Modelling Of Modern Microprocessors

Siddhant (Author)
Department of Computer Science
Lovely Professional University
Phagwara, India siddhant_s@outlook.com Abstract--Microprocessors are also known as a CPU or central processing unit is a complete computation engine that is fabricated on a single chip. The first microprocessor was the
Intel 4004, introduced in 1971. This paper covers the evolution in microprocessors and the changes in the architecture of the microprocessor, the details of the latest microprocessors and the machines using them.
The paper also discusses how the number of transistors affects the performance of processor. 


A microprocessor can move data from one memory location to another.
A microprocessor can make decisions and jump to a new set of instructions based on those decisions.

The native language of a microprocessor is
Assembly Language. The above mentioned are the three basic activities of a microprocessor. An extremely simple microprocessor capable of performing the above mentioned operations loos like: Index terms—Modern, architecture, Intel, PC, Apple.

I. INTRODUCTION
The microprocessor is the heart of any normal computer, whether it is a desktop machine , a server or a laptop . The first microprocessor to make a real splash in the market was the Intel 8088, introduced in 1979 and incorporated into the IBM PC
(which first appeared around 1982).The microprocessor is made up of transistors. CHIPA chip is also called an integrated circuit. Generally it is a small, thin piece of silicon onto which the transistors making up the microprocessor have been fixed. A chip might be as large as an inch on a side and can contain tens of millions of transistors.
Simpler processors might consist of a few thousand transistors fixed onto a chip just a few millimeters square. A microprocessor is a device that executes a collection of machine instructions that tell the processor what to do. Based on the instructions, a microprocessor does three basic things:
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Using its ALU (Arithmetic/Logic Unit), a microprocessor can perform mathematical operations like addition, subtraction, multiplication and division. Modern microprocessors contain complete floating point processors that can perform extremely sophisticated operations on large floating point numbers.

the components of this simple microprocessor:
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
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Registers A, B and C are simply latches made out of flip-flops.
The address latch is just like registers A, B and C.
The when told to do so, and also to reset to zero program counter is a latch with the extra ability to increment by 1when told to do so.

Modelling Of Modern Microprocessors
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The ALU could be as simple as an 8-bit adder, or it might be able to add, subtract, multiply and divide 8-bit values. We will assume the latter here.

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The test register is a special latch that can hold values from comparisons performed in the ALU. An ALU can normally compare two numbers and determine if they are equal, if one is greater than the other, etc.
The test register can also normally hold a carry bit from the last stage of the adder. It stores these values in flip-flops and then the instruction decoder can use the values to make decisions.



There are 6 boxes marked "3-State" in the diagram. These are tri-state buffers. A tristate buffer can pass a 1, a 0 or it can essentially disconnect its output (imagine a switch that totally disconnects the output line from the wire the output is heading toward). A tri-state buffer allows multiple outputs to connect to a wire, but only one of them to actually drive a 1 or a 0 onto the line. The instruction register and instruction decoder are responsible for controlling all of the other components.

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Even the incredibly simple microprocessor shown in the previous example will have a fairly large set of instructions that it can perform. The collection of instructions is implemented as bit patterns, each one of which has a different meaning when loaded into the instruction register. Humans are not particularly good at remembering bit patterns, so a set of short words are defined to represent the different bit patterns.
This collection of words is called the assembly language of the processor. An assembler can translate the words into their bit patterns very easily, and then the output of the assembler is placed in memory for the microprocessor to execute. II. PERFORMANCE
Reduced instruction set computing or RISC is a CPU design strategy based on the insight that simplified (as opposed to complex) instructions can provide higher performance if this simplicity enables much faster execution of each instruction. A computer based on this strategy is a reduced instruction set computer, also called RISC.
The opposing architecture is known as complex instruction set computing, i.e. CISC. "The number of transistors incorporated in a chip will approximately double every 24 months" forecasted
Gordon Moore-the co-founder of Intel Corp. The number of transistors available has a huge effect on the performance of a processor. A typical instruction in a processor like an 8088 took 15 clock cycles to execute. Because of the design of the multiplier, it took approximately 80 cycles just to do one 16-bit multiplication on the 8088. With more transistors, much more powerful multipliers capable of singlecycle speeds become possible.
More transistors also allow a technology called pipelining. In a pipelined architecture, instruction execution overlaps. So even though it might take 5 clock cycles to execute each instruction, there can be 5 instructions in various stages of execution simultaneously. That way it looks like one instruction completes every clock cycle.
Many modern processors have multiple instruction decoders, each with its own pipeline. This allows multiple instruction streams, which means more than one instruction can complete during each clock cycle.
This technique can be quite complex to implement, so it takes lots of transistors.
Fig 2.1- The Instruction flow of a sequential processor

