Drawbacks of this Single Cycle Processor
Long cycle time:
- Cycle time must be long enough for the load instruction:
- PC’s Clock -to-Q +
- Instruction Memory Access Time +
- Register File Access Time +
- ALU Delay (address calculation) +
- Data Memory Access Time +
- Register File Setup Time +
- Clock Skew
Cycle time is much longer than needed for all other instructions. Examples:
- R-type instructions do not require data memory access
- Jump does not require ALU operation nor data memory access