coroutines in MCL

[ban@ifi.unizh.ch (Bela Ban)]

Has anyone implemented the concept of co-routines in MCL ?
Co-routines are processes that can transfer control to other
processes and, when control is returned, proceed from the point after the
control was transferred.
One would have to save the registers in order to do this.
Is there a way to access the data and address registers from MCL ?
If not, is there a way to write assembler statements in a Lisp
function (like the asm statement in C++) ?
I think that the lisp background process was implemented as
a co-routine, is this true ?
Cheers, Bela