A simple single board computer based on the Mostek MK38P70 or MK38P73 MCU. The MK38P70 is the "piggyback" version of the Mostek's MK3870 which is a second generation refinement of the Fairchild F8 MCU. The MK38P73 is a variation of the Mostek MK38P70 which contains a hardware serial port. The MK38P70 and MK38P73 feature 32 bits of I/O, 64 bytes of 'scratchpad' RAM, 64 bytes of 'executable' RAM and a binary timer.
Assemble the source with the Macro Assembler AS.
Here's another F8 based single board computer that's a bit more complex
MK38P73 SBC
MK38P70 SBC Schematic
MK38P73 SBC Schematic