The 5nm vs 7nm vs 10nm vs whatever nm narrative is highly reminiscent that of clock rate flame wars raging in the tech bubble over a decade ago. Back in the early aughts, when the great engineering was still a thing, alternative CPU designs (DEC Alpha 21264, MIPS 10k/12k, PA RISC, POWER and later UltraSPARC designs) were consistently outperforming any x86 design by at least an order of magnitude or more whilst being clocked at 30% to 50% less of the x68 designs, especially in FP operations. The alternative designs explored and utilised wider and deeper pipelines, bigger L1 caches and various optimisations across the entire CPU arch. Every alternative CPU design had something unique to offer, and that was a great thing to read about and study.
The commoditisation of the PC hardware has driven great CPU designs into an extinction. Heck, even Oracle, that are now in the business of litigation for fun and a massive profit, with its prodigious cash war chest has discontinued the UltraSPARC architecture due to it requiring extraordinary investments on multiple fronts. PC users have long been forced to be content with whatever bone the CPU architecture coloniser would throw at them. There appears to be a resurgence of the great engineering with M1, and, hopefully, that will lead to more of the thoughtful engineering in medium to long term.
M1 is fast due to: a solid, single vision of what a modern CPU should be like, continuous investment into R&D over an extended period of time, a well concerted effort of the engineering, design ideas reuse across multiple product lines, supply chain management, and, of course, the manufacturing process. Nanometers do not make for a great CPU design but rather play a supporting role. If the nanometers were so important, the 2017 POWER9 design manufactured at a 14 nm process with a smaller L1 cache would not have been able to outperform any existing x86 design in 2020 in both, single core and multi core (with 25% to 50% lesser number of physical cores) setups? Ryzen 3 has narrowed the gap, but POWER9 still takes the lead and POWER10 is around the corner.
There is a great quote by Michael Mahon, a principal HP architect, in the foreword to the PA RISC 2.0 CPU architecture handbook from 1995:
The purpose of a processor architecture is to define a stable interface which can efficiently couple multiple generations of software investment to successive generations of hardware technology. Stability and efficiency are the goals, and the range of software and hardware technologies expected during the architecture’s life determine the scope for which the goals must be achieved
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Efficiency also has evident value to users, but there is no simple recipe for achieving it. Optimizing architectural efficiency is a complex search in a multidimensional space, involving disciplines ranging from device physics and circuit design at the lower levels of abstraction, to compiler optimizations and application structure at the upper levels.
Because of the inherent complexity of the problem, the design of processor architecture is an iterative, heuristic process which depends upon methodical comparison of alternatives («hill climbing») and upon creative flashes of insight («peak jumping»), guided by engineering judgement and good taste.
To design an efficient processor architecture, then, one needs excellent tools and measurements for accurate comparisons when «hill climbing,» and the most creative and experienced designers for superior «peak jumping.» At HP, this need is met within a cross-functional team of about twenty designers, each with depth in one or more technologies, all guided by a broad vision of the system as a whole.
Well executed holistic approach is the reason why the entry level M1 is fast. We need more of «holistic-ism» in engineering everywhere.