How many in-order cores could one fit on a die?

I was on a receiving end of trying to make Niagara work (the second one, with multiple FPUs). In Java, which is supposed to be its natural habitat.

It never worked well, garbage collection was slow because even the "parallel" GC in Sun JVM was not quite parallel and the sequential parts were causing huge delays because the single-threaded execution was super-slow.

Later, we tried to use Tilera CPUs (massively parallel CPUs with 32 cores) for networking software, and it ALSO failed miserably. Turns out that occasional serialized code just overwhelms everything. I still have a MikroTik Tilera-based router from that experiment, I'm using it for my home network.