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Table of contents
1.
Introduction
2.
What is an 8085 microprocessor?
2.1.
Features of 8085 Microprocessor
3.
What is an 8086 Microprocessor?
3.1.
Features of 8086 Microprocessor
4.
Difference between 8085 and 8086 Microprocessor 
5.
Frequently Asked Questions
5.1.
What is the difference between 8085 and 8086 addressing modes?
5.2.
Can the 8085 and 8086 microprocessors be interfaced?
5.3.
What are the minimum mode and maximum mode of the 8086 microprocessor?
5.4.
What is the difference between 8085 and 8085A?
5.5.
What is the main difference between 8085 and 8051?
6.
Conclusion
Last Updated: Mar 27, 2024
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Difference between 8085 and 8086 Microprocessor

Author Nitika
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23 Jul, 2024 @ 01:30 PM

Introduction

The 8085 Microprocessor, created by Intel in 1976, preceded the 8086 Microprocessor. It utilized NMOS technology. The 8086 Microprocessor, also by Intel in 1976, is an enhanced version of the 8085.

Well, you're at the right place. In this article, we will discuss the difference between 8085 and 8086 microprocessors in detail and answer your questions.

Difference between 8085 and 8086 Microprocessor

What is an 8085 microprocessor?

"eighty-eighty-five" microprocessor is an 8-bit microprocessor designed with the help of N-channel Metal-Oxide Semiconductor (NMOS) technology by Intel in 1976. It was a simple and low-cost device which has been widely used in embedded systems, electronic gadgets, microwave ovens, and washing machines. It is binary compatible with the more-famous Intel 8080 but requires less

supporting hardware, allowing uncomplicated and inexpensive microcomputers to be built. An 8-bit microprocessor means it can provide 8-bit data simultaneously. The 8085 microprocessor has 40 pins and includes address bus-16 bit, program counter-16-bit, stack pointer-16 bit, registers 8-bit, +5V voltage supply, and operates at 3.2 MHz single segment CLK. In the following images, you will see the pin diagram configuration of the 8085 microprocessor and the architecture of the 8085 microprocessor.

8085 microprocessor
8085 microprocessor diagram

Features of 8085 Microprocessor

The following are the most salient features of the 8085 microprocessor−

  • It has an on-chip clock generator which requires a tuned circuit like LC, RC or crystal. It divides the oscillator frequency by two and generates a clock signal, which can be used for synchronizing external devices.
     
  • It has five hardware interrupts: 
    • TRAP
    • RST 7.5
    • RST 6.5
    • RST 5.5
    • INTR
       
  • 8085 has serial I/O control, which allows serial communication.
     
  • 8085 has control signals (IO/M, RD, WR) to control the bus cycles; hence, an external bus controller is unnecessary.
     
  • The external hardware can detect the machine cycle used by the microprocessor while executing status signals (IO/M, S0, S1). This feature of the 8085 microprocessor is handy when more than one processor is operating from common system resources.
     
  • 8085 features can be used to implement three-chip microcomputers with supporting I/O devices like IC 8155 and IC 8355.
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What is an 8086 Microprocessor?

The enhanced version of the 8085 microprocessor is the 8086 microprocessor. It was designed in 1978 by Intel using High-Performance Metal-Oxide Semiconductor (HMOS) technology. 8086 is a 16-bit microprocessor, it can process 16-bit of data in a single cycle with a 20-bit address bus.  and works in two modes, Maximum mode and Minimum mode. The 8086 Microprocessor has its uses in Personal computers, military equipment, high-performance computing, and industrial systems. In the following images, you will see the pin diagram configuration of the 8086 microprocessor and the architecture of the 8086 microprocessor.

8086 microprocessor
8086 microprocessor diagram

Features of 8086 Microprocessor

The following are the most salient features of the 8086 microprocessor−

  • The instruction queue of 8086 is capable of storing six instruction bytes from memory, resulting in faster processing.
     
  • 8086 was the first 16-bit processor to have a 16-bit ALU, registers, and internal and external data bus resulting in quicker processing.
     
  • It has three versions operating in different clock frequencies −
    • 8086 → 5MHz
    • 8086-2 → 8MHz
    • 8086-1 → 10 MHz
       
  • It uses two stages of pipelining to improve performance, i.e. Fetch Stage and Execute Stage 
     
  • Fetch Stage can prefetch up to 6 bytes of instructions and stores them in the queue.
     
  • Execute Stage executes the prefetched instructions.
     
  • 8086 has 256 vectored interrupts.
     
  • 8086 consists of 29,000 transistors.

