Primary & Secondary Memory, Lecture notes of Computer Science

Download Primary & Secondary Memory and more Lecture notes Computer Science in PDF only on Docsity! wv O @ Mm Dm g a = rFlOC Lazirning OF In this chapter you will learn about: Internal structure of processor Memory structure Determining the speed of a processor Different types of processors available Determining the capacity of a memory Different types of memory available MDD MD MD MD MH Several other terms related to the processor and main memory of a computer system One of the two basic components of CPU Acts as the central nervous system of a computer system Selects and interprets program _ instructions, and coordinates execution Has some special purpose registers and a decoder to perform these activities Mm MD MD OM One of the two basic components of CPU. Actual execution of instructions takes place in ALU Has some special purpose registers Has necessary circuitry to carry out all the arithmetic and logic operations included in the CPU instruction set CPU has built-in ability to execute a particular set of machine instructions, called its instruction set Most CPUs have 200 or more instructions (such as add, subtract, compare, etc.) in their instruction set CPUs made by different manufacturers have different instruction sets Manufacturers tend to group their CPUs into “families” having similar instruction sets New CPU whose instruction set includes instruction set of its predecessor CPU is said to be backward compatible with its predecessor Computer has a built-in system clock that emits millions of regularly spaced electric pulses per second (known as clock cycles) It takes one cycle to perform a basic operation, such as moving a byte of data from one memory location to another Normally, several clock cycles are required to fetch, decode, and execute a single program instruction Hence, shorter the clock cycle, faster the processor Clock speed (number of clock cycles per second) is measured in Megahertz (10° cycles/sec) or Gigahertz (10° cycles/sec) Type of Architecture Features Usage CISC (Complex Instruction Set Com puter) § Large instruction set § Variable-length instructions § Variety of addressing modes § Complex & expensive to produce Mostly used in personal computers RISC (Reduced Instruction Set Com puter) § Small instruction set § Fixed-length instructions § Reduced references to memory to retrieve operands Mostly used in workstations (Continued on next slide) (Continued from previous slide..) Type of Architecture Features Usage EPIC (Explicitly Parallel Instruction Computing) § Allows software to communicate explicitly to the processor when operations are parallel § Uses tighter coupling between the compiler and the processor § Enables compiler to extract maximum parallelism in the original code, and explicitly describe it to the processor Mostly used in high-end servers and workstations (Continued on next slide) . Primary Secondary Property Desirable storage storage Storage . capacity Large storage capacity Small Large Access Time Fast access time Fast Slow Cost per bit of Lower cost per bit High Low storage Volatility Non-volatile Volatile Non-volatile Pseudo- random Random Access Random access access or access : sequential access Addresses of a memory < Vd | N-2—>+ N-1—> NX Bit 1 Bit 2 rd [— The words of a memory (total N words) Each word contains the same number of bits = word length (Continued on next slide) (Continued from previous slide..) § Machines having smaller word-length are slower in operation than machines having larger word-length § A write to a memory location is destructive to its previous contents § A read from a memory location is non-destructive to its previous contents § Memory capacity of a computer is equal to the number of bytes that can be stored in its primary storage § Its units are: Kilobytes (KB) : 1024 (21°) bytes Megabytes (MB) : 1,048,576 (22°) bytes Gigabytes (GB) : 1,073,741824 (23°) bytes Primary storage of a computer is often referred to as RAM because of its random access capability RAM chips are volatile memory A computer’s motherboard is designed in a manner that the memory capacity can be enhanced by adding more memory chips The additional RAM chips, which plug into special sockets on the motherboard, are known as single-in-lineé memory modules (SIMMs) § ROM anon-volatile memory chip § Data stored in a ROM can only be read and used — they cannot be changed § ROMs are mainly used to store programs and data, which do not change and are frequently used. For example, system boot program § It is commonly used for minimizing the memory- processor speed mismatch. § It is an extremely fast, small memory between CPU and main memory whose access time is closer to the processing speed of the CPU. § It is used to temporarily store very active data and instructions during processing. Cache is pronounced as “cash” § Accumulator Register (AR) § Address § Arithmetic Logic Unit (ALU) § Branch Instruction § Cache Memory § Central Processing Unit (CPU) § CISC (Complex Instruction Set Computer) architecture § Clock cycles § Clock speed § Control Unit § Electrically EPROM (EEPROM) § Erasable Programmable Read- Only Memory (EPROM) § Explicitly Parallel Instruction Computing (EPIC) § Fixed-word-length memory § Flash Memory § Input/Output Register (I/O) § Instruction Register (1) § Instruction set § Kilobytes (KB) § Main Memory § Manufacturer-Programmed ROM § Megabytes (MB) § Memory § Memory Address Register (MAR) § Memory Buffer Register (MBR) § Microprogram § Multi-core processor § Non-Volatile storage Processor § Program Control Register (PC) § Programmable Read-Only Memory (PROM) § Random Access Memory (RAM) (Continued on next slide) (Continued from previous slide..) § Read-Only Memory (ROM) § Register § RISC (Reduced Instruction Set Computer) architecture § Single In-line Memory Module (SIMM) § Ultra Violet EPROM (UVEPROM) § Upward compatible § User-Programmed ROM § Variable-word-length memory § Volatile Storage § Word length § Word size