A processor made by Western Digital , consisting of at least four separate integrated circuit s, including the control circuitry unit, the ALU , two or four ROM chips with microcode , and timing circuitry.
The ALU chip contained twenty-six 8-bit register s and an 8-bit ALU , while the control unit supervised the moving of data, memory access, and other control functions. The ROM allowed the chip to function as either an 8- or 16-bit chip, with clever use of the 8-bit ALU . Further, microcode allowed the addition of floating-point routines (40 + 8 bit format), simplifying programming (and possibly producing a floating-point coprocessor).
Two standard microcode ROM s were available. This flexibility was one reason it was also used to implement the DEC LSI-11 processor as well as the WD Pascal Microengine .
(1994-11-18)