I pertty much go along with the Ideas given so far. For adding slow I/Os just use serial input of output shift registers that are driven by bit banged I/O. For high speed access to additional I/O your best bet has two forms. Either use a part such as Cygnal with more I/O pins (they offer up to 64 I/Os in a TQFP-100) or use a CPLD that is wired up to either port pins or the external XRAM bus as a memory mapped peripheral. You can use combinations of 'HC138's, 'HC244's and HC273's for memory mapped I/O expansion but a lot of chips are involved.

Michael Karas