serv VS phison

> Right now, most devices on the market do not support the C extension

This is not true and easily verifiable.

The C extension is defacto required, the only cores that don't support it are special purpose soft cores.

C extension in the smallest IP available core https://github.com/olofk/serv?tab=readme-ov-file

Supports M and C extensions https://github.com/YosysHQ/picorv32

Another sized optimized core with C extension support https://github.com/lowrisc/ibex

C extension in the 10 cent microcontroller https://www.wch-ic.com/products/CH32V003.html

This one should get your goat, it implements as much as it can using only compressed instructions https://github.com/gsmecher/minimax

In short: it works, though the implementation lacks the crystal clarity of FemtoRV32 and PicoRV32. The core is larger than SERV but has higher IPC and (very arguably) a more conventional implementation. The compressed instruction set is easier to expand into regular RV32I instructions than it is to execute directly.

https://github.com/olofk/serv

As for the size advantage: this mattered more when LUTs were precious and when PicoBlaze's competition was either similarly unorthodox (J1 Forth CPU) or several times larger (MicroBlaze). Nowadays, there are very small RISC-V cores like FemtoRV32 Quark or SERV. RISC-V benefits from mainstream open-source tooling and has momentum that's hard to beat.

The RISC-V spec does allow non-trapping behavior and SeRV in particular has non-trapping behavior, which is an important part of how it can fit into 200 4-input LUTs.

https://github.com/olofk/serv#good-to-know

Here's one with a 250MHz 8051: https://github.com/flowswitch/phison/wiki/PS2303

They don't need anything as powerful as ARM (and thus avoid the licensing fees), and it's a very price-sensitive market, so a fast 8051 + accelerator hardware is enough.

No doubt some of the more expensive ones may be ARM-based, but I think the 8051-based ones far outsell them in volume.