The MCP-1600 is a multi-chip 16-bit microprocessor introduced by Western Digital in 1975 and produced through the early 1980s.

The PTA serves to generate new microinstruction fetch addresses as a function of several parameters.

Microcode could be developed using a DEC LSI-11 computer with the KUV11-AA Writable Control Store (WCS) option.

This option allowed programming of the internal 8-bit micromachine to create application-specific extensions to the instruction set.

The WCS is a quad Q-Bus board with a ribbon cable connecting to an open MCP-1600 microcode ROM socket.

"It works well enough to execute the first few dozen p-code instructions of the ACD PDQ-3 boot ROM before going into the weeds."