> 
> > One last item.  I have in my possession another async mux (M9757) which 
> > I know nothing about.  Can someone identify this for me? 
> 
> M7957 is DZV11 (4 ports, with FIFO)
> M3106 is DZQ11 (4 ports, with FIFO)
> 
> for one of them I've some documentation. If you're interested mail me 
> for details.

Yes, it is an M7957 -- I've transposed digits above.  For now, if someone
could tell me about switchpacks E30 and E2.  From the board etchings, it 
looks like switchpack E30 sets the CSR address, bits 12 down to 3.  
On switchpack E2, it looks like the vector address bits 8 down to 3 are 
on switches 1 through 6.  There are two more switches on E2.  Can someone
confirm this, and tell me the function of the remaining pair of switches?

Bertram, if you (or anyone else) has documentation for either of these 
devices that you wouldn't mind loaning (or parting with), I'd like to
make a driver for this mux, too.

--Carl