Intel 8086

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Features of 8086 Microprocessor

1) 8086 has 16-bit ALU; this means 16-bit numbers are directly processed by 8086.
2) It has 16-bit data bus, so it can read data or write data to memory or I/O ports either 16 bits or 8 bits at a time.
3) It has 20 address lines, so it can address up to 220 i.e. 1048576 = 1Mbytes of memory (words i.e. 16 bit numbers are stored in consecutive memorylocations). Due to the 1Mbytes memory size multiprogramming is made feasible as well as several multiprogramming features have been incorporated in 8086 design.



Architecture of 8086 (contd..)

Fetching the next instruction while current instruction is under execution is called pipelining.
What happens to queue when jump or call
instruction is executed ?
When 8086 is reset the contents of IP are 0000 H and contents of CS are FFFF H. Other registers are cleared to 0000 h.



Advantages of memory segmentation


Allow the memory capacity to be 1Mb even though the addresses associated with the individual instructions are only 16 bits wide.
Facilitate the use of separate memory areas for the program, its data and the stack.
Permit a program and/or its data to be put into different areas of memory each time the program is executed.
Multitasking becomes easy.