Newbie question about pwm control

TheApprentice · 11th Sep 2006, 07:46 AM

Hi guys
As you can tell from the name I am new here and am in need of some guidance.
I am not a stranger to bios settings but I am always willing to admit that I need help when I am stuck. I am currently trying to set up the pwm control on my Foxconn(!) mobo, and I don't quite understand a couple of the settings.

I got a Foxconn 945g7ma mobo (Intel 945 chipset-64 bit compliant), Pentium 4 630 3GHz Hyperthread cpu (emt64) with 4-pin cooling fan (retail package) and 1GHz of ddr2 ram (amongst other thing which don't actually relate to my question here)

I would like to know if anybody has any guidelines about setting two of the pwm values in the bios.
1. pwm start value (0~127)
2. pwm slope value (currently set to 2 pwm/c)

There are two other settings which relate to the pwm start temperature value and the full-on temperature value, quite straight forward.

What I cannot seem to achieve is a gradual fan-slope between the two temperatures, the fan is either idling at around 1300 rpm or full-on at around 4560rpm (or constantly start-stopping if the temp. is on the threshold of the full-on temperature). I was wondering if the two settings I mentioned above would allow for a gradual slope (if it is at all possible on this mobo), or whether I am stuck with simple "slow" and "full" control?

As mentioned, I have a 4-pin fan so I assume that I can have some kind of gradual speed control over the fan.

Any help would be most gratefully and humbly received at this point.

tia
TheApprentice

TheApprentice · 12th Sep 2006, 07:27 PM

Just an update here, I have set my pwm start value to 63, which according to MY theroy should start the fan at around half of it's rated speed (around 2300 rpm). BUT when I re-boot it goes right back down to around 1400(?)
It does kick to full power when it reached the specified "full-on" temp no problems.
I wonder if I have actually got this linear control capability on this board or whether it is a straight slow/fast switching thing?

Adrian Wong · 13th Sep 2006, 11:02 AM

Hmm.. Unfortunately, nope.

I'll need to do some research on this.

TheApprentice · 13th Sep 2006, 05:31 PM

Thank you, I appreciate the input. A real puzzler this one...

TheApprentice · 16th Sep 2006, 07:12 PM

Okay, another update on this one
From around 60% or the total rpm speed upwards, the pwm value will start the cpu fan speed at a value that is approximately the same percentage rate as x/127 (!)
However setting a value BELOW ~60% of the rpm speed will kick the fan controller down to minimum (~1500 in my case) regardless of the value entered. It seems there is a limitation in the fan controller, it can't control speeds below ~60% of maximum.

Let me make that a lot clearer - my pwm start value can be set to anything between 0~127. If I set it to 77 then this value represents (77/127)*maxrpmrate. In my case the maxrpmrate is ~4500rpm.

Using this calculation we get (77/127)*4500. Well 77/127=0.60, multiply this by 100 and we get a percentage of ~60%. If we calculate what 60% of the max 4500rpm would be then we get 2700rpm.

This is approximately what is happening, providing I set the pwm slope value to 2*pwm value/deg. C (default for my bios). I haven't yet played with this setting but I am assuming it affects the ramp rpm value from pwm start to maximum according to cpu temp. This would allow the rpm to increase in a non-linear ramp for smaller increases in cpu temp.

If anybody can clarify this then please do, I don't have a degree in maths so I am not very good at explaining this kind of thing.

Edit:
This works GREAT. I have found the optimum temp settings for my cpu just by listening to the fan rpm. Linear ramping works a treat!

11th Sep 2006, 07:46 AM	#1 (permalink)
TheApprentice Newbie Join Date: 11 Sep 2006 Location: UK Posts: 16 Reputation: 3 Rep Power: 0	Newbie question about pwm control Hi guys As you can tell from the name I am new here and am in need of some guidance. I am not a stranger to bios settings but I am always willing to admit that I need help when I am stuck. I am currently trying to set up the pwm control on my Foxconn(!) mobo, and I don't quite understand a couple of the settings. I got a Foxconn 945g7ma mobo (Intel 945 chipset-64 bit compliant), Pentium 4 630 3GHz Hyperthread cpu (emt64) with 4-pin cooling fan (retail package) and 1GHz of ddr2 ram (amongst other thing which don't actually relate to my question here) I would like to know if anybody has any guidelines about setting two of the pwm values in the bios. 1. pwm start value (0~127) 2. pwm slope value (currently set to 2 pwm/c) There are two other settings which relate to the pwm start temperature value and the full-on temperature value, quite straight forward. What I cannot seem to achieve is a gradual fan-slope between the two temperatures, the fan is either idling at around 1300 rpm or full-on at around 4560rpm (or constantly start-stopping if the temp. is on the threshold of the full-on temperature). I was wondering if the two settings I mentioned above would allow for a gradual slope (if it is at all possible on this mobo), or whether I am stuck with simple "slow" and "full" control? As mentioned, I have a 4-pin fan so I assume that I can have some kind of gradual speed control over the fan. Any help would be most gratefully and humbly received at this point. tia TheApprentice

