ALU 101 ALU Hardware Components 2

Question 1

What is the role of carry lookahead logic in an ALU?

Accepted Answer

To compute carry bits in parallel rather than sequentially

Answer

Carry lookahead logic calculates carry signals simultaneously using generate and propagate terms, eliminating ripple delay.

Question 2

Which hardware component stores intermediate values between ALU operations in a typical CPU datapath?

Accepted Answer

General-purpose registers

Answer

General-purpose registers hold operands and intermediate results so the ALU can quickly access them without accessing main memory.

Question 3

What is a barrel shifter used for in an ALU?

Accepted Answer

Performing multi-bit shifts in a single clock cycle

Answer

A barrel shifter uses a network of multiplexers to shift data by an arbitrary number of bit positions in one cycle.

Question 4

In ALU design, what does the term 'bit-sliced' architecture mean?

Accepted Answer

The ALU is built from identical 1-bit sections that can be cascaded

Answer

A bit-sliced ALU consists of identical 1-bit processing units connected in series to handle any desired word width.

Question 5

What is the purpose of an inverter (NOT gate) in an ALU subtraction circuit?

Accepted Answer

To compute the two's complement negation as part of subtraction

Answer

Inverting the subtrahend bits and adding 1 (via carry-in) implements two's complement subtraction using the existing adder hardware.

ALU 101 - Arithmetic Logic Unit 101 Exam Practice Test