Can't reboot after changing cores to use 1 cpu only

So I have done this before on the same machine.

Lowered the processor count in windows down from 40 to 20, so would use only 1 of the 2 cpu’s
Worked fine, hwmonitor reporting 0W on the second CPU.

I switched both cpu back on for some plotting and now when I try to shut one cpu down, windows doesn’t boot anymore, not even in safe mode.
Only option is to boot to command prompt and manually reset the cpu settings.

Anybody got a clue what might be the problem?

I am not sure whether this can be the reason, but my box (2 processors) has some PCI slots assigned to one and some to the other. The same with SATA ports. So, when I remove (physically) the wrong processor, it is as you said - nothing.

I was removing those processor, so knowing which one make that process smooth. However, I am not sure what happens, if you just disable some cores, which processor you are actually targeting. (I even don’t know how to disable those cores like you did.)

Yeah, I think I found how you do it. I just run msconfig / boot advanced options. I don’t see how you can target Proc1 vs Proc2. I think that might be the problem.

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hmm that sounds like a very reasonable explanation, as I just added an expansion card. I was using the method you described via msconfig, so no option to chose cpu.

I will have a look at the manual to see if I can find out how the cpu’s are connected to the pci slots.

Another option would be to select n/2 + 1 as the number of requested cores. That will keep both CPUs at least partially running. However, I don’t know whether you will see much if any power saving (what is the main point of this exercise). I would think that your processors are rather on the old side, as such, not much of power management there, except bringing one down completely.

When you check your mb block diagram, you will see that the South bridge is sitting just on one processor. If that is inactive, then the other one doesn’t have access to anything on that bridge (SATA), and most of PCI slots (most likely also your video card, if you are using one). When you disable that processor sitting on the SB, the other one is basically hosed.

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