Despite how simple and limited the 6502 is, it's always interesting to see this almost 50-year-old architecture being stretched to new limits. 6502 cores are still found in some SoCs aimed at the ultra-low-cost high-volume market.
What's the reason behind that? Probably just keeping existing, working designs and thus saving R&D costs? Sounds like beating a 10 cent risc-v core would be hard.
Edit: When I first read your comment I had to chuckle a bit, because I got the image of a multicore SoC with 6502 6502 cores. That would be a fun project for my FPGA hmmmmmmmm ...
If your chip needs very basic processing, and you're going to sell it for less than a cent per chip, you need your core to be basically free.
Sure RISC-V is very inexpensive, but for parts like these risc is massive overkill and as a modern core, you'll be spending a lot of die area on a core that should really be an ASIC, but designing an ASIC is expensive so you can just slap a 6502 in that bad boy and call it a day.
On the other end of the scale, you'd be surprised to learn that many chips you don't ever interface with as a user contain even ARM cores. These are usually ASICs in high-end products.
You seem to underestimate how small a RISC-V core can be.
Take a look at SERV.
6502 has 3510 transistors. SERV at CMOS occupies 2.1kGE.
SERV is smaller than 6502.
And that count doesn't include SERV's register file.
In that case, I'd rather have RISC-V's programming model.
SERV is smaller.
I have the 16 bit successor, the 65816, on a variable speed expansion card in my Apple 2. I run it in 8 bit mode most of the time mostly because it works and most library code is 8 bit.
At those speeds, the chip is fast! Especially when one considers the simple model: ram clocked 1:1 with the cpu. In my case, I can run code over the 1Mhz bus, essentially turning most multi cycle ops into a single bus cycle per memory fetch.
Or, the card has a megabyte of RAM and that runs at CPU speed. (0.15 to 16 Mhz) When doing that, it is fast enough to run large programs, written in higher level languages, at a useful speed. Of course Assembly language is crazy fast.
It is a pretty fun environment to hack around in.