The only temp tool you should ever use ever is CoreTemp. And we're talking about LOAD temps, your idle temps don't mean shit. Also even if you can only read 2 cores, its not like 1 core is going to be 40 while 1 is 80, that can't happen, they're all right next to each other. The most you'll get is a 5c difference which is nothing.
The temperature shown in the bios isn't exactly a load temp, but it isn't idle either. The CPU will heat up more when in the bios than when idle in Windows or just about any OS, because the bios doesn't run the code that actually makes the CPU be idle. If there was a CPU usage meter there, it would always show 100% because of that.
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The only temp tool you should ever use ever is CoreTemp
I donno, my processor isn't supported by CoreTemp, but other programs like RealTemp detect its temperature just fine
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