Yes, Cubase will “use” all the cores.
On these PC DAW choices, Cubase is second only to Reaper in its ability to scale across processors. Sonar is the worst at this. Studio One is in second to last place.
On Mac, this changes to somewhat of a tie between Logic and Cubase (Logic winning most of the time), Reaper still taking first place. Studio One last in place.
This was sort of a quest I was on last year. I recreated a very large project in all these DAWs.
Even though Reaper won, I just couldn’t use it as my main DAW for nitpicky reasons.
Anyway, the real answer has to do with how you use your DAW.
For example, in Sonar, if you use many live effects on the stereo bus – what it considers a “serial signal path” – it will only process what can fit in ONE CORE. It can’t split that up across the other cores, free as they may be.
Reaper, in this same example will do it perfectly due to how it does its “audio buffer scheduling / slicing.”
Back to Cubase: I’m not sure, but it seems to do better than Sonar in this use-case but not as well as Reaper. So I’m not sure how much it suffered from this limitation that’s confirmed in Sonar.
What’s not a “serial signal path” from the DAW’s standpoint? Well, that is probably unique to each DAW. For Sonar it’s been confirmed that any VST instruments on individual tracks, escape the serial path and are now considered on “parallel signal paths” and then, in Sonar, can use other free cores.
How is this in Cubase? I was never able to really get an accurate answer.
One thing is probably true: while there are confirmed cases (Sonar) of DAWs, in certain use-cases, that can’t muli-core scale, is the reverse true? Are there DAWs in certain use-cases that can only use part of a core and then seek out an unused core to jump to? I really, really doubt this. So…
To err on the side of caution, I think it would be better to have few, faster cores than more slower cores – all things being equal. Obviously, in situations where the sheer number of cores provides more, total processing capacity, it has the potential to be a more capable machine.