ISA Storage Architecture

Abstract

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• Defines the way how a computer system manages and accesses data storage

Important

Accumulator ISA and Stack ISA use implicit operands.

The implicit operand in Stack-based architecture is “top-of-the-stack” whereas in accumulator-based architecture it is a special register called an accumulator.

Accumulator ISA

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1. load A: Load value from Main Memory into accumulator which is a special Register!
2. add B: Add value from Main Memory and value in the accumulator. The sum is stored back to the accumulator
3. store C: Store value in accumulator into Main Memory

Load-Store ISA

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• Also known as Register-Register ISA
• The data is decoupled from the Register to Main Memory

Important

The only Instruction that can access main memory are load and store!

Data Loading

Can only load data at Word boundaries.

Memory-Memory ISA

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Stack ISA

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1. push A, push B: We load values from Main Memory onto the Stack
2. add: Remove the top 2 values in the Stack, add them, and load the sum onto top of Stack
3. pop C: Transfer value at top of Stack to Main Memory