MCP-1600
The MCP-1600 is a multi-chip microprocessor made by Western Digital in the late 1970s through the early 1980s. Used in the Pascal MicroEngine, the WD16 processor in the Alpha Microsystems AM-100, and the DEC LSI-11 microcomputer, a cost-reduced and compact implementation of the DEC PDP-11.

There are three types of chips in the chip-set:
 CP1611 RALU - Register ALU chip
 CP1621 CON - Control chip
 CP1631 MICROM - Mask-programmed microcode ROM chip (512 – 22 bit words)

The chips use a 3.3MHz four phase clock and four power supply voltages (+5V, +12V, -12V, and -5V), as required by the P-channel enhancement gate process then available at Western Digital.  Internally the MCP-1600 was a (relatively fast) 8-bit processor that can be micro-programmed to emulate a 16-bit CPU.  Up to four MICROMs are supported, but usually two or three could hold the needed microprogram for a processor.  

John Wallace was the Project Manager and designed the 1621, Mike Briner designed the 1611, and later became a Senior VP at Silicon Storage Technology.  Bill Pohlman was the design engineering manager and he later was Project Manager for the Intel 8086 processor.

A clone of the CP1611 and CP1621 was manufactured in the Soviet Union under the designation KR581IK1 and KR581IK2 (). The Soviet 581 series included other members of the MCP-1600 family as well.

References

16-bit microprocessors