Thread by @ErrataRob

1/ Back around 1990, there was a "RISC" revolution, a useful tradeoff that made sense given the Moore's Law state of technology at the time. By 1998, it was obsolete, and technology has evolved past it being a meaningful difference. Yet, the term refuses to die.

2/ I mention this because of this article on YCombinator. It's painful to read. It argues against ignorant RISC vs. CISC misconceptions, then argues for new ignorant misconceptions. It's a train wreck.
reveried.com/article/arm-pr…

3/ ARM processors aren't more power efficient than Intel processors. A Raspberry Pi (ARM Cortex-A53) consumes more power at idle and at full load than an equivalent Intel computer.
up-board.org/up/specificati…

4/ They aren't less power efficient, either. The reason is the Raspberry Pi's CPU is fabricated at 40nm node, which uses more power, while the Intel Atom processor is fabricated at the more power efficient 22nm node.

5/ ARM is used in cell phones not because they are more power efficient, but because ARM targeted the cell phone market and Intel didn't. By the time Intel decided to compete in that market with the Atom processor, it was too late.

6/ ARM does have a flexibility advantage. They sell CPU designs that can be incorporated in other chips. Intel has an inherent disadvantage that it's not easy to incorporate their Atom cores with other functionality.

7/ On the other hand, Intel has an advantage at the high-end fast processors, because it can invest in the enormous engineering costs needed to gain a marginal speed improvement over its competitors.

8/ But as Moore's wheel turns, Intel's ability to outdistance competitors on speed has been shrinking, so now the AMD x86 Ryzen/Epyc CPUs are close "enough" to Intel in speed, as is Apple's chip at the heart of the iPhone.

9/ Anyway, the differences in both speed and efficiency have to do with a lot of things, but none of them is "RISC vs. CISC". That difference died over 2 decades ago. It dominates the discussion because it's a meme, not because it's rational.

10/ As for that scene in Hackers where "RISC is good -- it'll change everything", well, it did. The P6 chip in question, also known as the Pentium Pro, took some useful tricks from RISC, tricks that all processors use, regardless of instruction set.

11/ A fast ARM processor designed to compete with fast Intel processors have roughly the same number of pipeline stages to fetch and decode instructions into micro-ops as an Intel architecture.