[slededit]

The common refrain I hear from hardware guys is that the uncore is the hardest part by far. The bulk of design time is spent connecting multiple cores together. Great single thread perf doesn't imply an easy path to multicore.

[macintux]

Still, the A-series multicore benchmarks have been pretty impressive as well.

[slededit]

The problems arise when you start getting into double digit core counts. At 4 you can make pretty reasonable MUXes still. Above that you need to start making serious trade-offs to either Fmax or latency.