Is there some really interesting documentation available for these
chips and maybe some microcode for some really simple task?
Read the online Book.
I have planned to do a Bitslice design but I have never come up with a
simple to
decode instruction set. From what little I have looked at the 2901's you
still need
TTL to interface to the real world, like input/output and address latches.
Note a PDP-11 stretched to 20 bits might be a GOOD 2901 design.
{OP}{Byte:MODE}{R0-15}{byte:mode}{R0-15}