that have Custom Extensions, come under the "vendor/arch-id read only
is a declaration of having no Custom Extensions" fall-back category)
+So to summarise:
+
+* The consequences of not tackling this are severe: the RISC-V Foundation
+ cannot take a back seat. If it does, clear historical precedent shows
+ 100% what the outcome will be (1).
+* The retro-fitting cost onto existing implementations (even though the
+ specification has not been finalised) is negligeable
+ (changes to words in the specification);
+* The benefits are clear (pain-free transition path for vendors to safely
+ upgrade over time; no fights over Custom opcode space; no hassle for
+ software toolchain; no hassle for GNU/Linux Distros)
+* The implementation details are clear (and problem-free except for
+ vendors who insist on deploying dozens of conflicting Custom Extensions:
+ an extreme unlikely outlier).
+
# Conversation Exerpts
The following conversation exerpts are taken from the ISA-dev discussion