Thermal sensors of Phenom II

[dexman]

hi,

i have a Phenom II X3 710, enabling acc will unlock the fourth core. it's stable even when OC'ed. the thing is core temperatures will go crazy after acc is enabled.

i hear that Phenom II don't have thermal sensor for each core but use some formula instead to come up with core temperatures. could someone elaborate on that? also AMD Overdrive shows TMPIN 1,2 and 3 temperatures but i have no idea what these stand for. is there a way to find out the core temperatures with acc enabled? my board is Gigabyte GA-MA790XT-UD4P.

thanks for the heads up

[beta]

TMPIN1,2,3 are the mobo sensors, you can check the hardware monitor in the bios to find out which one is for the cpu.

[dexman]

but where would be the cpu sensor located? is it safe to say that cores temperatures are pretty much same as cpu temperature?

[beta]

core temp is usually greater.

to find out the offset of the onboard sensor, do a test run in prime with 3 cores, then while it's still running check the difference of the two temps.

[dexman]

sounds like a good idea. thanks beta

EDIT: i just tried it. surprisingly cpu temp was bigger than cores temp. from idle to prime95 burn, cpu temp 30°C->45°C, while cores temp 21°C->34°C. i checked with both AMD Overdrive and CPUID Hardware Monitor. i guess cpu sensor is located at the socket and heat builds up more there than at the chip.

[DedEmbryonicCe1]

Yes it's in the socket.

[beta]

I think your mobo sensor is not too well calibrated, but you can use the offset to calculate the core temp anyway.

[robbicfc]

I use Core Temp and generally find it excellent. One thing I have noticed is that when I unlock my Phenom II 550 to 4 cores, temps are no longer returned. Set it back to original and normal service is resumed.

[largon]

Yes it's in the socket.

Is not.
Definitely not in the socket.

i guess cpu sensor is located at the socket and heat builds up more there than at the chip.

That would be physically impossible.
What you're looking at is most likely the CPU VRM temp.

[ReKcOlNu]

Definitely not in the socket.

Right, years ago (4-6 years?) there was a sensor in the CPU socket, but since then all CPUs have had built-in thermistors to monitor and report the CPU temp so it's doubtful any board makers would still be using a sensor in the CPU socket.

AMD and Intel rate all their current CPUs max temp by Tcase, not core temp! You can not use core temp values and compare them to AMD's or Intel's max CPU temp ratings!

Tcase is the temp taken at the center of the metal lid on the CPU. A built-in Thermistor sensor in the CPU monitors the CPU temp which is also used to trigger a thermtrip event should its value be higher then the max temp rating of the CPU which the BIOS would then either throttle the CPU, shutdown the CPU or board. This same sensor is usually the single CPU temp reading you see in the BIOS and which many programs use after using a mathematical formula since the sensor is not actually in the center of the CPU metal lid.

The one big problem with reading CPU temps is AMD/Intel make many different CPUs which can all run on the same motherboard but not all chips may use the exact same formula to figure a CPU temp, so if the BIOS or program isn't updated to detect a CPU then most likely the reported temp is going to be incorrect.

There is more to a CPU then just the cores, on-die memory controller, L3 cache, etc, etc, all need to operate within a certain temp or they will error/fail, so to those who are reading core temps just remember you are not getting the whole picture nor can you compare those values to anything, for all you know a core temp may have a max temp rating of 125C but the whole CPU may need to be below say 70C.

[dexman]

thanks for the clarifications guys. both my bios and reading programs are updated. does it make any sense to you that reported cpu temp is bigger than cores temp?

i'm asking because i want to compare two coolers and therefore one additional core is better for testing + acc allows the better oc. is it ok to compare them based on cpu temp?

[ReKcOlNu]

Sure, you could use the core temps to compare different coolers on the same CPU and motherboard.

I'd also use the CPU temp reading in the BIOS and take a reading after about 10 minutes, the BIOS doesn't use/send any power saving features to the CPU and it puts a load on the CPU as well, when in the bios your CPU is using more power then it is in the OS at idle so your CPU temp in the BIOS should be higher then when idling in the OS. Even with all CPU power saving features disabled the CPU will still run cooler in the OS since the OS sends the CPU commands like HLT (halt) so the CPU uses less power when its not doing anything. For example I did a test using a Kill-A Watt meter on my x2-550BE system (unlocked to a X4 @ 206x17 - 3.5GHz) , when in the BIOS the pc eats 151W, in windows with Cool N Quite enabled it only uses 84W and 103W with Cool n Quite disabled. If I enable the "C1E" option in the BIOS the power usage drops another 5-6 watts in windows @ idle but had no effect on power usage when in the BIOS.

[dexman]

Sure, you could use the core temps to compare different coolers on the same CPU and motherboard.

my cores temp are not working when acc is enabled though. i can only use cpu temp to compare the coolers. even with three cores active and functioning cores temp, the cpu temp is much bigger than core temps.

[ReKcOlNu]

On my AM3 (MSI 770-C45 with a X2-550BE) the core temps are always 8C lower then the single cpu temp reading, and I know the core temps are BS because they are actually lower or about the same temp as the temp of the air going in my PC case! My s939 (Asus/4200+ X2) system core temps are about 5C lower at idle but closer to the CPU temp reading when under heavy loads. I just ignore core temps, AMD/Intel don't use "core temp" to rate the max temps of their chips so to me programs like "CoreTemp" are totally useless, you might as well weight the tires on your car to see if they have enough air in them.

[dexman]

my core temps are same as ambient air, it didn't make sense to me either unless Phenom stands for 'Phenomal in bending physics laws' i guess i'm going to use the cpu temp, thanks for the feedback

[deimos3428]

Just wanted to say thanks to ReKcOlNu for his advice in this thread. You wouldn't believe how hard it is to get the simple question of "which temperature sensor should I monitor when overclocking?" answered, and a lot of otherwise useful overclocking tools have it wrong in one way or another.

For example, if I give OCCT a "Max CPU Temp" of 62 (for my 955), it quacks out when any of the core temps (Core #x) reach that value, not the case temp (TMPIN0). This tends to happen much sooner than it should, but is easily fixed by telling OCCT that Core 1 is TMPIN0 and disabling the rest in the options.

To the original poster: I used to have a 710 as well. The core temps are ridiculously low for that proc and not to be believed at all. Yeah, they disappear when ACC is enabled -- but good riddance!