2. MICRO-PROCESSORS

3. Objective To demonstrate How a Microprocessor do common calculations and the process involved in it. The type of calculations in which normally my class fellows do big mistakes.

4. Microprocessor But First Of All What a Microprocessor is? A microprocessor is also known as a CPU or Central Processing unit. It is a complete computation engine that is fabricated on a single chip. The first microprocessor was the Intel’s 4004, introduced in 1971. The 4004 was not very powerful, all it could do was to add and subtract, and it could only do that four bits at a time. But it was amazing that everything was on one chip. The 4004 powered one of the first portable electronic calculators. The first Microprocessor to make it into the house was Intel’s 8080, a complete 8-bit computer on one chip introduced in 1974. The first microprocessor to make a splash in the real market was the Intel’s 8088, introduced in 1979 and incorporated into the IBM Pc( which first appeared in 1982 or so).

5. In November 1971, Intel introduced the world's first commercial microprocessor, the 4004, invented by three Intel engineers. Primitive by today's standards, it contained a mere 2300 transistors and performed about 60,000 calculations in a second. Twenty five years later, the microprocessor is the most complex mass-produced product ever, with more than 5.5 million transistors performing hundreds of millions of calculations each second.

6. Pressing the 2 key alerts the microprocessor and signals the Prefetch Unit to ask the computer's main memory for a specific instruction on the new data since there is nothing about it in the Instruction Cache. The new data instruction comes into the microprocessor through the Bus Unit from the computer's main memory and gets stored in the Instruction Cache, where it is assigned a code "2=X".

7. The Prefetch Unit then asks the Instruction Cache for a copy of the code "2=X" and sends it to the Decode Unit for further processing. In the Decode Unit the instruction "2=X" is translated or decoded into a string of binary code that is sent off to the Control Unit and the Data Cache to tell them what to do with the instruction. Because the Decode Unit figured out that the number 2 was to be stored for the future in the Data Cache, the Control Unit now performs the instruction for "2=X." This causes the number 2 to be sent to an address in the Data Cache called "X," where you see it waiting for further orders.

8. When you press the 3 key the Pre-fetch Unit asks the computer's main memory and the Instruction Cache for specific instructions on this new data. No matching instruction is found in the Instruction Cache so the instruction will come from the main memory. Similar to "2=X," the new data instructions come into the microprocessor from the computer's main memory and get stored in an Instruction Cache address where it is assigned the code "3=Y."

9. The Prefetch Unit then pulls a copy of the code "3=Y" from the Instruction Cache and sends it to the Decode Unit for further processing. In the Decode Unit the instruction "3=Y" is translated or decoded into a string of binary code that is sent off to the Control Unit and the Data Cache to tell them what to do with the instruction. Because the Decode Unit figured out that the number 3 was to be stored for the future in the Data Cache, the Control Unit now performs the instruction for "3=Y." This causes the number 3 to be sent to an address in the Data Cache called "Y," where it waits like the "2" for further orders.

10. When you press the "+" key the Prefetch Unit asks the computer's main memory and Instruction Cache for instructions on the new data, which must be fetched from main memory Because this is a new instruction, the "+" comes into the microprocessor from the computer's main memory and gets stored at an address in the Instruction Cache as a code "X+Y=Z," showing that the act of adding is going to take place.

11. The Prefetch Unit then asks the Instruction Cache for a copy of the code "X+Y=Z" and sends it to the Decode Unit for further processing. In the Decode Unit, "X+Y=Z" is translated or decoded and sent off to the Control Unit and the Data Cache to tell them what to do with the instruction - also the ALU is given a message that an ADD function will be performed.

12. In the Control Unit the code is broken down and the ADD command is sent to the ALU where "X" and "Y" are added together after they have been sent up from the Data Cache. The ALU then talks to its buddy, the Registers, and sends the "5" over to be stored in one of the address locations there.

13. When you press the "=" key the Prefetch Unit once again checks the Instruction Cache for an instruction for the new data, which it doesn't find. The instruction for "=" comes into the microprocessor from the computer's main memory through the Bus Unit and gets stored in an Instruction Cache address as the code "Print Z."

14. The Prefetch Unit then asks the Instruction Cache for a copy of the code "Print Z" and sends it to the Decode Unit for further processing.. In the Decode Unit the instruction "Print Z" is translated or decoded into a string of binary code that is sent off to the Control Unit to tell it what to do with the instruction.

15. Now that the value of Z has been computed, and is residing in register file entry #5, the print command has only to retrieve register 5's contents and display them to a screen so you can finally see the sum of 2+3. The microprocessor has completed its task for you.

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17. Muhammad Zohair Imtiaz. CSU/F99/113 By: -

18. & Mujeeb Alam CSU/F99/121

19. Special Thanks To The Following. My Father Sabir Imtiaz. My Chacha Tariq Sarfaraz In US. Our friends In Which Rafia My Best Friend. Ibrahim Aslam(scharique).My Another Best Friend