Q. What do you mean by Execution Unit?
Execution unit performs all ALU operations. Execution unit of 8086 is of 16 bits. It also contains the control unit that instructs bus interface unit about which memory location to access and what to do with data. CU also executes execution and decoding of instructions. EU comprises the subsequent:
(a) Control Circuitry, Instruction Decoder and ALU
The 8086 control unit is mainly micro-programmed control. Additionally it has an instruction decoder that translates an instruction in sequence of micro operations. ALU executes the needed operations under the control of CU that issues essentialcontrol and timing sequences.
(b) Registers
All CPUs have a defined number of operational registers. 8086 has various general purpose and special purpose registers. We would discuss these registers in subsequent sections.