4 Cores available, Only 2 seem to be utilized


I have a Quad-Core (Intel Q6600) and while I can select “4 CPUs” in Renoise in the CPU-Dropdown-Menu, only 2 seem to get used at all. When Renoise CPU-usage-display is at 100% (and hence sound starts to crackle), Taskmanager/Speedfan only show exactly 50% CPU usage. Attached is a screenshot of this behaviour. I hope this can be fixed so that all cores will be used by Renoise in the future, because this is why I got the Quad-Core :)

P.S.: I am running latest Renoise version (I suppose):
Renoise V1.9.1
Release date: Jan 2008

P.S.2: Just to make sure Speedfan/Taskmanager are correct, I started Prime95 (CPU burn-in test) 4 times, and then Speedfan/Taskmanager show first 25%, 50%, 75% and 100% when I open the 4th instance of Prime95, so their display is absolutely correct and it´s definetely Renoise which is simply using only 2 cores unfortunately.

Are you using lots of synthedit plugins? These do not support multicore (they do randomly crash when trying to), thus get calced on one processor only. This would explain why only one CPU is at 100% in your example.

Would also be great if you could post/upload your example song, so that we all can take a look at this…

No Synthedit Plugins at all. It´s Korg M1/Wavestation mainly (with up to 5 instances layered for one sound), with Sylenth1 and a few large DSP chains on the effect-channels of each track. Only serious stuff really. As for uploading the song I can´t currently do that because of copyright issues as the song will get released through the label I am signed to later on.

As for the CPU-Usage and the argument only 1 kernel used full, it´s fluctuating all the time between kernels. This is just the time of the screenshot there that this 1 kernel seemed fully used. It really spreads it between all kernels pretty evenly and the load for each kernel fluctuates all the time (I could create a AVI if needed).

P.S.: No crashes at all so far, rock-stable even during the 100% usage phases, not a single crash, good work:)

If you can not upload the song, let my try to explain how the multicore stuff works in Renoise, so you get a better picture of whats happening - what works and what not. Its not that you can simply say that you get a 4x speedup with 4 cores against one core - with no audio application:

Its enough that only one core is at 100% to make Renoises CPU usage 100%. Renoise splits down the tracks that are currently running in your example into “4 units”, which then get assigned to one CPU each. If now one of these units reaches its limit (is above 100%), but the other cores/units are already done with their processing, you end up in simply waiting for the one core that overloads.

This means, as soon as you play back for example one synth that uses more than one core can handle (this one synth plus its tracks its playing on), you end up in 100% audio usage.

We can not “spread” one single instrument to all 4 cores, we only can split up tracks. Only the VSTi itself could do this (Kontakt for example will do).

So does one of the Korg M1/Wavestation instrument produce this overload, even when playing it back alone (without the other instruments)?

Also see our MultiCore FAQ please.

I understand what you are saying. If one VSTi (or in my case most likely several instances of it that I load through EnergyXT and which Renoise regards as one VSTi I guess) produces a CPU load worth using one FULL kernel, then audio will stutter because Renoise can´t spread that to more kernels. But it spreads the other VSTi´s, even if they don´t support multi-core themself, at least to the next “available” kernel. Is this correct?

Yes, exactly.

But if you have a song where you think Renoise still behaves wrong, upload it please so that we can take a look at this.

http://www.kvraudio.com/get/2500.html - scroll down

It´s one instance of Sylenth1 which takes 0,5% CPU exactly;) Running the Q6600 at 4x4gHz watercooled.

Thanks for the fast help Taktik, I already thought something that it works that way, but good to see it confirmed.

and again a good reason to not give away the rights of your music…

I own the rights of the music since I composing it:) I just want noone to copy it before I release it, since I earn a living from my music. I am sure you understand.

Highly understandable. Muting out other tracks won’t work if only one core causes 100% overload on one vsti that causes crackles. But there is still the option of Render To Sample or Freezing by using a freeze plugin.
I guess that will have to do then in this case.

4x4Ghz and you managed to max it out? i thought with Q6600 (even not overlocked) its very hard to do that :)