Implementing a multitasking OS on top of UNIX

[Craig Robinson]

For my operating systems class we are required to do the following project:

"Groups of three students will design and develop a priority based
multitasking kernel that provides for process control, process
synchronization, and process communication.  The kernel will be developed in
the C programming language and will run on top of the UNIX OS."

This is the exact project specification as stated in our syllabus.  No
more, no less is required.

I have several questions I want to ask the gurus.

1)  In what way would we be able to implement a quantum driven system?   
How can we simulate clock interrupts?

2) In UNIX, what happens *at the CPU level* when a process makes a system
call?  How does the processor know to switch from user to kernel mode?  How
can we simulate this on top of UNIX?

Any other tips anyone can give me would be greatly appreciated, we only have
about 3 more weeks until the due date, and we are all very confused about
exactly how we are going to do this.

Thanks,
Craig
-- 
craig at acns.nwu.edu