Flexibility to CARRY Laptops

A personal computer designed for mobile use, which is small enough to sit on a lap is called the laptop. A laptop integrates all components of a typical desktop computer, including a display, keyboard, a pointing device and a portable battery in one unit. Rechargeable battery is charged from an AC / DC adapter and has enough capacity to power a laptop for several hours. A laptop is usually shaped like a large notebook with thickness of 0.7-1.5 inches from 10x8 inches to 15x11 cm.

Modern laptops are designed with less weight to carry with flexibility. Most laptops are designed in the flip form factor to protect the screen and keyboard when closed. Of all, the sale of the laptops or computers is unbelievable. Advances in technology help users keep in touch with the workplace and the world around them. To impress users, laptop manufacturers keep updated version come with a tune-up with the latest technology. Undoubtedly updated laptops with advanced technology.

Now offered at low prices, flexibility for people with discounts. Laptops are the industry leader, with their performance and their term of validity. Now you can get door to Laptop via online.

Latest version of Laptops

Dell Inspiron 1525
The latest laptop Inspison is in line 1525. LCD panel on the 1525 is a good thing, and offers decent levels of contrast, color and brightness levels.

My HP 1000 Mini Edition

It looks cool, low-cost net book focuses on easy web access and entertainment. The design of laptops with more efficient and providing less cost, with special discounts to attract people.

CD-ROM Format

A CD-ROM sector contains 2352 bytes, divided into 98 24-byte frames. The CD-ROM is, in essence, a data disk, which cannot rely on error concealment, and therefore requires a higher reliability of the retrieved data. In order to achieve improved error correction and detection, a CD-ROM has a third layer of Reed-Solomon error correction. A Mode-1 CD-ROM, which has the full three layers of error correction data, contains a net 2048 bytes of the available 2352 per sector. In a Mode-2 CD-ROM, which is mostly used for video files, there are 2336 user-available bytes per sector. The net byte rate of a Mode-1 CD-ROM is 44.1k×2048/(6×98) = 153.6 kB/s. The playing time is 74 minutes, or 4440 seconds, so that the net capacity of a Mode-1 CD-ROM is 682 MB.
A 1x speed CD drive reads 75 consecutive sectors per second.

CD-ROM

CD-ROM ("Compact Disc read-only memory" or "Compact Disc read-only media") is a Compact Disc that contains data accessible by a computer. While the Compact Disc format was originally designed for music storage and playback, the format was later adapted to hold any form of binary data. CD-ROMs are popularly used to distribute computer software, including games and multimedia applications, though any data can be stored (up to the capacity limit of a disc). Some CDs hold both computer data and audio with the latter capable of being played on a CD player, whilst data (such as software or digital video) is only usable on a computer. These are called Enhanced CDs.

Although many people use lowercase letters in this acronym, proper presentation is in all capital letters with a hyphen between CD and ROM. It is also debated whether the correct terminology is read-only memory or media. It is generally accepted that, in technical terms, media is the correct terminology. However, due to the widespread use of ROM to refer to other devices such as EEPROM and Flash-ROM (where memory is the correct terminology) most people define CD-ROM as also being memory as it sounds like the abbreviation is from the same origin.

Peripheral

A peripheral is a type of computer hardware that is added to a host computer in order to expand its abilities. More specifically, the term is used to describe those devices that are optional in nature, as opposed to hardware that is either demanded or always required in principle.

The term also tends to be applied to devices that are hooked up externally, typically through some form of computer bus like USB. Typical examples include joysticks, printers and scanners. Devices such as monitors and disk drives are not considered peripherals when they are not truly optional, and video capture cards are typically not referred to as peripheral because they are internal devices.

DIMM Ranking

The number of ranks on any DIMM is the number of independent sets of DRAMs that can be accessed simultaneously for the full data bit-width of the DIMM to be driven on the bus. The physical layout of the DRAM chips on the DIMM itself does not necessarily relate to the number of ranks. Sometimes the layout of all DRAM on one side of the DIMM PCB versus both sides is referred to as "single-sided" versus "double-sided".

These terms may cause confusion as they do not necessarily relate to how the DIMMs are logically organized or accessed.

For example, on a single rank DIMM that has 64 data bits of I/O pins, there is only one set of DRAMs that are turned on to drive a read or receive a write on all 64-bits. In most electronic systems, memory controllers are designed to access the full data bus width of the memory module at the same time.

On a 64-bit (non-ECC) DIMM made with two ranks, there would be two sets of DRAM that could be accessed at different times. Only one of the ranks can be accessed at a time, since the DRAM data bits are tied together for two loads on the DIMM (Wired OR). Ranks are accessed through chip selects (CS). Thus for a two rank module, the two DRAMs with data bits tied together may be accessed by a CS per DRAM (e.g. CS0 goes to one DRAM chip and CS1 goes to the other). DIMMs are currently being commonly manufactured with up to four ranks per module.

Consumer DIMM vendors have recently begun to distinguish between single and dual ranked DIMMs. JEDEC decided that the terms "dual-sided," "double-sided," or "dual-banked" were not correct when applied to registered DIMMs.

