Conclusion
We can build an ALU to support the MIPS instruction set
- key idea: use multiplexor to select the output we want
- we can efficiently perform subtraction using two’s complement
- we can replicate a 1-bit ALU to produce a 32-bit ALU
Important points about hardware
- all of the gates are always working
- the speed of a gate is affected by the number of inputs to the gate
- the speed of a circuit is affected by the number of gates in series (on the “critical path” or the “deepest level of logic”)
Our primary focus: comprehension, however,
- Clever changes to organization can improve performance (similar to using better algorithms in software)
- we’ll look at two examples for addition and multiplication