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Differences between 8085 and 8086 microprocessor
A microprocessor is an integrated circuit which can function as a central processing unit (CPU) of a computer system or a microcontroller. It is constructed by integrating millions of transistors, diodes, and resistors on a single electronic chip.
8085 and 8086 are two major types of microprocessors produced by Intel. Go through this article to find out the major differences between 8085 and 8086 microprocessors.
What is 8085 Microprocessor?
The 8085 microprocessor is an 8-bit microprocessor produced by Intel in 1976. The 8085 microprocessor has 8-bit long data bus, thus it can process 8-bit of data in a single cycle. The 8085 microprocessor offers an address bus of 16-bit. Hence, the maximum accessible memory capacity of 8085 microprocessor is 216 Bytes or 64 kB.
The 8085 microprocessor consists of an on-chip oscillator of 3 MHz. Basically, it is called 8-bit microprocessor because its ALU (arithmetic logic unit) size is of 8-bit. The ALU of 8085 microprocessor is capable of performing the operations such as addition, subtraction, increment, decrement, compare, AND, OR, X-OR, shift and complement.
In case of an 8085 microprocessor, the data being used for operation, intermediate results and the results produced by the ALU are stored in an accumulator. Therefore, the 8085 microprocessor is an accumulator based microprocessor. It performs the execution of programs in three stages viz. fetching, decoding and executing.
What is 8086 Microprocessor?
The 8086 microprocessor is a 16-bit microprocessor produced by Intel in 1976. The 8086 microprocessor is the improved version of the 8085 microprocessor. The 8086 microprocessor has a 16-bit data bus, which means it can process 16-bit of data in a single cycle. The address bus of the 8086 microprocessor is of 20-bit. Therefore, the maximum accessible memory capacity of 8086 microprocessor is 220 Bytes or 1 MB.
The 8086 microprocessor is available in different versions with a clock speed of 5 MHz, 8 MHz and 10 MHz. It is called 16-bit microprocessor because the ALU size of 8086 microprocessor is of 16-bit. It can perform the multiplication and division operations in addition to all the operations of the 8085 microprocessor.
The 8086 is a general purpose register based microprocessor which uses registers to store the data being used during operation and the results of the ALU. It has 14 internal registers each of 16-bit size.
Difference between 8085 and 8086 Microprocessors
The following table highlights the major differences between the 8085 microprocessor and the 8086 microprocessor.
| Parameter | 8085 Microprocessor | 8086 Microprocessor |
|---|---|---|
| Definition | The 8085 is an accumulator based 8-bit microprocessor which can process 8-bit of data at a time. | The 8086 is a register based 16-bit microprocessor which can process 16-bit of data at a time. |
| Microprocessor type | The 8085 microprocessor is an 8-bit accumulator based microprocessor. | The 8086 microprocessor is a 16-bit general purpose register based microprocessor. |
| Data bus size | The 8085 microprocessor has a data bus of 8-bit size. | The size of data bus of 8086 microprocessor is 16- bit. |
| Address bus size | The size of address bus of 8085 microprocessor is 16-bit. | The size of address bus of 8086 microprocessor is 20- bit. |
| Maximum accessible Memory capacity | The maximum accessible memory capacity of 8085 microprocessor is 216 bytes or 64 kB. | The 8086 microprocessor has maximum accessible memory capacity of 220/sup> bytes or 1 MB. |
| ALU (Arithmetic Logic Unit) size | The 8085 microprocessor has an 8-bit ALU. | The 8086 microprocessor has 16-bit ALU. |
| Clock frequency | The 8085 microprocessor has an on-chip oscillator of 3 MHz. | The 8086 microprocessor is available in three version with a clock speed (frequency) of 5 MHz, 8 MHz and 10 MHz. |
| Number of transistors | The 8085 microprocessor consists of 6500 transistors in its structure. | The 8086 microprocessor consists of 29000 transistors. |
| Operations | The 8085 microprocessor can perform addition, subtraction, increase, decrease, compare, AND, OR, X-OR, shift and complement. But, it does not support multiplication and division. | The 8086 microprocessor is able to perform all the operations of 8085 microprocessor and also multiplication and division. |
| Number of flags | The 8085 microprocessor has 5 flags, named carry, auxiliary carry, parity, zero and sign flag. | The 8086 microprocessor has 9 flags, named carry, auxiliary carry, parity, zero, sign, trap, interrupt, direction, and overflow flag. |
| Memory segmentation | The 8085 microprocessor does not support memory segmentation. | The 8086 microprocessor supports memory segmentation, i.e. the memory of 8086 microprocessor is segmented which means the 20-bit address bus can access 1 MB of memory but it uses only four 64 kB segments from it. |
| Modes of operation | The 8085 microprocessor supports only a single mode of operation. | The 8086 microprocessor supports two modes of operation viz. minimum mode and maximum mode. |
| Pipelining architecture | The pipelining architecture is not supported by the 8085 microprocessor. | The 8086 microprocessor supports pipelining architecture. |
| Processor configuration | 8085 is a single processor configuration microprocessor. | 8086 is a multiprocessor configuration microprocessor. |
| Instruction queue | 8085 microprocessor does not have an instruction queue. | 8086 microprocessor has an instruction queue of 6 bytes which is stored in FIFO (First In First Out) register. |
| Cost | 8085 microprocessor is cheaper. | 8086 microprocessor is relatively expensive than 8085 microprocessor. |
Conclusion
From the above discussion, we can conclude that the 8086 microprocessor provides more features than an 8085 microprocessor. However, 8086 microprocessors are more expensive as compared to the 8085 microprocessor.
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