POWER is basically only top of the line though, other than the relatively rare NXP QorIQ chips that were used in e.g. AmigaOne stuff.
Most of the hype for RISC-V seems to be in tiny embedded stuff (e.g. WD's disk controllers) and academia (naturally). SiFive has finally made an out-of-order core, but I don't really see the market for big unix-capable RISC-V. RISC-V is really a royalty-free "MIPS in a trenchcoat", so expect it to be used where MIPS is used now.
ARM is everywhere, from smartphones (unfortunately Qualcomm dominance, but Apple is kicking ass in performance) to AWS EC2 (in-house silicon!) to massive HPC clusters (Fujitsu A64FX is impressive, they use HBM2 RAM (!) to make a SIMD-capable CPU into something almost GPU-like in a way).
AWS has basically ensured that ARM is the next ISA for servers :P
I'm certainly not downplaying ARM's domination in general, but don't take this bit for granted:
> AWS has basically ensured that ARM is the next ISA for servers :P
These hyper-scalers (inc. Microsoft, Google, Alibaba...) will take a little bit of everything, because they generally can always find cookie-cutter workloads impeccably suited to any architecture, but also as industrial diversification, for R&D, etc. Like AMD, the presence of some ARM CPUs in the biggest datacenters says little about market forces, what matters is how many actual FLOPS are effectively handled by each vendor. I'm positive Intel still has the lion share, and the inflexion point in favor of AMD (nearest competitor) would be 2023 at best, more likely 2025-26 assuming Intel eventually catches up in price/perf/W.
A reasonably heterogenous infrastructure is very good when you're an order of magnitude bigger than entire datacenters, or so I hear.
I share your concern that RISC-V is currently largely confined to the MIPS space; and indeed it's a totally different ballgame to break into ARM's space, let alone x86 (but I don't see why RISC-V would seek the latter, especially considering POWER is up there).
Most of the hype for RISC-V seems to be in tiny embedded stuff (e.g. WD's disk controllers) and academia (naturally). SiFive has finally made an out-of-order core, but I don't really see the market for big unix-capable RISC-V. RISC-V is really a royalty-free "MIPS in a trenchcoat", so expect it to be used where MIPS is used now.
ARM is everywhere, from smartphones (unfortunately Qualcomm dominance, but Apple is kicking ass in performance) to AWS EC2 (in-house silicon!) to massive HPC clusters (Fujitsu A64FX is impressive, they use HBM2 RAM (!) to make a SIMD-capable CPU into something almost GPU-like in a way). AWS has basically ensured that ARM is the next ISA for servers :P