EC 6009 ADVANCED COMPUTER ARCHITECTURE UNIT I FUNDAMENTALS

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EC 6009 ADVANCED COMPUTER ARCHITECTURE UNIT I FUNDAMENTALS OF COMPUTER DESIGN Review of fundamentals

EC 6009 ADVANCED COMPUTER ARCHITECTURE UNIT I FUNDAMENTALS OF COMPUTER DESIGN Review of fundamentals of CPU, Memory and IO Trends in Technology, Power, Energy and Cost, Dependability- Performance Evaluation.

INTRODUCTION • 65– 70 years back the first general purpose electronic computer was created.

INTRODUCTION • 65– 70 years back the first general purpose electronic computer was created. • Today less than $500 mobile computer that has more performance, more main memory and more disk storage than a computer in 1985 for $1 million. • This rapid improvement has come both from advances in the technology used to build computers and from innovations in computer design. • RISC based machine focused on two critical performance techniques. Exploitation of Instruction Level Parallelism (initially through pipelining and later through multiple instruction issue) Use of Caches. • For many applications, the highest performance microprocessors of today outperform the supercomputer of less than 10 years ago. • Dramatic improvement in cost-performance leads to new classes of computers.

INTRODUCTION • • • The last decade saw the rise of smart cell phones

INTRODUCTION • • • The last decade saw the rise of smart cell phones and tablet computers, which are many people are using as their primary computing platform instead of PCs. These mobile client devices are increasingly using the internet to access warehouses containing tens of thousands of servers. Mainframe computers and high performance Supercomputers all are collections of microprocessors. Today the nature of application also changes. Speech, sound, images and videos are becoming increasingly important along with predictable response time that is so critical to the user experience. An inspiring example is Google Goggles. This application lets you hold up your cell phone to point its camera at an object, and the image is sent wirelessly over the internet to a WSC that recognize the object and tells you interesting information about it. Read the bar code on a book cover to tell you if a book is available online and its price. Since 2003, single-processor performance improvement has dropped to less than 22% per year due to the twin hurdles of maximum power dissipation and the lack of more ILP. In 2004, Intel canceled its high-performance uniprocessor projects and joined others in declaring that the road to higher performance would be via multiple processors per chip rather than via faster uniprocessors.

REVIEW OF FUNDAMENTALS OF CPU The functional blocks in a computer are 1. ALU

REVIEW OF FUNDAMENTALS OF CPU The functional blocks in a computer are 1. ALU 2. Control Unit 3. Memory 4. Input Unit 5. Output Unit The ALU contains necessary electronic circuits to perform arithmetic and logical operations. • The Control Unit analyses each instruction in the program and sends the relevant control Signals to all other units – ALU, Memory, Input and Output Unit. • The program is fed into the computer through the input unit and stored in the memory. In order to execute the program, the instructions have to be fetched from memory one by one. This fetching of instruction is done by the control unit. • After an instruction is fetched, the control unit decodes the instruction. According to the instruction, the control unit issues control signals to other units. • After an instruction is executed, the result of the instruction is stored in memory or stored temporarily in the control unit or ALU, so that this can be used by the next instruction. • The results of a program are taken out of the computer through the output unit. • The control unit and ALU are collectively known as Central Processing Unit (CPU). •

REVIEW OF FUNDAMENTALS OF CPU The physical units in a computer such as the

REVIEW OF FUNDAMENTALS OF CPU The physical units in a computer such as the CPU, Memory, Input and Output units form the Hardware. • The Compilers as well as user programs (high level language or machine language) form the software. • Hardware works as dictated by the software. The operating system is a special software that manages the H/W and S/W. Arithmetic and Logic Unit: The ALU has hardware circuits which perform primitive arithmetic and logical operations. The H/W sections in ALU are 1. Adder 2. Accumulator 3. General Purpose Register 4. Counters 5. Shifters 6. Complementer. Adder: adds two numbers and gives the result. Accumulator: Register which temporarily holds the results of a previous operation in the ALU. •

