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Differences between 8085 and 8086 microprocessor

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  • Difficulty Level : Easy
  • Last Updated : 30 May, 2022

In the changing world of technologies, the devices used are also changing. Let us take a look at the changes between 8085 series of microprocessors and 8086 series of microprocessors.

Serial No.8085 microprocessor8086 microprocessor
1The data bus is of 8 bits.The data bus is of 16 bits.
2The address bus is of 16 bits.The address bus is of 20 bits.
3The memory capacity is 64 KB. Also 8085 Can Perform Operation Up to 28 i.e. 256 numbers. A number greater than this is to taken multiple times in 8 bit data bus.The memory capacity is 1 MB. Also 8086 Can Perform Operation up to 216 i.e. 65,536 numbers.
4The input/output port addresses are of 8 bits.The input/output port addresses are of 8 bits.
5The operating frequency is 3.2 MHz.The operating frequency is 5 MHz, 8MHZ,10MHZ.
68085 MP has Single Mode Of Operation.8086 MP has Two Modes Of Operation. 1. Minimum Mode = Single CPU PROCESSOR 2. Maximum Mode = Multiple CPU PROCESSOR.
7It not have multiplication and division instructions.It have multiplication and division instructions.
8It does not support pipe-lining.It supports pipe-lining as it has two independent units Execution Unit (EU) and Bus Interface Unit (BIU).
9It does not support instruction queue.It supports instruction queue.
10Memory space is not segmented.Memory space is segmented.
11It consists of 5 flags(Sign Flag, Zero Flag, Auxiliary Carry Flag, Parity Flag, Carry Flag).It consists of 9 flags(Overflow Flag, Direction Flag, Interrupt Flag, Trap Flag, Sign Flag, Zero Flag, Auxiliary Carry Flag, Parity Flag, Carry Flag).
12It is low cost MicroprocessorIt is comparatively High cost Microprocessor.
13There are 5 Addressing Modes.There are 11 addressing modes.
14There is no concurrency in Fetching, Decoding and execution.There is Concurrency in Fetching , Decoding and Execution because of instruction queue.
15It has almost 6500 transistors.It has almost 29000 transistors.
16It is Accumulator based Microprocessor because Accumulator contains major activity in ALU Operations in store and updating calculations.It is General Purpose Registers(GPR) based microprocessor because there is not specific Accumulator attached with the input of ALU. all GPR’s are connected with it via Bus.
17Integer ,Decimal and Hexadecimal arithmetic is supportedIt also supports ASCII Arithmetic over Integer, Decimal and Hexadecimal.
18It needed less external hardware.It needed more external hardware. Because here more than 1 processor works and additional external processor can also be employed as per requirements.
19It runs over 50% duty cycle. That means for one instruction cycle clock pulse held high for 50% of the pulse.It runs over 33% duty cycle. That means for one instruction cycle clock pulse held high for 33% of the pulse.
20In 8085 Microprocessor for immediate addressing modes there is instructions containing “I” in it. e.g. MVI , LXI etc.In 8086 Microprocessor for immediate addressing modes there is no instruction containing “I” in it. In other words there is no MVI instruction in 8086 for moving/transfer data. Only MOV instruction is sufficient.
21

In 8085 microprocessor ADD ,SUB instructions were carried out in Accumulator by default. It is used only 1 register for arithmetic operation because another register is fixed and it is accumulator.

Example : ADD C  will do [A]<- [A] + [C]

In 8086 microprocessor , we can give source and destination register and according to that addition or any arithmetic operations will be performed.

For Example : ADD AX,BX  will do [AX] <- [AX] + [BX]

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