PWM High on IP35-E

[sjordan]

Originally posted by: SerpentRoyal
It appears that cold air was not getting to the PWM heat sink (base of HS is hot). At 53C PWM, my heat sink is barely warm to the touch (about as warm as the base of the BT).

A quad can draw a lot of current from the output devices. If your case does not provide adequate air flow to the PWM HEAT SINK, then the output devices will run HOT. It's very important to control PWM, NB, and SB temperatures when you overclock a quad.

Don't take this as rude, take it as someone who doesn't understand.

How is pointing the spot cool directly over the PWM heaksink not adequate air flow, and how is this any different then putting a 40mm fan to the PWM heat sink? Yes I know it will provide a little more air flow, but the spot cool is doing the same thing. Could it be that I have a setting fudged somewhere?

 

[SerpentRoyal]

That's an 80mm fan. I'm not sure if you could position this fan 1/2" above the PWM heat sink to cool it. The effectiveness of a fan decreases sharply with distance. You can significantly improve cooling by strapping a 40mm fan directly to the PWM heat sink.

I don't think the setting is fudged. Case temp and CPU temp look okay. The base of the PWM heat sink is much hotter than the base of the BT heat sink. This tells me that the heat remains trapped on the heat sink because you don't have sufficient air flow over the cooling fins to cool the output devices.

Note that the $90 Gigabyte board uses NO heat sink for the PWM. These output devices can safely run up to about 100C, but you want to keep them under 70C for best stability at high CPU core speed.

Also note the large jump in idle vs load PWM temps...55C to 100C is a huge jump. The heat sink can only draw heat away from the output devices (gets very warm). Cold air must flow across the fins to cool the heat sink. Without air circulation, you will see a LARGE build-up in temperature at the heat sink.

 

[sjordan]

Well I have another case I am going to try out when I get a chance and see if the results are the same. I also have a fan laying around that should be perfect for the PWM.

 

[SerpentRoyal]

Test the MB outside the case with a small fan strapped to the top of the PWM heat sink (blow down into the MB).

My Antec SLK3000B has room just above the 4/8 pin plug for a high speed 80mm or 92mm fan. Aim this fan toward the base of the PWM heat sink. You should be able to position the fan within 1.5" of the the PWM heat sink.

 

[sjordan]

Ok, I got the board outside of the case and ran the machine...this was a huge Pain in the butt, but I did it

Anyway I put a fan directly on the PWM and did notice a small change, however it still climbed up to 100C...this time around it just took longer....about 8 minutes into Prime95 opposed to 5.

 

[SerpentRoyal]

Not sure what to tell you. If cold air doesn't lower the PWM temp, then I have no cheap solution. There is obviously good contact at PWM heat sink. For whatever reason, you cannot effectively remove heat from the heat sink with cold air blowing over the fins. Only rational explanation...the rig resides in a vacuum.

 

[sjordan]

Could a faulty power supply cause the PWM to raise to high?

 

[ArchAngel777]

Originally posted by: sjordan
Could a faulty power supply cause the PWM to raise to high?

Nope...

 

[sjordan]

Ok for the heck of it, I changed out the powersupply. Now, this may catch some of you by surprise but this change now has my PWM peak at only 85C. Both of the power supplies are Antec True Power 430watt. I may end up tossing both of them and look for a good 500Watt.

 

[ArchAngel777]

I do have one more suggestion for you... It is your last and only hope... Remove the Heatsink and clean up the bottom of it, apply a thin layer of AS5 to it and remount.

Ok, if we go back to heat transfer, we know a few things.

If the PWM is 100c, then if the heatsink is properly attached, it should be within 5c of that temperature... If you can put your finger on the heatsink for more than a second, you either do not have good contact with the PWM/MOFSETs region, OR they really are not running as hot as they are reporting.

If it does burn your fingers, then the heat transfer is doing as it should, but you are unable to dissipate that heat... Now, I am the type of person that typically is not going to spend more than the motherboard costs to cool it. So, if you bought this board for $71, I wouldn't put anywhere near that ammount into it to cool it, but that is just me... Other people spend probably 500-600 on new heatsinks for SB/NB/PWM/RAM/CPU/GPU + Water cooling setup... That isn't for me, not unless I had money to spare. Anyway, not to get on a tangent. But if you asbolutely want to lower PWM temperatures, you will probably need to look into a larger heatsink for that area and then active cooling for it.

 

[ArchAngel777]

Originally posted by: sjordan
Ok for the heck of it, I changed out the powersupply. Now, this may catch some of you by surprise but this change now has my PWM peak at only 85C. Both of the power supplies are Antec True Power 430watt. I may end up tossing both of them and look for a good 500Watt.

I am extremely suprised... Almost to the point where I don't believe it... But, whatever works, works.

Just a fair warning though... I have a high quality Antec TPQ 850 WATT 88%+ Efficiency and still run a fair bit warm in the PWM region... So, I wouldn't expect much more than what you have already seen...

 

[SerpentRoyal]

Originally posted by: ArchAngel777
I do have one more suggestion for you... It is your last and only hope... Remove the Heatsink and clean up the bottom of it, apply a thin layer of AS5 to it and remount.

Ok, if we go back to heat transfer, we know a few things.

If the PWM is 100c, then if the heatsink is properly attached, it should be within 5c of that temperature... If you can put your finger on the heatsink for more than a second, you either do not have good contact with the PWM/MOFSETs region, OR they really are not running as hot as they are reporting.

If it does burn your fingers, then the heat transfer is doing as it should, but you are unable to dissipate that heat... Now, I am the type of person that typically is not going to spend more than the motherboard costs to cool it. So, if you bought this board for $71, I wouldn't put anywhere near that ammount into it to cool it, but that is just me... Other people spend probably 500-600 on new heatsinks for SB/NB/PWM/RAM/CPU/GPU + Water cooling setup... That isn't for me, not unless I had money to spare. Anyway, not to get on a tangent. But if you asbolutely want to lower PWM temperatures, you will probably need to look into a larger heatsink for that area and then active cooling for it.

He said the base of the PWM HS is making good contact with the output devices. Also, the bottom of the PWM HS is hot when priming. Translation...there is adequate heat transfer to the HS. Cooling efficiency also increase as the delta T between air and HS goes up.

The PSU will only respond to the command of the CPU. If you suspect a defective PSU, then grab an Antec Earthwatts 500 from the local Staples.

A lot of stuffs in this thread make zero sense. How can a high speed 80mm positioned right on top of the PWM HS yield zero improvement when the ambient temp is approximately 25C?

Another user with GO Q6600 and IP35-E @ 3.8GHz. 62C PWM under Orthos/Prime.

http://forums.anandtech.com/me...d=2063989&STARTPAGE=56

 

[hokiealumnus]

For the record, AS5, when at high temperature (100c would qualify!) can become conductive. Conductive material + PWM chips = BAD. That's why I got Ceramique...though it is on the sticky side for my tastes, but it does the job.

 

[NoelS]

Folks,

If sjordans PWM runs at 72C with the HS off and a fan pointed at it, wouldn't he be better off running without the heat sink? What would be the problem with doing that?

Noel

 

[SerpentRoyal]

That's 72C idle, not load.

 

[ArchAngel777]

Originally posted by: SerpentRoyal
That's 72C idle, not load.

Lol! The thing would melt at load...

 

[SerpentRoyal]

Plenty of boards without MOSFET cooler...the cheap Gigabyte and the EVGA 650i, for example, don't have a PWM heat sink.