It's less than you would think. Despite having offerings in about every IP block segment about the only ARM IP blocks that get heavy use are the pieces that have some other ecosystem thing going on. PL011 uarts are de facto required for some initial consoles. Mali GPUs were being sold in what was frankly a move that needed some anti-trust scrutiny (ARM saw Apple taking the piss out of IMG and decided to go in for the kill by offering CPUs+GPU for cheaper than CPUs on their own, overnight destroying IMG's market). Beyond that it's easier to not pay ARM for their IP. NoC fabrics and IP blocks that touch pads are better coming relatively straight from the foundry. Simple serial controllers are essentially commodities at this point. Etc.
So RISC-V really only needs to focus on CPU cores to be an existential threat to ARM.
At this point their biggest most is probably the patents on AMBA specs, but if they tried hard to enforce those the industry would switch to something like TileLink in a relative heartbeat.
I am giving RISC-V 5 to 10 years to catch up in my estimates. I think that is fair. The momentum behind RISC-V is massive and even then I am not saying it is fast.
5 years is a flash in chip design. Initial design to tape-out is 3 years at the leading edge if you're really good.
Maybe in 5-10 years, RISC-V gains share in initial designs, but the semiconductor design process is loooong.
And if you're going to talk about Microcontrollers and simpler chips, keep in mind we had a bunch of other RISC architectures a decade ago that all lost to Cortex-M for simplicity/cost reasons (RIP MIPS).
I think RISC-V eats ARM's lunch at the low end across the board over the next 5 years. Financially that is okay in the near term for ARM as the major profits are all in the high end designs.
But all that will be left in a few years is the high end areas and where there is a lot of lock in to the ISA.
It isn't yet clear when RISC-V will be ready to compete at the highest end of things, but that is where Jim Keller comes in.
RISC-V is a classic market disruptor for ARM, just as ARM was a disruptor to Intel.
