[mshockwave]

> In the end, programs will want probably to stay conservative and will implement only the core ISA

Unlikely, as pointed out in sibling comments the core ISA is too limited. What might prevail is profiles, specifically profiles for application processors like RVA22U64 and RVA23U64, which the latter one makes a lot more sense IMHO.

[sylware]

Come on, what was to be understood is to 'stick to the core ISA' as much as possible.

I had to clarify the obvious: if a program does not need more than a conservative usage of the ISA to run at reasonable speed, no hardcore change to the hardware should be investigated.

Additionnally, the 'adding new machine instructions' fan boys tend to forget about machine instruction fusion (they probably want they names in the extension specifications) which has to be investigated first, and often in such niche cases, it may be not the CPU to think about, but specialized ASIC blocks and/or FPGA.