Dual In-line Memory Module DIMM

A DIMM, or dual in-line memory module comprises a series of random access memory integrated circuits. These modules are mounted on a printed circuit board and designed for use in personal computers. DIMMs began to replace SIMMs (single in-line memory modules) as the predominant type of memory module as Intel's Pentium processors began to control the market.

The main difference between SIMMs and DIMMs is that SIMMs have a 32-bit data path, while DIMMs have a 64-bit data path. Since Intel's Pentium has (as do several other processors) a 64-bit bus width, it required SIMMs installed in matched pairs in order to use them. The processor would then access the two SIMMs simultaneously. DIMMs were introduced to eliminate this inefficiency. Another difference is that DIMMs have separate electrical contacts on each side of the module, while the contacts on SIMMs on both sides are redundant.
The most common types of DIMMs are:

72-pin-DIMMs, used for SO-DIMM
144-pin-DIMMs, used for SO-DIMM
200-pin-DIMMs, used for SO-DIMM
168-pin-DIMMs, used for FPM, EDO and SDRAM
184-pin-DIMMs, used for DDR SDRAM
240-pin-DIMMs, used for DDR2 SDRAM

There are 2 notches on the bottom edge of 168-pin-DIMMs, and the location of each notch determines a particular feature of the module.

The first notch is DRAM key position. It represents RFU (reserved future use), registered, and unbuffered.

The second notch is voltage key position. It represents 5.0V, 3.3V, and Reserved.

The upper DIMM in the photo is an unbuffered 3.3V 168-pin DIMM. A DIMM's capacity and timing parameters may be identified with SPD (Serial Presence Detect), an additional chip which contains information about the module type.

ECC DIMMs are those that have extra data-bits which can be used by the system memory controller to detect and correct errors. There are numerous ECC schemes, but perhaps the most common is Single Error Correct, Double Error Detect (SECDED) which uses a 9th extra bit per byte.

Synchronous Graphics RAM (SGRAM)

SGRAM is a specialized form of SDRAM for graphics adaptors. It adds functions such as bit masking (writing to a specified bit plane without affecting the others) and block write (filling a block of memory with a single colour). Unlike VRAM and WRAM, SGRAM is single-ported. However, it can open two memory pages at once, which simulates the dual-port nature of other video RAM technologies.

SGRAM and SDRAM became the most popular types of DRAM at the end of the 1990s, and well into the first decade of the 2000s.

Burst EDO (BEDO) DRAM

An evolution of the former, Burst EDO DRAM, could process four memory addresses in one burst, for a maximum of 5-1-1-1, saving an additional three clocks over optimally designed EDO memory. It was done by adding an address counter on the chip to keep track of the next address. BEDO also added a pipelined stage allowing page-access cycle to be divided into two components. During a memory-read operation, the first component accessed the data from the memory array to the output stage (second latch). The second component drove the data bus from this latch at the appropriate logic level. Since the data is already in the output buffer, faster access time is achieved (up to 50% for large blocks of data) than with traditional EDO.
Although BEDO DRAM showed additional optimization over EDO, by the time it was available, the market had made a significant investment towards synchronous DRAM, or SDRAM, even though BEDO RAM was technically superior to SDRAM.

Extended Data Out (EDO) DRAM

EDO DRAM is similar to Fast Page Mode DRAM with the additional feature that a new access cycle can be started while keeping the data output of the previous cycle active. This allows a certain amount of overlap in operation (pipelining), allowing somewhat improved speed. It was 5% faster than Fast Page Mode DRAM, which it began to replace in 1993.

Single-cycle EDO has the ability to carry out a complete memory transaction in one clock cycle. Otherwise, each sequential RAM access within the same page takes two clock cycles instead of three, once the page has been selected. EDO's speed and capabilities allowed it to somewhat replace the then-slow L2 caches of PCs. It created an opportunity to reduce the immense performance loss associated with a lack of L2 cache, while making systems cheaper to build. This was also good for notebooks due to difficulties with their limited form factor, and battery life limitations. An EDO system with L2 cache was tangibly faster than the older FPM/L2 combination.

Single-cycle EDO DRAM became very popular on video cards towards the end of the 1990s. It was very low cost, yet nearly as efficient for performance as the far more costly VRAM.
EDO was sometimes referred to as Hyper Page Mode.

Window RAM or WRAM

Window RAM or WRAM is an obsolete type of semiconductor computer memory that was designed to replace video RAM (VRAM) in graphics adapters. It was developed by Samsung and also marketed by Micron Technology, but had only a short market life before being superseded by SDRAM and SGRAM.

WRAM has a dual-ported dynamic RAM structure similar to that of VRAM, with one parallel port and one serial port, but has extra features to enable fast block copies and block fills (so-called window operations). It was often clocked at 50 MHz. It has a 32-bit wide host port to enable optimal data transfer in PCI and VESA Local Bus systems. Typically WRAM was 50% faster than VRAM, but with costs 20% lower. It is sometimes erroneously called Windows RAM, because of confusion with the Microsoft Windows operating systems, to which it is unrelated apart from the fact that window operations could boost the performance of windowing systems.

