Bus connection ribbon cable leads to TWO strange processors. One TS68008 which is a weird 32bit CPU with only an 8 bit interface. The second is an Intel 8051 CPU.  The random 32 bit processor is strange.

I have to wonder if this is not actually the "brain" of the machine and the two z80's on the main board are just for IO and presenting data to the video hardware maybe?

Bunch of SRAM and some card ID selector switches. Also some random LSB/MSB LED's.