A noob question about CPU usage on Lion.

[east85]

After doing some quick search through the forums I couldn't find an explanation but I am wondering why it is that the CPU can essentially run at 100% while % idle lingers at around 50.

 

[GGJstudios]

After doing some quick search through the forums I couldn't find an explanation but I am wondering why it is that the CPU can essentially run at 100% while % idle lingers at around 50.

If you have two cores, it's capable of 100% for each, for a total of 200%.

 

[east85]

If you have two cores, it's capable of 100% for each, for a total of 200%.

Oh okay, I do have two cores. I was just wondering because while doing some intensive tasks it seemed like it would never break that 100% threshold. Is that normal? Should I run a diagnostics tool? Thanks for clearing up my initial question!

 

[Mal]

Not entirely sure what you're asking, but the processor usage is not measured from 0-100%. Each processor in modern Macs has a virtual core for each physical core, so a dual-core processor will present itself to the system as having four core, each of which can be 100% utilized, so at any given time, you could see up to 400% processor utilization. On a quad-core Mac, it's double that even. The high end Mac Pro can actually have 2400% processor utilization if you manage to max it out. This is the source of most of the confusion I've seen from other about this type of thing, so hopefully it's helpful.

EDIT: Heh, I was too slow. I'll work on this question now though:

Oh okay, I do have two cores. I was just wondering because while doing some intensive tasks it seemed like it would never break that 100% threshold. Is that normal? Should I run a diagnostics tool? Thanks for clearing up my initial question!

Many applications can't use multiple processor cores, so it's normal that they might max out one while the other remains idle.

jW