Difference between 8085 and 8086 Microprocessor 

The following table showcases the difference between 8085 and 8086 microprocessors judging on different parameters.
 

Comparison Point

8085 Microprocessor

8086 Microprocessor

 

Definition

8085 Microprocessor is an 8-bit microprocessor designed by Intel and introduced in 1976.

8086 Microprocessor is a 16-bit microprocessor designed by Intel in 1978.

Data Bus

8-bit data bus.

16-bit data bus.

Type 

8085 is accumulator-based as the accumulator contains major activity in ALU Operations in store and updating calculations.

8086 is register-based as there is no specific Accumulator attached to the input of ALU.

Address Bus 

The address bus is 16 bits.

The address bus is 20 bits.

Processor

8085 is a single processor configuration microprocessor.

8086 is a multiprocessor configuration microprocessor.

Memory Capacity

The memory capacity is 64 KB, or 216 bytes

The memory capacity is 1 MB or 220 bytes

Clock Frequency

The operating frequency of 8085  is 3 MHz.

The operating frequency of 8086  has three versions of clock frequency, i.e.5MHz, 8MHz, and 10MHz 

Operation Mode

8085 has a Single Mode Of Operation.

Meanwhile. 8086 has Two Modes Of Operation.

  • Minimum Mode
  • Maximum Mode 

Operation Instructions.

8085 does not include multiplication and division instructions but does perform instructions like addition, decrement, subtraction, increment, comparison, AND, shift, OR, and X-OR.

8086 includes multiplication and division instructions song with performing all other instructions.

 

Pipelining

Pipelining is the process of fetching the next instruction while the present instruction is being executed.

8085 does not support pipelining.

8086 microprocessor supports pipelining as it has two independent units Execution Unit (EU) and Bus Interface Unit (BIU).

Instruction Queue

There exists no instruction queue in 8085.

It has an instruction queue of 16-bit that follows the FIFO principle.

Transistors

8085 contains 6500 transistors.

8086 contains 29000 transistors.

Memory Segmentation

8085 does not support memory segmentation.

8086 supports memory segmentation.

Flags

8085 has 5 flags which are: 

  • Carry flag (Cy),
  • Auxiliary carry flag (AC),
  • Sign flag (S),
  • Parity flag (P),.
  • Zero flag (Z).

 

8086 has 9 flags which are:

  • Sign Flag (S)
  • Zero Flag (Z)
  • Auxiliary Carry Flag (AC)
  • Parity Flag (P)
  • Carry Flag (CY) 
  • Overflow Flag (O) 

 

Duty Cycle

For one instruction cycle clock pulse is held high for 50% of the pulse.

For one instruction cycle clock, the pulse is held high for 33% of the pulse.

Cost

8085 is cheaper in comparison to the 8086 microprocessor.

8086 is effectively expensive.

You can also read 8051 Microcontroller Pin Diagram 

Frequently Asked Questions

What is the difference between 8085 and 8086 addressing modes?

The difference between 8085 and 8086 addressing modes is that 8085 primarily uses simple and limited addressing modes like immediate, direct, and register addressing, whereas 8086 offers a more versatile set of addressing modes, including effective address computation and complex modes like indexed and base-relative addressing.

Can the 8085 and 8086 microprocessors be interfaced?

Yes, the 8085 and 8086 microprocessors can definitely be interfaced. This process includes connecting the involved microprocessors' data, addresses, and control lines to match the memory requirements and microprocessor signals. Therefore, the interfacing circuit should be designed to fit the memory signal requirements with the signals of the microprocessor.

What are the minimum mode and maximum mode of the 8086 microprocessor?

The MN/MX indicates minimum mode or maximum mode. When MN/MX is 1, it indicates the minimum mode and when it is 0, it indicates the maximum mode. Minimum mode means that there can be only one processor i.e. 8086, while in the maximum mode, there can be multiple processors with 8086, like 8087 and 8089.

What is the difference between 8085 and 8085A?

The main difference between 8085 and 8085A is minor improvements and bug fixes in the 8085A version, enhancing its performance and reliability.

What is the main difference between 8085 and 8051?

The main difference between 8085 and 8051 microprocessors lies in their architecture and instruction sets. 8085 is an 8-bit microprocessor, while 8051 is a more complex microcontroller with integrated peripherals and a different instruction set.

Conclusion

In this article, we dived into the world of microprocessors and learnt about the 8085 & 8086 microprocessors and the difference between 8085 and 8086 microprocessors.

After reading about the 8085 microprocessor pin diagram, are you not excited to know more about Microprocessors like Microprocessor: 8257 DMA controller and many more topics? 

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