Thanks Erik ... that's a neat idea. I'll add it to my ideas bag ... ;-)

Pranav ... it's not my OS ... it is basically SCREEM OS by a smart guy called Barry Kauler. It IS pre-emptive. That costs about 22 bytes of RAM per task. Barry's version has simple round robin scheduling, mine is prioritised - in mine the core of the timer ISR is used to determine what task (if any) should be run, so it is prioritised.

The timer ISR is a bit slow right now, but could be speeded up by rewriting some parts in asm. But I don't think that is the main issue - I think the need for ring buffers is. Otherwise it's like a car with no suspension ... dies quickly ...

I'll post some code samples at my site later, so people can look if they want.