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Differences between 8085 and 8086 microprocessor

Last Updated : 19 Sep, 2024
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A Microprocessor is an important part of a computer architecture without which you will not be able to perform anything on your computer. It is a programmable device that takes in input performs some arithmetic and logical operations over it and produces the desired output. As famous processors, there are 8085 and 8086 microprocessors made by Intel company. Both are on the same family with many similarities, however, their objectives are different and as well have different structure and functionality. Comparing the 8085 and 8086 microprocessor architecture is very valuable for whoever is working in hardware design or system development since it aids in choosing on which processor to use depending on the need.

What is 8085 Microprocessor ?

8085 Microprocessor is a predecessor of version 8086 Microprocessor, designed by Intel in 1976 with the help of NMOS technology. It includes a data bus of 8 bits, and 16 bits of the address bus, having a +5V voltage supply, and operates at 3.2 MHz single segment CLK.

It has an internal clock generator and functions on a clock cycle having a duty cycle of 50%. 246 total operational codes and 80 instructions are present in the 8085 Microprocessor.

Advantages of 8085 Microprocessor

  • Simple Architecture: The 8085 is easier in its design and implementation and can be easily understood in simple applications.
  • Low Power Consumption: It needs less power to run hence can be used in small embedded systems and small related projects.
  • Widely Used in Education: Maybe because of its programmability and ease of implementation it is widely taught in academic institutes.

Disadvantages of 8085 Microprocessor

  • Limited Processing Power: It has been designed to work as an 8-bits microprocessor and thus operates on fewer bits and limited data and provides a limited performance compared to the modern microprocessors.
  • Limited Memory Addressing: Another disadvantage of the 8085 is that it can address only 64 K of memory and as a result, cannot be applied to more complicated systems.
  • Slower Speed: The clock speed of 8085 is 3 MHz which is significantly slower as compared to present day processor.

What is 8086 Microprocessor?

8086 Microprocessor is an advanced version of the 8085 Microprocessor, designed by Intel in 1976. The number 8086 denotes the IC number of this microprocessor. It is a 16-bit microprocessor. It has 16 bits of the data bus, which is why it can read or write either 16 bits or 8 bits of data at a time. It has 20 bits of address lines that can access 220 address locations.

It works in 2 modes-

  • Maximum mode
  • Minimum mode

Advantages of 8086 Microprocessor

  • Higher Performance: Thanks to the 16-bit structure, in its turn, the 8086 is designed for dealing with larger needed sizes of data and more complex arithmetic operations.
  • Larger Memory Addressing: The 8086 can address up to 1 Mega Byte of memory space, and this is good for other complex systems.
  • Faster Speed: The 8086 operates at up to 10 MHz and provides performance which is much better than 8085.
  • Supports Multitasking: 8086 is good for the complex computing structure adoring from the fact that it can handle several chores better than the simple architecture microprocessors.

Disadvantages of 8086 Microprocessor

  • More Complex Architecture: 8086 is much more complicated than 8085 in terms of the architecture that makes it harder to learn and use than 8085 in case of programming needs.
  • Higher Power Consumption: Another disadvantage concerns the power consumption: the 8086 processor is rather ‘hungry’ due to its higher speed and greater processing capabilities in contrast to the 8080.
  • Costlier to Implement: The 8086 is a more demanding and difficult chip to interface with far more resources needed to implement it and so, the implementation of the 8086 requires more resources and more money.

Differences between 8085 and 8086 Microprocessor

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

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

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

In the 8086 microprocessor, we can give the 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]

The 8085 microprocessor operates at 5 volts.The 8086 microprocessor operates at 5 or 3.3 volts.
Less powerful and faster than 8086 microprocessorThe 8086 microprocessor is faster and more powerful than the 8085 microprocessor.
The 8085 microprocessor handles interrupts using a software-based approach.The 8086 microprocessor uses a hardware-based approach.

Conclusion

Both 8085 and 8086 are different in terms of architectural, performance and usability. The provided 8085 is less complex, requires less power, and is more suitable for educational systems as well as small and medium scaled embedded systems. In contrast, the 8086 contain more capacity, bigger memory size and faster processing, thus more appropriate for complicated systems and multi-tasking. Whether to use native or hybrid approaches depends on whether one wants to build a relatively simple application or an application that offers high performance.


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