Sub ambient air cooling (?)

[Magicpandajuice]

I have an old MSI p55-a33 motherboard with a AMD a4-3300 APU thst I’ve recently been messing around with, its on an open air bench with a somewhat decent offbrand Chinese CPU cooler, I set the fan speed to 100 percent to do a stress test and I realized my idle temps are anywhere from 9-15 c, while my house sits around 20 c, is it just possible that the motherboard is reading the wrong temperatures or is it possible that it’s actually running below ambient on just regular air cooling?

[rockybulwinkle]

That sounds like some error in the measurement to me. It shouldn't be possible to get subambient with just air.

[Kilrah]

Motherboard is reading wrong. Unless you have water spilled on your cooler, but that wouldn't be good  

[Applefreak]

Yeah you are getting the wrong sensor data here. Unless it is a peltier-hybrid-cooler, you can't achieve sub ambient temperature.

[aisle9]

An air cooler relies upon pushing air through a fin stack. The purpose of doing so is to reduce the temperature of the fin stack, which pulls heat away from the CPU. Because the cooler relies on drawing air at ambient temperature through metal at temperatures above ambient, there's no way within the laws of physics to get sub-ambient temperatures from an air cooler in normal operation. You could do it by directing an air conditioner's flow straight through the fin stack, but not only is that impractical, it's a terrible idea as condensation will form and kill your board when it starts dripping on VRMs.

 

In short, your board's sensor is messed up. Not an uncommon thing to go out of whack on older boards. I ran a Q6600 on an old LGA 775 board that constantly wanted to tell me the CPU was running at 10C in a room with an ambient temp closer to 24C, and didn't have any other issues from the day I bought it through the day I sold the system.

[Magicpandajuice]

2 hours ago, aisle9 said:

An air cooler relies upon pushing air through a fin stack. The purpose of doing so is to reduce the temperature of the fin stack, which pulls heat away from the CPU. Because the cooler relies on drawing air at ambient temperature through metal at temperatures above ambient, there's no way within the laws of physics to get sub-ambient temperatures from an air cooler in normal operation. You could do it by directing an air conditioner's flow straight through the fin stack, but not only is that impractical, it's a terrible idea as condensation will form and kill your board when it starts dripping on VRMs.

 

In short, your board's sensor is messed up. Not an uncommon thing to go out of whack on older boards. I ran a Q6600 on an old LGA 775 board that constantly wanted to tell me the CPU was running at 10C in a room with an ambient temp closer to 24C, and didn't have any other issues from the day I bought it through the day I sold the system.

See, what’s really confusing me is that when I put it under load (not hard, opening chrome uses 80 percent of the old duel core cpu), it jumps to around 30 or so or even higher under sustained load

[aisle9]

8 minutes ago, Magicpandajuice said:

See, what’s really confusing me is that when I put it under load (not hard, opening chrome uses 80 percent of the old duel core cpu), it jumps to around 30 or so or even higher under sustained load

Some of those older AMD chips had serious issues with the temperature sensor, and would do silly things like report 50C when the CPU was actually closer to 70C. I don't know if the A4-3300 was part of that, but your description kind of sounds like it is.

[LogicalDrm]

17 hours ago, Magicpandajuice said:

See, what’s really confusing me is that when I put it under load (not hard, opening chrome uses 80 percent of the old duel core cpu), it jumps to around 30 or so or even higher under sustained load

The sensor is probably configured to use some set temp as baseline. Like 30C for example. So 7-15C low load would translate to 37-45C, which is about normal idle for any CPU under air cooling. That would bring 30C load temp to 60C actual load temp, again within reason.