Microprocessors | SparkEasy
👉A control unit of a microcomputer – built on a single Integrated circuit, capable of performing arithmetic and logical operation and helps computers to communicate with other devices connected to it, is known as Microprocessor.
It contains ALU, Control Unit, and a Register Array. Here, Arithmetic Logic Unit – performs arithmetic and logical operations on the data, which is received from an input device or memory of a computer system. Similarly, Control Unit – controls the flow of data and instructions, and Register Array – contains registers identified by letters like B, C, D, E, H, L, and accumulator.
The first commercially launched microprocessor/first-generation microprocessor – the Intel 4004, was a 4-bit microprocessor. A 4-bit broad memory location is usually called a – nibble.
The Intel 4004 microprocessor’s instruction set contained only 45 instructions. It weighed much less than an ounce. Intel 4004 was slow compared to the 30-ton ENIAC computer in 1946 (100,000 instructions executed per second).
The architecture of 8088 Microprocessors | SparkEasy
Below is the functional block diagram of Intel 8088 Microprocessors. It includes two main sections: the Execution Unit, which takes care of the processing, including arithmetic and logic. Furthermore, the second one is the Bus Interface Unit which controls the passing of information between the processor and the devices outside of the processor, such as memory, I/O ports, storage devices, etc.
➥General Registers
These registers are categorized into two sets: data and address. The data registers are for calculations; the address registers contain memory addresses and are used to point to the locations in memory where data will be retrieved or stored.
The diagram shows four pairs of registers – AH, AL, BH, BL, CH, CL, DH, and DL. These are the data registers. Each of these registers is 8 bits long.
Each pair, however, can also operate as a single 16-bit register. AH and AL can operate as a pair referred to as AX (Accumulator Register). Similarly, BH and BL form a pair BX (Base Register), CH and CL form a pair CX (Counter Register), and DH and DL form a pair referred to as DX (Data Register).
Below the data registers in the block diagram are the address registers: SP, BP, DI, and SI. These are officially referred to as the pointer (SP and BP) and index registers (DI and SI). These registers are used with the segment registers to point to specific addresses in the processor’s memory space.
SP is the stack pointer that points to the “top plate” or last piece of data placed on the stack. BP (base pointer), SI (source index), and DI (destination index) are all pointers that the programmer has for their use.
➥The Flags
The Flag registers – show the status of the task. It is a Special Purpose Register, an 8-bit register, but only 5-bit is used for any operation. The flag becomes set or reset after arithmetic and logical operation.
➥Arithmetic Logic Unit
It is the computation portion of the Execution Unit. Any time arithmetic or logic needs to be performed on numbers, the numbers are sent from the general registers to the Arithmetic Logic Unit, the ALU performs the function, and the result is sent back to the general registers.
➥Execution Unit Control System
The execution unit control system is a set of gates that control the timing, passing of data, and other items within the execution unit. It does not necessarily know the details of the operation, but its plans what happens, where it happens, and when.
➥Instruction Pointer
The Instruction Pointer can be found toward the bottom of the group of registers in the center of the Bus Interface Unit. It is an address register like the Execution unit’s SP, BP, DI, and SI registers. However, its purpose is different. The IP points to the next instruction to execute from memory.
➥Segment Registers
In the center of the Bus Interface Unit section of the processor organizational block diagram is a set of registers labeled CS, DS, SS, and ES. These four registers are the segment registers used in conjunction with the pointer and index register to store and retrieve items from the memory space.
➥Pipelining
It is a process of arrangement of hardware elements of the microprocessors so that their overall performance is increased. Simultaneous execution of more than one instruction takes place in a pipelined processor.
➥Instruction Queue
The Instruction Queue is the mechanism in the Intel 8088 processor that handles the pipelining function.