13th Sep 2006, 11:02 AM	#3 (permalink)
Adrian Wong Da Boss Join Date: 10 Oct 2002 Location: In front of my BenQ Joybook 7000 notebook! Posts: 29,655 Reputation: 2846 Rep Power: 63	Hmm.. Unfortunately, nope. I'll need to do some research on this. __________________ Dr. Adrian Wong Tech ARP \| Blog @ Tech ARP \| The Free Trade Zone DYKT : The only offshore account I have is at the sand bank? Keep Tech ARP free! Visit our sponsors! We need PROGRAMMERS and TECHNICAL WRITERS! Contact us if you are a hot shot programmer or technical writer! My items for sale : 50x SD Card \| Memory Stick PRO \| Cyclone Energy Saver \| Seiko SS watch \| Tiger/Carlsberg beer jugs \| Travel Speakers \| Motorola V600 \| Nokia N90 SOLD! \| New Lowepro Mini Trekker AW Other items for sale @ the FTZ : Zalman CNPS9500 LED @ $20 \| Zalman CNPS7700 Cu @ $20 \| Zalman CNPS7000 Cu @ $20 \| Swarovski bracelet watches \| Dell 17" LCD \| Hi-Fi speakers \| English DIVX movies \| HP LaserJet toners! \| Office chairs

16th Sep 2006, 07:12 PM	#5 (permalink)
TheApprentice Newbie Join Date: 11 Sep 2006 Location: UK Posts: 16 Reputation: 3 Rep Power: 0	Okay, another update on this one From around 60% or the total rpm speed upwards, the pwm value will start the cpu fan speed at a value that is approximately the same percentage rate as x/127 (!) However setting a value BELOW ~60% of the rpm speed will kick the fan controller down to minimum (~1500 in my case) regardless of the value entered. It seems there is a limitation in the fan controller, it can't control speeds below ~60% of maximum. Let me make that a lot clearer - my pwm start value can be set to anything between 0~127. If I set it to 77 then this value represents (77/127)maxrpmrate. In my case the maxrpmrate is ~4500rpm. Using this calculation we get (77/127)4500. Well 77/127=0.60, multiply this by 100 and we get a percentage of ~60%. If we calculate what 60% of the max 4500rpm would be then we get 2700rpm. This is approximately what is happening, providing I set the pwm slope value to 2pwm value/deg. C (default for my bios). I haven't yet played with this setting but I am assuming it affects the ramp rpm value from pwm start to maximum according to cpu temp. This would allow the rpm to increase in a non-linear ramp for smaller increases in cpu temp. If anybody can clarify this then please do, I don't have a degree in maths so I am not very good at explaining this kind of thing. Edit: This works GREAT. I have found the optimum temp settings for my cpu just by listening to the fan rpm. Linear ramping works a treat! Last edited by TheApprentice : 17th Sep 2006 at 05:33 AM.*

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12th Sep 2006, 07:27 PM	#2 (permalink)
TheApprentice Newbie Join Date: 11 Sep 2006 Location: UK Posts: 16 Reputation: 3 Rep Power: 0	Just an update here, I have set my pwm start value to 63, which according to MY theroy should start the fan at around half of it's rated speed (around 2300 rpm). BUT when I re-boot it goes right back down to around 1400(?) It does kick to full power when it reached the specified "full-on" temp no problems. I wonder if I have actually got this linear control capability on this board or whether it is a straight slow/fast switching thing?

13th Sep 2006, 05:31 PM	#4 (permalink)
TheApprentice Newbie Join Date: 11 Sep 2006 Location: UK Posts: 16 Reputation: 3 Rep Power: 0	Thank you, I appreciate the input. A real puzzler this one...