Question

what is the minimum number of instruction can a load/store ISA have?

Answer 1

The Instruction Set Architecture (ISA) is the part of the processor that is visible to the programmer or compiler writer. The ISA serves as the boundary between software and hardware. We will briefly describe the instruction sets found in many of the microprocessors used today. The ISA of a processor can be described using 5 catagories:

Operand Storage in the CPU

Where are the operands kept other than in memory.

Number of explicit named operands

How many operands are named in a typical instruction.

Operand location

Can any ALU instruction operand be located in memory Or must all operands be kept internaly in the CPU.

Operations

What operations are provided in the ISA.

Type and size of operands

What is the type and size of each operand Of all the above the most distinguishing factor is the first.

The 3 most common types of ISAs are:

1. Stack - The operands are implicitly on top of the stack.
2. Accumulator - One operand is implicitly the accumulator.
3. General Purpose Register (GPR) - All operands are explicitely mentioned, they are either registers or memory locations.