MP1

EXPERIMENT NO 1
AIM: To study history and evolution of Microprocessors
THEORY:
Microprocessor
 	A microprocessor is a computer processor that incorporates the functions of a computer's central processing unit (CPU) on a singleintegrated circuit (IC), or at most a few integrated circuits. The microprocessor is a multipurpose, programmable device that acceptsdigital data as input, processes it according to instructions stored in its memory, and provides results as output.
History and Evoluation of Microprocessors:
Microprocessor journey started with a 4-bit processor called 4004, it was made by Intel corporation in 1971. it was 1st single chip processor. then the idea was extended to 8-bit processors like 8008, 8080 and then 8085 (all are Intel products). 8085 was a very successful one among the 8-bit processors, however its application is very limited bcoz of its slower computing
some years later Intel came up with its 1st 16-bit processors 8086. at the same time other manufacturers were also making processors like 68000 (by motorola), Zilog z-80, General instrument PIC16X, MOS Technology 6502, etc...in 1979 Intel released a modified version of 8086 as 8088. next intel started updating 80x86 series by introducing 80286, 80386, 80486, pentium and then pentium series. After 80486, the next processor in series was to be said 80586, but Intel named it as pentium bcoz of  its copyright problem. further updation in pentium resulted in pentium-I, pentium-II, etc.
Intel introduced its first 4-bit microprocessor 4004 in 1971 and its 8-bit microprocessor 8008 in 1972. During the 1960s, computer processors were constructed out of small and medium-scale ICs—each containing from tens of transistors to a few hundred. The Intel 4004 is generally regarded as the first commercially available microprocessorand cost $60. The first known advertisement for the 4004 is dated November 15, 1971 and appeared in Electronic News. The project that produced the 4004 originated in 1969, when Busicom, a Japanese calculator manufacturer, asked Intel to build a chipset for high-performance desktop calculators. Busicom's original design called for a programmable chip set consisting of seven different chips.
The Intel 8008 ("eight-thousand-eight" or "eighty-oh-eight") is an early byte-oriented microprocessor designed and manufactured by Intel and introduced in April 1972. It was an 8-bit CPU with an external 14-bit address bus that could address 16KB of memory. Originally known as the 1201, the chip was commissioned by Computer Terminal Corporation (CTC) to implement an instruction set of their design for their Datapoint 2200 programmable terminal.
The Intel 8080 ("eighty-eighty") was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It was an extended and enhanced variant of the earlier 8008 design, although without binary compatibility. The initial specified clock frequency limit was 2 MHz, and with common instructions having execution times of 4, 5, 7, 10, or 11 cycles. This meant that it operated at an effective speed of a few hundred thousand instructions per second.
The Intel 8085 ("eighty-eighty-five") is an 8-bit microprocessor produced by Intel and introduced in 1977. It is software-binary compatible with the more-famous Intel 8080 with only a few minor instructions added. However, it required less support circuitry, allowing simpler and less expensive microcomputer systems to be built.
The 8086[1] ("eighty eighty-six", also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The Intel 8088, released in 1979, was a slightly modified chip with an external 8-bit data bus(allowing the use of cheaper and fewer supporting ICs), and is notable as the processor used in the original IBM PC design, including the widespread version called IBM PC XT.The 8086 gave rise to the x86 architecture which eventually became Intel's most successful line of processors.

 8086 Microprocessor
1. Features of the Intel 8086
•	8086 is a 16bit processor.
•	 It’s ALU, internal registers works with 16bit binary word - 8086 has a 16bit data bus.
•	It can read or write data to a memory/port either 16bits or 8 bit at a time
•	8086 has a 20bit address bus which means, it can address upto 220 = 1MB memory location
•	Frequency range of 8086 is 6-10 MHz
•	16 bit data bus (→word)
•	24 addressing modes
•	It has fourteen 16-bit registers.
•	 Its operating voltage is 5 volts.
•	It has three version based on the frequency of operation:
a)8086 -> 5MHz
b)8086-2 ->8MHz
c)8086-1 ->10 MHz
•	Operates in two modes:-8086 operates in two modes:a)Minimum Mode: A system with only one microprocessor.b)Maximum Mode:-A system with multiprocessor.
•	8086 uses memory banks:-The 8086 uses a memory banking system. It means entire data is not stored sequentially in a single memory of 1 MB but memory is divided into two banks of 512KB.
•	Interrupts:-8086 has 256 vectored interrupts.
•	Multiplication And Division:-8086 has a powerful innstrction set. So that it supports Multiply and Divide operation.
2.8086 Architecture



