Openscad does not multi-thread, so will only use 1 core.
I suspect that it would be a big job to convert to multi-threading, just because otherwise it would have been done long ago. Even the relatively simple step of running a separate UI thread hasn't been done.
Note: This will only split the application of individual (e.g. boolean) operators out into separate threads, not make the operations themselves multi-threaded. The rather non-obvious effect of this is that the maximum speedup tends to be capped at ~35% since the last union operation will still take half of the time and run single-threaded.
I get parallel processing would be akin to a rewrite. I was interested in
understanding if there are any configurable bottlenecks. I'll run over to
github & see what's going on there. Love the community & love the tool.
Really appreciate the feedback!