This PCB contains the main system memory as well as the video control circuit. The main memory is composed of AM9016 DRAM chips, totaling 96k of memory. The video circuit contains it's own, separate 16k of DRAM built from D2114 chips. The video circuit also contains a the character generator ROM as well as a TMS9927 CRT controller chip for interfacing with the monitor.

The Memory is split up into four primary sections. From 8000 - BFFF is the paged memory area, this is where the expanded memory lies, and how they are achieving 96k of memory with only a 16-bit address bus.

Below are the I/O Addresses and what their function is.

These are the official Wang schematics, provided by the awesome Rich.

All schematics are available here in PDF format.

MCM2708 - Character Generator ROM