Question AMD FX-8350 Throttling, High CPU Temperature but low Core Temperature?

Jun 8, 2021
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Hello!
I've got a problem with my rig throttling under heavy load despite individual core temps being below the threshold by a long shot.
Rig Specs
CPU: AMD FX-8350
MB: Asrock 970 Pro 3 R 2.0
RAM: DDR3 4GB Kingston HyperX 1026MHZ (X3) (12GB Total)
Graphics Card: Nvidia Titan X GTX
Cooler: Gamerstorm 120mm Watercooler
PSU: Corsair HX1200

I had a problem with the CPU getting so hot it cut out the PC, after a lot of troubleshooting attempts (reapplying thermal paste, changing fan headers for the pump, rad relocation etc.) I tracked the problem down to corrosion blocking up the fins inside the pump, after cleaning and reassembly the pump works perfectly and doesn't run at full speed continuously as it was. CPU Core temps now sit at 20C on idle and up to 55C on load.

I now have the weird problem of the CPU Sensor registering as 25C hotter than the Core temps. This then makes the CPU throttle under load even though all cores are well under the limit!

I've tried turning off the throttle in the Bios but the CPU still does it when it hits 70C despite the setting being off...

I'm at a loss as to what this could be any help would be much appreciated!
 
Jun 8, 2021
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The only way to get an accurate temperature measurement for FX is to use AMD overdrive and get a thermal margin reading. What does that say?
OverDrive is giving 50C margins on idle. When I run the stability test the margin never goes below 20C but its still throttling by dropping the multiplier down from 20X to 7X.
Its running at 4400MHZ at 1.365V
North Bridge at 2200MHZ at 1.2V
Hyper Transport at 2640MHZ

Any Ideas?
 

Phaaze88

Titan
Ambassador
Motherboard VRMs throttling the cpu via either power throttling, thermal throttling, or both.
1)A 4+1 phase - kinda weak to be using with a FX-8350.
2)No VRM heatsink.
3)A hybrid cooler in use instead of an air cooler; the former does not provide as much direct airflow over the VRMs compared to the latter.
 
Reactions: Rogue Leader
Jun 8, 2021
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Motherboard VRMs throttling the cpu via either power throttling, thermal throttling, or both.
1)A 4+1 phase - kinda weak to be using with a FX-8350.
2)No VRM heatsink.
3)A hybrid cooler in use instead of an air cooler; the former does not provide as much direct airflow over the VRMs compared to the latter.
ahh so the CPU Sensor is picking up the VRM that makes sense. What`s the best way to stop it cooking short term? Drop the HT speed? CPU voltage/Multiplier?
and is it worth getting a separate cooler for the VRM?

Also why do you say 4+1 Phase is bad for the FX-8350?
Thanks for helping!
 
Jun 8, 2021
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Drop the max turbo frequency. It's normally 4.2ghz

I'm not sure it's worth spending much money on the old AM3+ platform.
Have done and is now keeping inline with the CPU core Temp Excellent!!
I'm trying to stretch my rig out till I can afford the cost of a completely new system, not looking to part with the better part of a Grand atm!
its just the CPU which is only just bottlenecking on the Newest games running at top settings, If I can get a Reasonable VRM cooler can I clock it back up to 4.4GHZ? The Tech may be getting on but she still games with the best!
Your Help is most appreciated!
 

NightHawkRMX

Polypheme
Ambassador
Another solution is to take a fan and put it over the vrm. This will provide airflow and reduce temps for much less money than the cost of a new board.

4+1 phase is what I would expect on a low end board, not a mid range 970 chooser. Not very good, especially not for a 125w part.
 
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What`s the best way to stop it cooking short term?
.....
In addition to locating a fan to blow air across them you can glue heatsinks on the FET's. The FET's are are the square, black, fairly flat devices (10 of them on your board) nestled close to the 5 cube shaped inductors. This isn't as good as a proper heatsink but anything that increases surface area helps dissipate heat to the air stream, delaying thermal throttling.

But another thing that might be throttling your CPU is APM. If enabled, APM will try to keep the CPU within it's TDP rating even if it's overclocked. That might be a good thing in your case since if a 125W rated CPU is rough on it removing that cap will just stress the VRM even harder. Some motherboards have a BIOS setting to disable it although it might have a strange name: on my son's Gigabyte it was labeled "high performance mode".

Honestly though, if your motherboard doesn't report temperature of the VRM FET's then you should get yourself a decent IR temperature probe. You need to know what the FET's are doing temp-wise or you can toast the underlying PWB material before you're ready to upgrade.
 

mamasan2000

Distinguished
I used to have a FX-8350. I did not trust any temp under 40 C. Just how AMD set it up and calculated it. Because it is calculated under 40 C. It is wildly innacurate under 40 C.
I didn't try AMD Overdrive, I don't think. Max temp is 61 C for the CPU IIRC. TjMax.

The FX-8350 is a 4 Ghz CPU all-core, by default. It might boost to 4.2 but never 4.4. So your multiplier must be 22. I overclocked it so I turned off turbo boost, core boost stuff, the stuff resposible for 4.2 Ghz boosting. I never even tried it.

For me, 4.5 - 4.6 Ghz was running for a couple years, then degraded. Dropped that down to 4.4 Ghz. Brother still uses that PC.
 

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