C1E, C3, C6, EIST, Speedstep, Turbo Boost, Core parking

I asked one of my support guys to write a why there is issues with Turbo etc.

The issues showing back here when Turbo Mode is active are random drop outs at lower latency and also plugins causing drop outs. Firewire Devices seem to be far more interrupted by the Turbo State changes. The issues are intermittent due to how Turbo Mode doesn't always change the Base Clock Frequency which alters the Ram frequency and it doesn’t always turn off cores. Sometimes it is fine frequency adjustments that raises the clock speed less than 100 MHz which also raises the ram speed. If you launch CPUID you can watch this activity real time. What is for certain is the C- State or Frequency changes happen via Communication to the ACPI which is on the SMBus and Bios. This communication is on the PCI Bus and at a very high Priority. Since audio requires constant CPU communication at a high priority especially at lower latency this will cause interrupts in the audio especially at lower latency or when plugins have some delay compensation affecting the audio.
 
The Turbo Mode will also gate off cores based on what the Host is sending for threads which was the real purpose for Turbo Mode. This works great with video games and Business applications. However for audio it's a nightmare. Remember your audio host program might multi-thread great but that doesn’t mean your plugins do. Plugins and Plugin cards often only single thread which will send high priority commands to one or 2 cores. All of the Turbo Mode moderation is at the CPU. If the CPU determines that the data is only single threaded it's going to start shutting down cores for performance sake. When this happens cache may be wiped which is part of the C state process which can cause current audio data that other cores were using to be wiped out. This process forces the CPU to restart the thread from the beginning which will show up as an audio drop out since audio requires the stream to be constant. Hence why this shows up intermittently and is much more common at low latency.
 
Remember all of this communication is traveling along the PCI Bus taking high priority. Other Devices requesting CPU time are pushed to cache state while this is going on. Also this communication is taking bandwidth that PCI bus devices are using. This really shows up on Firewire Audio devices due to how those are designed and laptops due to resource stacking and Device ID prioritizing to squeeze as much data through a limited highway as possible.
 
Once again all of this is intermittent due to what you are doing, what hardware/plugins you are using, and what latency you are running. You might be fine for 1 session and then have nightmares while mixing. Leaving Turbo Mode active is putting allot of possible failure points into your workflow and will cause issues that may seem like they are due to other factors but are really due to the C state changes and the PCI Bus activity that is occurring from the Turbo Mode and EIST.
 
There is allot more to what is going on in the Background on the current hardware besides this due to the architecture that will also exacerbate this issue more but that is a much longer discussion.  
Eric

Thanks for the info!
 
Can you tell me how to turn off core parking in Win7 64 bit, and Sonar 8.5.2 64 bit?
 
My Win7 meters for the i7 920 CPU show all 8 cores running at about 30%. The overall system is at about 33%.
 
But inside Sonar, I load the large transport bar which shows all cores running about 30% except the first one which is running around 70%. If I push the system I can get it to 80% and dropouts occur, but the other 7 cores are still at 30%. And there is no spike in the Win7 meters either.
 
I'm thinking somehow Sonar is mostly using core 1 and when that taps out, doesn't go to the other ones. I would love for it to use all 8 at once. Do you know if this is possible?
 
Thanks,
 
 
 
 

Scott / Eric ...

many thanks for taking the time and putting out your "condensed" version on all this.  It certainly is fascinating to read how the gurus are going about solving one problem (power consumption / heat) while creating new ones.  As always, it's the minority groups (e.g. us DAW users) that suffer the most in the process.  Pity nobody thinks about creating a DAW-only OS, with DAW-only specific processors/chips.  The major DAW software, chipmakers and OS companies could all get together, just like the instrument makers did with MIDI back then.

Maybe, one day ...

John


Well I asked for reasons and you sure as heck gave them. I will need some time to digest all this. In the meantime thanks for doing this Scott.

My pleasure John! there is much more Eric or i could write but i ran out of time and really much more past what we posted would become too long a read.
i had wanted to mention wave Rt and how its supposed to get us even closer to real system time by accessing the hardware layer more directly.
but thats for another day.
 
When challenged i dont normally have the time to write essays ( as it was i was in here on Sat finishing it, when i was supposed to be working on my wifes website :-)  ) i just could not get it done during a normal work week. too many interuptions.
 
i also left off that settings vary with motherboards.
that turning off C1E stops a good amount of it but your cpu can still throttle up/down with eist or by leaving turbo boost on.
turbo cant function completely (cant turn off cores since C1e is off) but can change some things and again it varies by bios and how the manufacturer impliments it and ACPI.
 
  
 

Really great Stuff! I have a new setup and still am "confused" about some of the BIOS settings. This helps and it's just great that you took the time and effort to explain all this so fully.
I have the Asus P6T SE which has the AI tweaker crap. I have turned off things I was pretty sure of. Asus should write a manual just about their BIOS settings. I have 6GB Triple Channel Corsair XMS3 1600. It's running at 1066 according to the Bios. On the Asus website forums it says to leave it like that? Why did I buy 1600 if I am going to run it at 1066? But I am not sure what to edit to get "normal" operation from this MB. If that's even possible.
Thanks for the fabulous reference info!
Frank

All power saving should be turned off including turbo yes.

... only single thread which will send high priority commands to one or 2 cores ...
... it's going to start shutting down cores for performance sake ...
... cache may be wiped which is part of the C state process which can cause current audio data that other cores were using to be wiped out ...
... This process forces the CPU to restart the thread from the beginning ...
... all of this communication is traveling along the PCI Bus ...

???

Bill B.

As posted in my other thread, thanks, Scott! Information (partially, still working on it) assimilated and much appreciated.

My current DAW, built before the i7's were out I think, is (don't laugh) AMD-based (Phenom 9850). Is there any equivalent to all this in an AMD-based system I should be looking into?

I asked Asus support about that; and when they said it could throttle down the system I left it strictly alone (default: not enabled). Also haven't messed with AI overclocking ("auto") in the BIOS.

Not that I'm anxious to overclock this system; it's been quite stable so far since I got the right RAM in it. I leave overclocking to experts like yourself.
Since I don't have CPU spikes like others have reported I guessed that if there was an equivalent in the AMD BIOS it wasn't enabled by default (or isn't causing trouble); but it doesn't hurt to ask.
Thanks again, Scott.