Intel SB/IB CPU idle power - when is "idle" really idle?

[VirtualLarry]

Just curious, I hear all of these good things about SB (and now IB?) in terms of idle power consumption. Basically, power-gating the cores and such.

However, that would seem to me to be a state in which NOTHING is running on your PC, in the background, no network streaming, etc.

Is this true?

If I have a HTPC, and am running internet radio in the background, but mute it, and keep it streaming, will I still have low idle power? Or not?

Does the CPU wake up for X nanoseconds to compute what it has to for the internet radio, stream the data to the sound device's buffer, etc., and then enter power-down idle mode, until the next timeslice timer tick? Or does it stay "awake", at some minimal power draw higher than idle all of the time?

 

[IntelUser2000]

Does the CPU wake up for X nanoseconds to compute what it has to for the internet radio, stream the data to the sound device's buffer, etc., and then enter power-down idle mode, until the next timeslice timer tick? Or does it stay "awake", at some minimal power draw higher than idle all of the time?

Yes, that's exactly how it works. More than just the OS timer though, perhaps the HD Audio codec and Network needs to wake it up once in a while. If the gap between interrupts are too small it may never get to the lowest power states and stay in the higher ones.

 

[ShintaiDK]

Idle is also when you just listen to MP3 etc. Simply because the task is so low demanding.

Also its power on demand, try open CPU-Z and note how the clock goes depending on what you do. You would note that almost all the time on your windows desktop it idles. Even when you read webpages.

Its either idle or not. But can variate between idle up to full load. Then and turbo beyond that in essentially the same method. Just reversed.

 

[VirtualLarry]

Idle is also when you just listen to MP3 etc. Simply because the task is so low demanding.

Also its power on demand, try open CPU-Z and note how the clock goes depending on what you do. You would note that almost all the time on your windows desktop it idles. Even when you read webpages.

Its either idle or not. But can variate between idle up to full load. Then and turbo beyond that in essentially the same method. Just reversed.

I'm not talking about full-on idle. (Lowest Speedstep setting for multi/voltage, but still fully-powered CPU cores.) I was speaking more of the core power-down idle, that's where the real idle power savings happens.

I was wondering if the CPU could enter the core power-down idle states, with something like internet radio running in the background.

Certainly, though, at the very least, it should run at the fully-powered idle speedstep state.

 

[Abwx]

Let s say when the Task Manager show below 1% CPU usage......
For a modern quad core , that would still be as powerfull
as a pentium pro 200 at full speed....

 

[ShintaiDK]

I'm not talking about full-on idle. (Lowest Speedstep setting for multi/voltage, but still fully-powered CPU cores.) I was speaking more of the core power-down idle, that's where the real idle power savings happens.

I was wondering if the CPU could enter the core power-down idle states, with something like internet radio running in the background.

Certainly, though, at the very least, it should run at the fully-powered idle speedstep state.

I´m not sure what you talk about then. Because next step would be sleep modes.

So yes, it can. Even if 1-3 cores are gated. Use CPU-Z and see.

 

[ShintaiDK]

Let s say when the Task Manager show below 1% CPU usage......
For a modern quad core , that would still be as powerfull
as a pentium pro 200 at full speed....

Exactly.

 

[AkumaX]

On a (somewhat) related note, is there a way to force idle to clock lower than normal (16x mult)? I noticed on one of the Real Temp + Prime 95 tests, they were able to bring it down to 8x.

 

[ShintaiDK]

On a (somewhat) related note, is there a way to force idle to clock lower than normal (16x mult)? I noticed on one of the Real Temp + Prime 95 tests, they were able to bring it down to 8x.

I dont think so. Where did you see that? Perhaps it was different CPUs.

Lynnfield idled at 1200Mhz if I recall right. Sandy and Ivy at 1600Mhz. Its basicly the number where it makes no sense to go lower in terms of saved wattage.