Thanks for sharing your experience! Might save me re-lidding troubles them..
Other thing - I don't have an option to set different voltages to different cores on my Prime z370-A...

metadist wrote:

Other thing - I don't have an option to set different voltages to different cores on my Prime z370-A...

I am not aware of any motherboard that allows per core voltage control if you use a manual voltage, possible the "Adaptive" or "Offset voltage" control would control a per core voltage, though.

However a possible option is to set a per core multiplier and have the core that run hotter set to a lower multiple. E.g., let's say if cores 4 and 5 are always showing that these 2 cores run much hotter than the rest of the cores when you have a voltage set manually, you can set a per core multiplier of :

Core 0 x 48
Core 1 x 48
Core 2 x 48
Core 3 x 45
Core 4 x 45
Core 5 x 48

This is just an example, but you might need to experiment with this including core voltage. You could see how a manual voltage of let's say v1.25 to v1.30 affects those 2 cores in a benchmark. Then try an Adaptive voltage setting etc. and see how which setting affects the cores temps in a benchmark under load.

As and end note, a build I did last year with a Maximus VIII Ranger mobo running an i7 6700 non K CPU one of the 4 cores ran about 20 deg hotter than the 3 other cores. This was pretty well at all times, especially when a little load was put on the CPU. I was tempted to do a delid just to satisfy my curiosity, but since it wasn't a K model CPU I decided to not go ahead with it. SO whether it was due to an uneven layer of heatsink compound on the CPU die or something else that was causing this heat differential with a single core, I will never know.

It goes to show that it can and it does happen. The thing that matters to me is does it affect the lifespan of that core, which effects the lifespan of the cpu, OR the work it can do under load when power throttling cuts in due to overheating that core, lowering the overall score in a benchmark test etc.

@jologskyblues I take it from what you say is that there was/is an AVERAGE temp variance between all 6 cores, which is normal. There will [always] be variation in temperature between all the cores in a multi-core CPU because the load the OS puts on the CPU varies between each core. I'm guessing you already know that.

However, this thread is about just one or two cores always running hotter by a good margin, than the rest of the cores, e.g. in my case with an i7 6700 one core ran hotter even at idle under no load by a good margin. This is definitely an indication that something is not 100% right with CPU either at the silicon level or something to do with the thermal paste intel uses or its application [air pockets left between the die and CPU lid e.g.].

But I do understand how the delid helped to reduce the temperature of the CPU as you explained, which would effect the temp variation % between all the cores to be less, I'd think.