[aWidebrant]

Putting a CPU core in your hardware accelerator seems more useful when it's stuck on the wrong side of a memory bottleneck. That way, you could run longer programs in local accelerator memory before you have to take the hit of communicating with the rest of the system.

Apple's M1 seems designed to give all types of cores equally fast access to the same memory pool. At that point, it might make more sense to make your accelerator cores as simple as possible and program them from the CPU.

I guess what's really not clear to me is why, if you're building your main CPU on ARM, you would pick RISC-V for your programmable accelerators in the same SoC, rather than using one of the smaller ARM cores available.

[socialdemocrat]

It is mentioned in the article. ARM has a much larger and complex instruction set which means you need to have a larger silicon real-estate. E.g. for a minimal core with similar features, cache etc, a RISC-V CPU would take half the die space of ARM. Half the size is 4x cheaper, as cost grows exponentially with die area.