Any documentation on SMP with Z-80s?

I've got a bunch of Z-80's that I'd like to dedicate to a fairly simple, but
fairly parallel, real-time algorithm and I was wondering if there's any
public documentation available for doing SMP with them.  Yes, I could use a
PC or three but the algorithm is simple but hard real-time and I think
something like a Z-80 would suffice.  I've chosen the Z-80 simply because
I'm familiar with it, but I'd accept recommendations for other,
not-to-expensive uC/uP as well.  This is a one-off, partially work,
partially hobby project so there are different cost-considerations than in a
production unit.

    TIA
        Norm