The lack of performance boost I think is caused for a few reasons: The extreme amount of optimization on both the architecture makers and compiler writers. They

The lack of performance boost I think is caused for a few reasons: The extreme amount of optimization on both the architecture makers and compiler writers. They hyper-optimized to the architectures they had, so giving them general registers support didn't buy you much. As for why it was lambasted for its lack of general purpose registers? General-purpose registers make writing compiler back-ends cleaner and reduces the need for some stubs.