alt Hacker News> Cortex-M is determinism in hard real-time systems
> or your real-time deadlines are so tight an FPGA would be a better choice
That's why I'd say Cortex-M fits well for a very-very good soft real-time (99.99+%). But for hard real-time (100%) you need an FPGA.
The TI PRUs demonstrate that what you need for hard real time is 2 processors and the ability to completely transfer your register file in a single clock cycle instruction.
This lets your first processor be deterministic hard real time while your second processor is soft real time.
I really wish somebody who makes M-series microcontrollers would get the message already.