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In 1946, a model for computer architecture was introduced and became known as von Neumann Architecture. Since 1950, the von Neumann model provided uniformity in subsequent computer designs. The von Neumann Architecture was considered innovative as it introduced an idea of allowing machine instructions and data to share memory space. The von Neumann model is composed of 3 major parts, the arithmetic logic unit (ALU), the memory, and the instruction processing unit (IPU). In von Neumann machine design, the IPU passes addresses to memory, and memory, in turn, is routed either back to the IPU if an instruction is being fetched or to the ALU if data is being fetched.[21] Von Neumann’s machine design uses a RISC (Reduced instruction set computing) architecture, which means the instruction set uses a total of 21 instructions to perform all tasks. (This is in contrast to CISC, complex instruction set computing, instruction sets which have more instructions from which to choose.) Addresses, operations and data types comprise this instruction set. With von Neumann architecture, main memory along with the accumulator (the register that holds the result of logical operations)[22] are the two memories that are addressed. Operations can be carried out as simple arithmetic (these are performed by the ALU and include addition, subtraction, multiplication and division), conditional branches (these are more commonly seen now as “if” statements or “while” loops. The branches serve as ‘go to’ statements), and logical moves between the different components of the machine, i.e., a move from the accumulator to memory or vice versa. Von Neumann architecture accepts fractions and instructions as data types. Finally, as the von Neumann architecture is a simple one, its register management is also simple. The architecture uses a set of seven registers to manipulate and interpret fetched data and instructions. These registers include the "IR (instruction register), IBR (instruction buffer register), MQ (multiplier quotient register), MAR (memory address register), and MDR (memory data register)."[21] The architecture also uses a program counter (PC) to keep track of where in the program the machine is.[21] |
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