Memory Segmentation: 8085 microprocessor which has 16-address lines and also the memory registers, and SP is also 16-bit, the complete memory is organized as one contiguous block of memory. But, 8086 has 20-address lines whereas the size of all its registers is 16-bits, there is no way to hold this address in any memory address registers. For small, conventional and uni-programming(single program) applications utilizing less than 64KB memory size this may not be problem. But 8086 is design for developing utility programs like .com utilizing less than 64KB memory and .exe programs requiring more than 64KB of memory this pauses a problem. For better management and utilization of memory, designers of 8086 came up with a new concept of logically dividing the

Programming Model of 8086: As a programmer of the 8086 we must be familiar with the various registers in the execution unit (EU) and Bus Interface Unit (BIU). Registers of 8086 Data Group of Registers: These registers are also called the general purpose registers and are used to store both the operands and the result. These are all 16 bit registers and each of these registers can be used as a whole 16 bit register or as part (8 bit) register. The register AX is used as accumulator and the register BX, CX and DX in addition to being general purpose registers can also be used for special purpose roles as given below: AX Accumulator BX base register CX  Counter DX to hold i/o address during certain i/o operations. Pointer and Index

Introduction: 8086 is different from its predecessor 8080 and 8085 processors in the sense that the address generation, fetching the instructions from the memory are quite complex. Also 8086 contains an instruction queue of 6 bytes used for pre-fetching the instructions from the memory. Internally 8086 is divided into two logical units, these are are given in figure-1: Execution Unit: It is responsible for executing the instructions fetched from memory Bus Interface units: It is responsible for pre-fetching the instructions from the memory The following paragraphs give a detailed discussion on these units. Figure-2 below gives the detailed architecture of the 8086 microprocessor:   Execution Unit The EU consists of a the following parts: General purpose Registers: AX, BX, CX and DX Index Registers

Introduction Intel 8086 a 16-bit microprocessor was introduced in year 1978. It was source code compatible with its predecessor 8080 and 8085 microprocessors. It was the first microprocessor that was part of a big breakthrough in the era of computing and was used as a main processor in PCXT personnel computers. It was developed using very large scale transistors and used approximately 29000 transistors. It has a number of added functionality as compared to 8080 and 8085 microprocessor making it to perform advanced and very complex activities. It is rich in terms of addressing, number and type of instruction, functionality by supporting single processor mode or multiprocessor communication. Some Features of 8086 microprocessor: 16-bit processor 20-bit address bus thus addressing up to