Types of Architecture based on Input to ALU

Basic Design of Computer says ALU takes two types of inputs (Input Operand, Function Code) to execute a program and generate two types of outputs (Result, Various status signal.) 

Let’s Go into deeper and see types of Architecture based on how ALU gets input means from where ALU gets input operands. we assume ALU required two input operands to perform the operation.

Types Of Architecture :
1. Accumulator-Based Architecture :In this type of architecture, ALU gets one of its input operands from Accumulator( AC ) and another input operand from anywhere may be from the register, memory, etc. After getting input operand ALU performs an operation on operands and Result will be stored in Accumulator(AC).

2. Register-Based Architecture :
In this type of architecture, ALU takes both two inputs operands from Register, After getting the input operand ALU performs an operation on operands and the result will be stored in Accumulator(AC).

suppose initially your input operands stored into memory then first you have transferred from the memory to one of the registers for execution.

3. Register-Memory Architecture :
In this type of architecture, ALU gets one of its input operands from Register and another input operand not bounded to taken from register only it can be taken from memory (i.e. Not Compulsory input taken from Memory only its optional either from register or memory). After getting input operand ALU performs an operation on operands and  Result will be stored in Accumulator(AC).

4. Complex-System Architecture :
In this type of architecture, No Restriction from where input operands go to ALU. Both the input operands are free to take from anywhere either from memory or register etc. After getting the input operand ALU performs an operation on operands and the Result will be stored in Accumulator(AC).

5. Stack-Based Architecture :
In this type of architecture, ALU gets both of its input operands taken from Stack by just pop two topmost elements of the stack after getting input operand ALU performs an operation on operands and  Result will be stored in Accumulator(AC).

We also divide Architecture based upon the maximum size of input operands. e.g.,

32-bit Architecture, 64-bit Architecture based upon the processor word length