Modelling Of Modern Microprocessors
Fig.2.2- The Instruction flow of a pipelined processor

could understand and execute series of operations. Thus the processor would come with a specific instruction ‘MUL’ in its instruction set. ‘MUL’ will loads the two values from

the memory into separate registers, multiplies the operands in the execution unit, and then stores the product in the appropriate location. So, the entire task of multiplying two numbers can be completed with one instruction:
MUL 1:3, 4:2
MUL is referred to as a "complex instruction" as it operates directly on the computer's memory banks and does not require the programmer to explicitly call any loading or storing functions.
RISC VS CISC – An Example of multiplication of two numbers in memory. Suppose that the main memory is divided into locations numbered from
(row) 1: (column) 1 to (row) 5: (column) 4. The execution unit is responsible for carrying out all computations. However, the execution unit can only operate on data that has been loaded into one of the four registers (A, B, C, or D). Let's say we want to find the product of two numbers - one stored in location 1:3 and another stored in location 4:2 and store back the result to 1:3

CISC Approach
CISC design would try to finish the task in the minimum possible instructions by implementing hardware which

RISC Approach
RISC processors use simple instructions that can be executed within a clock cycle. Thus, ‘MUL’ instruction will be divided into three instructions.
i)
"LOAD," which moves data from the memory bank to a register, ii) "PROD," which finds the product of two operands located within the registers, and iii) "STORE," which moves data from a register to the memory banks.
In order to perform the task, a programmer would need to code four lines of assembly:
LOAD A, 1:3
LOAD B, 4:2
PROD A, B
STORE 1:3, A
III. EVOLUTION
The first multi-chip 16-bit microprocessor was the
National Semiconductor IMP-16, introduced in early
1973. An 8-bit version of the chipset was introduced in 1974 as the IMP-8. During the same year, National introduced the first 16-bit single-chip microprocessor, the PACE (see the nearby photo), which was later followed by an NMOS version, the INS8900. The first single-chip 16-bit microprocessor was TI's TMS 9900, introduced in
1976, which was also compatible with their TI-990 line of minicomputers. Intel produced its first 16 bit processor, the 8086, in 1978. It was source compatible with the 8080 and 8085 (an 8080 derivative). This chip has probably had more effect on the present day computer market than any other, although whether this is justified is debatable; the

Modelling Of Modern Microprocessors chip was compatible with the 4 year old 8080 and this meant it had to use a most unusual overlapping segment register process to access a full 1 Megabyte of memory. The most significant of the 32-bit designs is the MC68000, introduced in 1979. The 68K, as it was widely known, had 32-bit registers but used 16bit internal data paths, and a 16-bit external data bus to reduce pin count, and supported only 24-bit addresses. Motorola generally described it as a 16-bit processor, though it clearly has 32-bit architecture.
The combination of high performance, large (16 megabytes (2^24)) memory space and fairly low costs made it the most popular CPU design of its class. The Apple Lisa and Macintosh designs made use of the 68000, as did a host of other designs in the mid-1980s, including the Atari ST and Commodore
Amiga.
The world's first single-chip fully-32-bit microprocessor, featuring 32-bit data paths, 32-bit buses, and 32-bit addresses, was the AT&T Bell Labs
BELLMAC-32A, with first samples in 1980, and general production in 1982 and the todays microprocessors known as the modern microprocessors are Intel core i3,i5 and i7 microprocessors used in every known PC.
Table 3.1- Exponential rise in number of transistors Microprocessor
8088
Pentium 4

Microarchitecture and cores
-----------------------------------------

Core i3(32nm)

Sandy Bridge,2

Core i3(22nm)

Haswell ,2

Core i5(22nm)

Sandy Bridge,4

Core i5(22nm)

Ivy Bridge,4

Core i7(22nm)

Sandy Bridge,4

Core i7(22nm)

Ivy Bridge,4

Core i7(22nm)

Ivy Bridge,6

No. of transistors 29,000
55
Million
624
Million
1.3
Billion
1.16
Billion
1.4
Billion
1.27
Billion
1.4
Billion
1.86
Billion

Sourcehttp://en.wikipedia.org/wiki/Transistor_count#Micro processors IV. REFERENCES
1.http://en.wikipedia.org/wiki/List_of_Intel_Core_i3
_microprocessors#.22Ivy_Bridge.22_.2822_nm.29_2
2.http://en.wikipedia.org/wiki/Transistor_count#Micr
oprocessors
3.http://www.intel.com/content/www/us/en/history/m
useum-gordon-moore-law.html
4. http://www.zenithindia.com/zen/TrainingMaterial/details/howmicropro cessorswork.htm 5. http://historycomputer.com/ModernComputer/Basis/microprocess or.html 6. https://illumin.usc.edu/printer/123/microprocessors-thesilicon-revolution/