Interestingly, it appears based on https://en.wikipedia.org/wiki/Intel_iAPX_432#The_project's_f... the procedure call instruction was a heavyweight thing designed to maximise features and it could branch much more quickly - but their compilers didn't handle that out of the box.
> The iAPX 432 failure could best be summed up by a meeting of Intel marketroids and Tandem engineers who wanted to use the chip in their next generation machine, after the slides, the senior engineer asked: “How long does it take to execute a procedure call?”
> The presenter looked it up. “Two hundred and fifty microseconds.”
> Tom immediately walked out, followed by the majority of the Tandem software department. The presenter was poleaxed. “What did I say?”
Found in comments to https://www.youtube.com/watch?v=FvmTSpJU-Xc , but I saw it somewhere else, too, I just don't recall where. Doesn't anyone know?