FX 8350 - Inaccurate Core Temperature

Hey kids,

I have an AMD FX 8350 and I love it, but I can't seem to get an accurate core temp out of it. AMD says that it uses a different algorithm to calculate the core temp, and that it's only accurate under load.

I can accept that, but under load (Prime95 for an hour), my core temp is 20 degrees lower than the socket temp, and it's consistent (Socket: 49C Core: 29C @ 4.2 GHz). All core temps seem to be 20C lower than the socket temp under any load. Has anyone else with an 8350 noticed this? Would this 20 degrees be a reasonable fudge factor when overclocking?

I haven't really OC'd this rig too much because of the core temp thing but I'd like to push it a little. I'm running on air cooling so an extreme OC is out of the question but right now temps are about 50C for socket temp and core should be a little higher after running on full load for a while. I just can't get my head around this 20 degree difference.

Any 8350 owners have a similar experience?

i ususally never let core go above 65C in prime. i could also never get a core temp either with all the programs ive tried. the ONLY program i could use to get a temp was AI suit

I go by what Core Temp (the program) tells me. Mine on a water cooler is as low as 17C idel and running prime 95 is about 44C. If you wait a day or 2 I can tell you what it is on air. My FX8320 is 42C on prime 95 clocked at 3.7 Ghz by the Sabertooth motherboard. The cooler is a Coolermaster Hyper 212 with Push Pull fans.

Mellon Head said:

Hey kids,

I have an AMD FX 8350 and I love it, but I can't seem to get an accurate core temp out of it. AMD says that it uses a different algorithm to calculate the core temp, and that it's only accurate under load.

I can accept that, but under load (Prime95 for an hour), my core temp is 20 degrees lower than the socket temp, and it's consistent (Socket: 49C Core: 29C @ 4.2 GHz). All core temps seem to be 20C lower than the socket temp under any load. Has anyone else with an 8350 noticed this? Would this 20 degrees be a reasonable fudge factor when overclocking?

I haven't really OC'd this rig too much because of the core temp thing but I'd like to push it a little. I'm running on air cooling so an extreme OC is out of the question but right now temps are about 50C for socket temp and core should be a little higher after running on full load for a while. I just can't get my head around this 20 degree difference.

Any 8350 owners have a similar experience?

"Starting with the Phenoms, AMD's digital sensor no longer reports an absolute temperature value anymore, but a reading with a certain offset, which is unknown. It is estimated that this offset is between 10 - 20c."
ALCPU Forums ? View topic - Core Temp - FAQ
If you assume the worst-case scenario 20°c offset, your core could very well be running at 49°c under load, the same as the socket. If I were in your shoes, I'd assume that's the case.

I made a ballpark estimate of offset by letting my rig idle and do nothing for half an hour. I added 9°c to my idle temp to make it a 2 or 3 degrees Celsius warmer than the ambient room temp. So when the room is 25°c and I'm running at 100% for at least a half hour, CoreTemp reads 46°c. In summer, room temp gets up to 35°, so my CPU reads anywhere from 55°-57° at 100% load.

Don't use Core temp with an offset for AMD cpu's as your load temps will be way off the true value. Use either HWinfo64, MWmonitor or Aida64 and they will all show 2 values, 1 for the socket and 1 for the core temp. The socket temp is what you should look to if you want an idea of idle temp's and the core temp for load temp's. The reason for this is as stated before AMD use some odd way of measuring the cpu temp and it's not accurate below 40-45c AMD Temp Information and Guide

What is "Core Temp" ?

"Core Temp" is what AMD refers to as "TCTL" and is a non-physical temperature on an arbitrary scale measured in degrees. It does not represent an actual physical temperature like die or case temperature.

What is "CPU Temp" ?

"CPU Temp" is read by a sensor in the socket of the motherboard.
It is a physical temperature and therefore will be effected by ambient temps inside the case.

Why should I use "Core Temp" and when?

AMD designed this equation to accurately read peak (45C+) and load temps. It has an equational offset to determine said temps which equalizes at 45C. Since it's designed for peak temps and is a non-physical temperature it cannot read idle temps or account for ambient temps correctly.

So what is "CPU Temp" good for then?

At peak temps this value is typically 7-10C higher (depending on motherboard) than the actual temp due to it being a physical sensor. At idle it's a little more accurate, but still not dead on, and besides idle temps do not matter near as much as load temps do.

In my screenshot of HWinfo64 you can see 2 temps which have been re labled to show

OvenMaster said:

"Starting with the Phenoms, AMD's digital sensor no longer reports an absolute temperature value anymore, but a reading with a certain offset, which is unknown. It is estimated that this offset is between 10 - 20c."
ALCPU Forums ? View topic - Core Temp - FAQ
If you assume the worst-case scenario 20°c offset, your core could very well be running at 49°c under load, the same as the socket. If I were in your shoes, I'd assume that's the case.

Yeah, it seems to me that after about an hour, the socket and core temp should be roughly equal. The core temp a little higher actually. That seems to be about 20 degrees.

madcratebuilder said:

[BINGO!

I've had three different FX cpu's in the past year that have been used with just about all the different monitoring software. Idle core temps always read low until you get above 40C+/-.

The consistent monitors are HWinfo64, MWmonitor, Aida64 and Open HWM. HWinfo has a forum and the developer is very active in it. Aida64 is more than just a monitor and it's about $30 for the registered version, worth it IMHO. Aisa64 also supports LCDstats, Goverlay and Aquacomputer hardware, as does OpenHW on a limited basis.

I'll try HWinfo64, I was using CPUID's HWMonitor.

I know that the cores will read low until they get above 40 - 45 degrees, but even above that, mine don't read right. I find that really weird, but maybe it's my temp software. Black edition chips are meant for overclocking, they should have a reliable core temp measurement. Are you listening AMD?!?!

This is the result of using HWinfo64 and prime for one hour:



Something isn't right here. Maybe my CPU just doesn't read correctly. It's above 45 degrees, but it doesn't read the way that AMD says it should. My core temp should be reading at least 50 by now...

Mellon Head said:

This is the result of using HWinfo64 and prime for one hour:



Something isn't right here. Maybe my CPU just doesn't read correctly. It's above 45 degrees, but it doesn't read the way that AMD says it should. My core temp should be reading at least 50 by now...

Those are very strange readings.

Post those at the HWInfo64 forum. Martin should be able to shed some light on this. I suspect it's a funky motherboard sensor(s).

ETA: Read some threads about inaccurate temp reading and a few had devolved after a BIOS change. Maybe try a different BIOS version for the mobo and see if it changes. You can always go back to the version you have now. Some had more accurate reading after a new or different BIOS.

You guys should give OCCT Home a try,

I've seen OCCT and plan on some testing with it if I ever get this new box finished. I really like the charts generated.

I'm using a Aquacomputer AQ6 for monitoring the loop, fan and water pump control. The AQ software is limited on what monitoring software it can interact with. Limited to Adid64 or OpenHW for now, AQ may port for HWInfo64 soon.