If you were to do what I hope to get around to doing someday, namely to modify ULTRAMON51 to use an external UART, then you could build a board that lives on an 805x socket.

Of course it would have some limitations (One of my ICE systems (not for the 805x, though) has a tentacle that is terminated in any of several modules that plug into DIP or PLCC sockets compatible with standard sockets, PLCC68, PGA64, PLCC44, DIP64, DIP48, etc. This setup contains a separate processor that looks over the shoulder of the target, and stops the target when necessary to perform one or another operation, thereby preserving the state of the target MCU.

I figure that one day, I'll build a little module that plugs into the DIP-40 8052 site and uses an external UART to communicate with the console, thereby leaving the timers and serial ports for use by the application under development. That won't cost much and will do most of what one needs. You can be pretty fancy with the thing, i.e, you can map memory, selectively, into code and data space, or both, thereby making some RAM-based code space available and even writeable. A PLD of some sort would make all that pretty easy, though probably unnecessary.

RE