Turning off a core in a Module

[satyamdubey]

First up, I do not have an AMD system around to tinker with but I've seen posts from very informed people that in an AMD Bully/Vishy module, you can turn on core off and allow the other to utilize the shared resurces (decoder and fpu are the two i know of).

What intrigues me is, what is actually happening at the machine level. How doe BIOS switch off a core, what is the logic that is implemented at the machine code (?? is that what its called?)/low level language that accomplishes that. how is it physically translated?

Is there no voltage going into the switched off core?

thanks a lot
there is always so much to learn from you guys

-satyam

 

[satyamdubey]

anybody?

 

[bigj1985]

I'm not absolutely positive as I have never attempted to disable cores on my wifes AMD system. But I'm pretty sure you cannot disable only a single core per se. Since the cores are seperates in pairs of 2 known a "modules" and there are 4 modules total. I believe you can only disable a single "module" at a time. Which means you can only disable 2 cores at a time.

 

[satyamdubey]

Well Sarinaide posted that he has tested vishera modules and you can infact absolutely isolate every single core in a module.

It is possible that i may have understood him wrong. but even if it is just disabling the modules that is possible, whats happening at hardware level that accomplishes that.

Is it somehow available but just masked so that the OS cannot see it?