                                    Fig 1. Architecture of 8086
The internal architecture of Intel 8086 is divided into two units, viz., Bus Interface Unit (BIU) and Execution Unit (EU).
(a)Bus Interface Unit (BIU )
The Bus Interface Unit (BIU) generates the 20-bit physical memory address and provides the interface with external memory (ROM/RAM). As mentioned earlier, 8086 has a single memory interface. To speed up the execution, 6-bytes of instruction are fetched in advance and kept in a 6-byte Instruction Queue while other instructions are being executed in the Execution Unit (EU). Hence after the execution of an instruction, the next instruction is directly fetched from the instruction queue without having to wait for the external memory to send the instruction. This is called pipe-lining and is helpful for speeding up the overall execution process.
8086's BIU produces the 20-bit physical memory address by combining a 16-bit segment address with a 16-bit offset address. There are four 16-bit segment registers, viz., the code segment (CS), the stack segment (SS), the extra segment (ES), and the data segment (DS). These segment registers hold the corresponding 16-bit segment addresses. A segment address is the upper 16-bits of the starting address of that segment. The lower 4-bits of the starting address of a segment is always zero. The offset address is held by another 16-bit register. The physical 20-bit address is calculated by shifting the segment address 4-bit left and then adding that to the offset address.
(b)ExecutionUnit(EU):
 The execution unit contains the Data and Address registers, the Arithmetic and Logic Unit and the Control Unit. The Bus Interface Unit contains Bus Interface Logic, Segment registers, Memory addressing logic and a Six byte instruction object code queue (4-byte instruction object-code queue in case of 8088 microprocessor). The execution unit and the Bus Interface unit operate asynchronously. The EU waits for the instruction object code to be fetched from the memory by the BIU. The BIU fetches or pre-fetches the object code (16-bits at a time) and loads it into the six bytes queue. Whenever the EU is ready to execute a new instruction, it fetches the instruction object code from the front of the instruction queue and executes the instruction in specified number of clock periods. If memory or Input/output devices must be accessed in the course of executing an instruction, then the EU informs the BIU of its needs. The BIU completes its operation code (opcode) fetch cycle, if in progress, and executes an appropriate external access machine cycle in response to the EU demand. The BIU is independent of the EU and attempts to keep the six-bytes queue filled with instruction object codes. If two or more of these six bytes are empty, then the BIU executes instruction fetch machine cycles as long as the EU does not have an active request for the bus access pending. If the EU issues a request for the bus access while the BIU is in the middle of an instruction fetch machine cycle, then the BIU will complete the instruction fetch machine cycle before honoring the EU bus access request. The EU does not use machine cycles; it executes instructions in some number of clock periods that are not subjected to any type of machine cycles. The only time clock periods are grouped is clock when the bus control logic wishes to access memory or I/O devices.

3. Addressing Modes:
1.        Register Addressing
2.	Immediate Addressing
3.	Direct Addressing
4.	Register Indirect Addressing
5.	Based Addressing
6.	Indexed Addressing
7.	Based Index Addressing
8	String Addressing
9        Direct I/O port Addressing
 10.     Indirect I/O port Addressing
 11.     Relative Addressing
12.    Implied Addressing
4.Pin Diagram Of 8086 Microprocessor

                        Fig 2. Pin Diagram Of 8086 Microprocessor
5. Advantages of 8086 Microprocessor:
1.	Fetching and execution operations can be pipelined.
2.	Powerful instruction sets are used.
3.	Can perform more complicated arithmetic and logical operations.
4.	High speed

6. Disadvantages of 8086 Microprocessor
  1. 8086 has no hardware support for virtual memory.
  2. One of its disadvantages was 0that it was having segmented addressing modes.
Conclusion: History and evoluation of microprocessors was studied successfully