Jeffrey S. Sharp wrote:
  What physical format would this project assume?  I can
think of several
 right off hand:
 * A card that emulates CPU/memory and plugs into the (Uni|Q)bus of
   existing machines.
 * A box that sits inside a PDP-11 cabinet and replaces the entire bus and
   all of the cards.
 * A hand-held, battery-powered unit similar to a Game Boy.
 It's the third idea that seems the coolest to me.  Build it low-power
 enough to run on a few batteries.  Give it a front panel with switches and
 LEDs for the processor and emulated peripherals.  Add a serial link (or
 maybe even a Zip disk) for transferring files to/from another computer.
 It would be the ultimate toy.  Just think of all the flavors it could be
 made in. 
So do it with an Agenda, a Linux powered PDA. The project is completeley
open source so all details of the hardware are available. Its CPU is a
64 bit MIPS architecture, it has an LCD screen with touch panel input,
16Mb of flash and iirc 8Mb RAM at a cost of about USD 250.
  -- HBP