I am currently designing and implementing a real time operating system. The OS itself is purely coded in assembly whereby the tasks it should be able to handle are coded in C (can handle up to a maximum of 8 tasks).

The OS switches from one task to another (round-robin fashion) when the Timer2 interrupts a number of times. Each time an interrupt occurs I am pushing the following registers to stack; DPL, DPH, ACC and PSW (PCL and PCH are pushed automatically when an interrupt occurs). Are those registers adequate for smooth operation or should I push more 'vital registers' to stack assuming no external (serial) interrupts occur?