Tutorial 6 - Part 2

COMPUTER ORGANIZATION AND ARCHITECTURE SESSION: 2009/2010 Tutorial 6 – Part 2 1. Write the sequence of micro-operations required for the bus structure of Fig. Q1 to add a number to the AC when the number is: i. ii. iii.

an immediate operand a direct-address operand an indirect-address operand

Fig. Q1-A CPU with Internal Bus 2. In a microprogrammed control unit 8 control words are provided for each machine instruction routine. Machine instruction opcodes have 5 bits, and control memory has 1024 words. Suggest a mapping from the instruction register to the control address register. 3. What are the advantages and disadvantages of microprogrammed control unit compared to hardwired control unit? Explain why hardwired control unit is usually used for RISC and microprogrammed control unit for CISC architectures. 4. A processor has 16 registers, an ALU with 16 logic and 16 arithmetic functions, and a shifter with 8 operations, all connected by an internal processor bus. Design a microinstruction format to specify the various micro-operations for the processor.