M.Tech (C.S.E)

Wednesday, 26 October 2016

Cache Memory

02:09

Cache Memory: - Cache memory is one of the fast and small memory. It is placed between the CPU and main memory. The access time of cache memory is less than main memory by the factor of 5 to 10. Cache is the fastest component in the memory hierarchy and approaches the speed of CPU components. The operation of cache memory is as follows: When CPU needs access memory. The cache is examined. If the word is found in the cache it is accessed from cache memory. If word is no found in the cache memory, then it is accessed from main memory.

The performance of cache memory is frequently measured in terms of quantity called hit ratio. When CPU refers to memory and finds the word in cache, it is said to produce a hit. If the word is not found in cache, it is in the main memory and it counts as a miss. The basic characteristics of cache memory is its fast access time.

Mapping: - The transformation of data from main memory to cache memory is referred to as a mapping process. Each memory address maps to exactly one set in the cache. Some of the address bits are used to determine which cache set contains the data. If the set contains more than one block, the data may be kept in any of the blocks in the set.

Three types of mapping procedures are of practical interest when considering the organization of cache memory:

Associative mapping
Direct mapping
Set-associative mapping

Associative mapping: - The fastest and most flexible cache organization uses an associative memory. The associative mapping stores both the address and data of the memory word. This permits any location in cache to store any word from main memory.

Caches are classified as either write-through cache or write-back cache. Modern caches are usually write-back, because main memory access time is so large.

· In a write through cache, the data written to a cache block is simultaneously written to main memory. A write-through cache requires no dirty bit but usually requires more main memory writes

· In a write-back cache, a dirty bit (D) is associated with each cache block

Fundamental of Memory

01:08

The Memory unit is an essential component in any digital computer. Memory is needed for storing programs and data. The total memory capacity of a computer can be visualized as being a hierarchy of components. The memory hierarchy system consists of all storage devices employed in computer system from the slow but high capacity auxiliary memory to a relatively faster main memory.

The memory unit that directly communicate with CPU is called Main Memory. Only programs and data currently needed by the processor reside in main memory.

Devices that provides backup storage called auxiliary memory. The most common auxiliary devices used in computer system are magnetic disks and tapes. They are used for storing system programs, large data files, and other backup information.
All other information is stored in auxiliary memory and transferred to main memory when needed.

Very high speed memory is called Cache Memory. It is used to increase the speed of processing by making current programs and data available to the CPU at a rapid rate. CPU logic is usually faster than main memory access time. The cache is used for storing segments of programs currently being executed in the CPU and temporary data frequently needed in the present calculations. Cache organization is concerned with the transfer of information between main memory and CPU.

Cache memory is: -

· Very small.

· Relatively expensive.

· and has very high access speed.

· Cache memory holds those parts that are not presently used by the CPU.

Main Memory: - Main memory is central storage unit in computer system. The principal technology used for the main memory is based on semiconductor integrated circuits. Integrated circuits RAM chips are available in two possible operating modes, static and dynamic. Main memory is: -

· Fast.

· Relatively large.

· And used to store programs and data during the computer operations.

The static RAM consist of internal flip-flops that store the binary information. The stored information remains valid as long as power is applied to the unit. Static RAM is easier to use and has shorted read and writes cycles.

The dynamic RAM stores the binary information in the form of electric charges that are applied to capacitors. The capacitors are provided inside the chip by MOS transistors. The dynamic RAM offers reduced power consumption and larger storage capacity in single memory chip. The dynamic RAM’s are used to for implementing the main memory. Most of the computer systems are dynamic RAMs with improved performance characteristics such as multi-bank DRAM, synchronous DRAM, and Direct DRAM bus DRAM.

Memory Connections to CPU: - RAM and ROM chips are connected to CPU through the data and address buses. The data bus of ROM has only one output capacity, whereas the data bus connected to RAMs can transfer information in both directions.

Monday, 17 October 2016

Mini Project in HTML,CSS and JS

05:11

DESKTOP GADGETS: MINI-PROJECT IS CREATED BY USING HTML, CSS & JAVA-SCRIPT

This mini project is created by using web-development languages such as HTML, CSS and java script.We can create simple and dynamic projects by using scripting languages. In this mini-project i use simple html tags like <html>,<head>,<div>,<body>,<img>,<br>,<link>,<a>,<font>,<header>,<footer>,<aside>. In CSS, i use separate style sheet and linked that style sheet in html page.In javaScript, i use simple dialogs for admin and user passwords.