Renoise 1.9 supports now multicore CPUs. Here is what you can expect from it and what not:
Hyperthreading CPUs of the first HT generation CPU lines are not supported.
They will be treated like single CPUs as our testing results did not show any real performance gains, or even worse: They cause a performance degrease.
Why? HT Cpus are “faked” multicore CPUs. Realtime parallel Audio processing (the way we use the multiple cores) can not really be handled by them.
The i5 and i7 and newer Intel CPU’s with HT technology are much more efficient on this area so these CPU lines are supported.
2 CPUs = 2x performance speedup?
Unfortunately its not that easy. Handling multiple CPUs first costs the engine a bit of performance (you need to take care of the multiple “audio streams”), but this is in overall not very much. The amount of this overhead is visible when enabling/disabling the multicore support in an empty song (not playing back anything).
Then Renoise has to split your song int “independent streams” that the CPUs can then handle separately. In complex songs with a lot of send tracks and devices this limits the sharing capabilities a bit, which means that the performance is not very well balanced.
In practice this means that the speedup will be something like 1.2x to 1.6x, (on OS X even up to 1.8x) per CPU, depending on which song you are running.
Multicore support in VSTs:
Some VSTs already provide multicore support (like Kontakt), so Renoise wont be able to process such VSTs faster than before.
Taskmanager shows the same CPU usage as before!
This is not because all we did is faking the Renoise CPU meter 
, but because the overall application performance does not increase. Let my try to explain why:
Lets say you have 2 CPUs and run a song in Renoise 1.8:
When the CPU meter showed 100 percent in Renoise, Renoise only used 100 percent of !one! CPU. The other CPU idled around then but you could not
go beyond the 100 percent in Renoise. Taskmanager would have shown an overall CPU amount of 50 percent then, as your other CPU had nothing to do at all.
If you load this song in Renoise 1.9, the CPU meter in Renoise will show something around 60 percent, Taskmanager will still show 50 percent.
The overall performance is still the same, but you now have 40 (100 - 60) percent free for more FX and stuff in Renoise!
