNurse's are cheaper though

IMO that mobo and case likely don't play very well together in a stock config
from what I can tell, just by looking at those links ;)

Good Luck
 
Just to clear some things up -

By 'traditional thermometer' I was referring to the wall thermometers you get with the red liquid that measures room temperature. I was comparing that to what the uGuru tells me. The uGuru will tell me the room temp even if the PC isn't on - so even after 12 hours of non use it's usually 25-6c or so. This is why I'm saying it might be inaccurate by about 5c or so, but it might be isolated to that censor.

As for the OTES fans - I don't believe I could get a duct for them, and even so, I doubt it'd change the noise level. After looking around it appears they run based on CPU temperatures. If I'm over 40c they kick in. All I was wondering was if I could slow them down via the BIOS by increasing the low/high temp controls.
 
Okay, time to experiment.

I just went into FanEQ and set it to 'enabled' for OTES 1 + 2. I then left it for a few minutes and noticed there was a 1-2c increase in system and power management temperatures. Looking at those temperatures now after using Windows for about 5 minutes with a few apps open, they seem to have stabilized to what they were before.

It appears without FanEQ the OTES fans seemed to go at full speed. I've read stories of people averaging 4000-5000 when under load. Mine nearly gets to 6000. I've also noticed that the majority of my fan sound was coming from these. I thought it was my HSF; but no, that's actually almost silent.

With the 35-45c temp settings in place I assume my system will shut down if it overheats, right? I just want to make sure I'm not frying my motherboard here. The HSF should be pushing air into the heatsink fan and around the CPU area, and that should be sufficient cooling - my heatsink is not too hot to touch. I'll report back after playing Half-Life 2.
 
Hardflip, have you read the manuals? cause I seem to remember it actually goes through uGuru & OTES in some decent detail.
 
With the manuals I've got they don't seem to tell me much about it, other than what they do in minimal detail and how to enable them.

Just played 10 minutes of HL2. The OTES fans kicked in to about 4200-4400rpm, used to be 5700-5900 (full speed), after my SYS temp reached about 38c (usually 34c). Seem much quieter, yet not bringing out what you'd consider 'warm air'. Do you think my current settings are safe for cooling the MOSFETs?
 
from what ive read here so far i'd say so...... i think you are good and have you gotten them quieter in the process?
 
Hardflip said:
With the manuals I've got they don't seem to tell me much about it, other than what they do in minimal detail and how to enable them.

Just played 10 minutes of HL2. The OTES fans kicked in to about 4200-4400rpm, used to be 5700-5900 (full speed), after my SYS temp reached about 38c (usually 34c). Seem much quieter, yet not bringing out what you'd consider 'warm air'. Do you think my current settings are safe for cooling the MOSFETs?
Click to expand...

The tweak you did should be safe. MOSFETs are very tolerant of heat. Also if you think about it Abit is one of the few mobo companies that has active cooling on the PWM. My OTES fans on my AN8 SLI Fatal1ty usually don't even spin up. Right now my PWM is at 39C. On DFI mobos I have seen the PWM temps get over 50C with no issues so I think you are more than safe. BTW my case temp is 28C and my cpu is 22C <---watercooled. Just for reference I am running bios 17.
 
Rolio - yes, at 4400rpm they are quiet, although my system is very quiet when they turn off all together. 5900rpm leaves a piercing sound that I could hear from downstairs with no ambient noise. Was annoying as hell.

AAC - My PWM is 37c right now. Thanks for the post.
 
Hardflip said:
I don't believe I could get a duct for them, .
Click to expand...

unbreakable.jpg


paper cardboard plastic metal it doesnt make much difference
sissors and tape + 5 minutes and youd have a test prototype
and if it is a thermally controlled fan like you say it will make a difference in the sound signature


based on my current understanding this is what is happening
current.jpg

the OTES in dark orange recirculating back into the intake


while Im propsing this as a solution
proposed.jpg

the green a small deflector

sorry about the sketch quality, the tablet isnt hooked up to this computer :p

adding say a three inch shield to the air intake would help too
 
i noticed that when i reversed my air flow, the otes exausts a lot of heat and didnt think that it would recirculate the otes fan
 
Id actually play around with three possible prototypes


propos4ed.jpg


intake shroud green
exhaust blower deflector blue
otes defector purple
 
Ice - cheers a bunch for the diagrams. I'll try finding a bit of perspex and cutting it to see if diverting the OTES exhaust does anything for my system. Been running my PC at least 10 hours since I changed my FanEQ and all is good. Temperatures a fine and noise is minimal (I don't even have to crank WinAmp up to hear it :D). I've also noticed the air coming out of the exhaust by the GPU and Sound card is colder than it was, probably due to the non-recycling of air whilst the OTES fans aren't on. Graphics card is also at 55c when it used to average 57c.
 
like any "built" system its all in the fine tuning,
OEMs model their offerings with CFD (Computatuional Fluid Dynamics) Software,
we get trial and error :p


sounds like you have a good start
Good Luck ;)

PS, Ive always found prototyping in a thick paper enough for testing
if the results warrant it, then I go to something more permenant and labor intensive ;)
 
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