REVIEW OF FUNDAMENTALS OF CPU General Purpose Register: When an operand is stored in

REVIEW OF FUNDAMENTALS OF CPU General Purpose Register: When an operand is stored in main memory, it takes time to retrieve it. If it is stored within the CPU, it is immediately available to the CPU. The GPR’s store different types of information 1. Operand 2. Operand address 3. Constant Since they are used for multiple purposes, these registers are known as GPR’s. Scratch Pad Memory or Registers: During Complex operations like multiplication, division etc. , it is necessary to store intermediate results temporarily. For this purpose there are usually one or more scratch pad registers. These are purely internal H/W resources and not addressable by program. Shifter and Complementer: The shifter provides left and right shift required for various operations. The complementer provides 2’s complement of binary numbers.

REVIEW OF FUNDAMENTALS OF CPU CONTROL UNIT: The control unit is the most complex

REVIEW OF FUNDAMENTALS OF CPU CONTROL UNIT: The control unit is the most complex unit in a computer. Its main functions are 1. Fetching instructions 2. Analyzing the OPCODE 3. Generating control signals for performing various operations. H/W resources of a control unit: Program Counter or Instruction Address Counter (IAC): IAC contains the memory address of the next instruction to be fetched. When an instruction is fetched, the IAC is incremented so that it points to the address of the next instruction. Every instruction contains an opcode. In addition it may contain one or more of the following. 1. Operand 2. Operand address 3. Register address PSW Register : It contains various status bits describing the current condition of the CPU. These are known as flags. Two such flags are 1. Interrupt Enable: When this bit is 1, CPU will recognize interrupt requests. When this bit is 0, interrupt requests will be ignored by the CPU and they remain pending. The

MEMORY AND IO The Memory is organized in to locations. Each memory location is

MEMORY AND IO The Memory is organized in to locations. Each memory location is known as one memory Word. Memory Types: Older computers use magnetic core memory while the present day we use Semiconductor Memory. Core memory is non-volatile where semiconductor memory is volatile. semiconductor memory is of two types: SRAM and DRAM. SRAM preserves the contents of all the locations as long as the power supply is present. DRAM memory can retain the content of any location only for a few milliseconds. Random Access and Sequential Access Memories: In a RAM access time is same for all locations. (Core and Semiconductor Memories are RAM) In a sequential access memory, the read or write access is sequential. The time taken For accessing the first location is the shortest and the time taken for the last location is the Longest. ( Magnetic tape)

MEMORY AND IO Memory Organization: The Memory unit consists of the following sections: 1.

MEMORY AND IO Memory Organization: The Memory unit consists of the following sections: 1. Memory Address Register (MAR) 2. Memory Data Register (MDR) 3. Memory Control Logic 4. Memory cells For the read operation, the CPU does the following sequence: (i) Sends the address to MAR. (ii) Sends READ signal to memory control unit. The Memory control unit decodes the address bits and identifies the location to be accessed. Then it initiates a read operation of the memory. The memory takes some amount of time to present the contents of the location in MDR. (iii) After a sufficient time interval, the CPU transfers the information from MDR.

MEMORY AND IO For Write operation, the CPU does the following sequence: (i) Sends

MEMORY AND IO For Write operation, the CPU does the following sequence: (i) Sends address to MAR. (ii) Sends data to MDR. (iii) Sends WRITE signal to memory control unit. The Memory control unit decodes the address bits and identifies the location Where the write operation has to be performed. It then routes the MDR Contents to memory and initiates the write operation. Memory Access Time: The time taken by the memory to supply the contents of a location , from the time it receives ‘Read’ is called the Memory Access time. Core Memory 800 ns and semiconductor memory 100 ns. Memory Cycle Time: The memory access time plus the additional recovery Time (memory is busy due to internal operation) is known as Memory Cycle time. Auxiliary Memory: 1. Floppy Disk drive 2. Hard Disk drive 3. Magnetic tape drive 4. CD-ROM. Input / Output Units: Common input units are Keyboard, floppy disk, hard disk, magnetic tape,