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> 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 ...



10c per part is incredibly high depending on how low-cost we're talking.

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.


>but for parts like these risc is massive overkill

You seem to underestimate how small a RISC-V core can be.

Take a look at SERV.


The area of just the register file (even for rv32e) is higher area than the survivors of the 8 bit ucontrollers.


16 registers * 32 bits * 4 transistors / cell = 2k transistors just for storing the bits alone, and that's not including the decoding and read/write circuitry.


There is no need to do weird math, as we know the actual numbers.

6502 has 3510 transistors. SERV at CMOS occupies 2.1kGE.

SERV is smaller than 6502.


Gate Elements are multiple transistors.

And that count doesn't include SERV's register file.


So you're saying they'd end up in the same ballpark?

In that case, I'd rather have RISC-V's programming model.


More like about half the size. And probably running at about 10x the IPC of SERV.


Not true for SERV vs 6502.

SERV is smaller.


There’s also the cost of rewriting (yes, from assembler) all the existing code. And don’t forget QA.


Go on!


A lot of cheap USB1/2 widgets are actually a 6800 core. It's crazy how these old CPUs have stuck around for so long




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