Video DRAM (VRAM)

VRAM is a dual-ported version of DRAM formerly used in graphics adaptors. It is now almost obsolete, having been superseded by SDRAM and SGRAM. VRAM has two paths (or ports) to its memory array that can be used simultaneously.

The first port, the DRAM port, is accessed as with plain DRAM. The second port, the video port, is read-only, and is dedicated to feeding a fast stream of data to the display. To use the video port, the controller first uses the DRAM port to select the row of the memory array that is to be displayed. The VRAM then copies that entire row to an internal shift-register. The controller can then continue to use the DRAM port for drawing objects on the display. Meanwhile, the controller feeds a clock called the shift clock (SCLK) to the VRAM's video port. Each SCLK pulse causes the VRAM to deliver the next item of data, in strict address order, from the shift-register to the video port. For simplicity, the graphics adapter is usually designed so that the contents of a row, and therefore the contents of the shift-register, corresponds to a complete horizontal line on the display.

How Dynamic Random Access Memory (DRAM) Works

DRAM is usually arranged in a square array of one capacitor and transistor per cell. The illustrations above show a simple example with only 4 by 4 cells (modern DRAM can be thousands of cells in length/width). A read operation proceeds as follows: the row of the selected cell is activated, turning on the transistors and connecting the capacitors of that row to the sense lines. The sense lines lead to the sense amplifiers, which distinguish signals that represent a stored 0 or 1. The amplified value from the appropriate column is then selected and connected to the output. At the end of a read cycle, the row values must be restored to the capacitors, which were depleted during the read. A write operation is done by activating the row and connecting the values to be written to the sense lines, which charges the capacitors to the desired values. During a write to a particular cell, the entire row is read out, one value changed, and then the entire row is written back in, as illustrated in the figure to the right.

Typically, manufacturers specify that each row should be refreshed every 64 ms or less, according to the JEDEC standard. Refresh logic is commonly used with DRAMs to automate the periodic refresh. This makes the circuit more complicated, but this drawback is usually outweighed by the fact that DRAM is much cheaper and of greater capacity than SRAM. Some systems refresh every row in a tight loop that occurs once every 64 ms. Other systems refresh one row at a time -- for example, a system with 213 = 8192 rows would require a refresh rate of one row every 7.8 µs (64 ms / 8192 rows). A few real-time systems refresh a portion of memory at a time based on an external timer that governs the operation of the rest of the system, such as the vertical blanking interval that occurs every 10 to 20 ms in video equipment. All methods require some sort of counter to keep track of which row is the next to be refreshed. Some DRAM chips include that counter; other kinds require external refresh logic to hold that counter. (Under some conditions, most of the data in DRAM can be recovered even if the DRAM has not been refreshed for several minutes.

Dynamic Random Access Memory (DRAM)

Dynamic random access memory (DRAM) is a type of random access memory that stores each bit of data in a separate capacitor within an integrated circuit. Since real capacitors leak charge, the information eventually fades unless the capacitor charge is refreshed periodically. Because of this refresh requirement, it is a dynamic memory as opposed to SRAM and other static memory. Its advantage over SRAM is its structural simplicity: only one transistor and a capacitor are required per bit, compared to six transistors in SRAM. This allows DRAM to reach very high density. Since DRAM loses its data when the power supply is removed, it is in the class of volatile memory devices.

Random Access Memory RAM

Random access memory (usually known by its acronym, RAM) is a type of data store used in computers that allows the stored data to be accessed in any order — that is, at random, not just in sequence. In contrast, other types of memory devices (such as magnetic tapes, disks, and drums) can access data on the storage medium only in a predetermined order due to constraints in their mechanical design.

It costs practically the same time to access any piece of data stored in a RAM chip. In contrast, disks and the like need a short time to retrieve a piece of data if it happens to be close to the current position of the read head, and a long time if the data is far away and the head needs to be repositioned considerably.

Generally, RAM in a computer is considered main memory or primary storage: the working area used for loading, displaying and manipulating applications and data. This type of RAM is usually in the form of integrated circuits (ICs). These are commonly called memory sticks or RAM sticks because they are manufactured as small circuit boards with plastic packaging and are about the size of a few sticks of chewing gum. Most personal computers have slots for adding and replacing memory sticks.

Most RAM can be both written to and read from, so "RAM" is often used interchangeably with "read-write memory." In this sense, RAM is the "opposite" of ROM, but in a more true sense, of sequential access memory.

Laptop

A laptop computer or simply laptop (also notebook computer or notebook or labtop) is a small mobile computer, which usually weighs 2.2-12 pounds (1-6 kilograms), depending on size, materials and other factors.

While the terms laptop and notebook are often used interchangeably, "laptop" is the older term, introduced in 1983 with the Gavilan SC. "Notebook computer" is a later coinage, which was used to differentiate smaller devices such as those of the NEC UltraLite and Compaq LTE series in 1989, which were, in contrast to previous laptops, the approximate size of an A4 paper sheet.[1] The terms are imprecise: due to heat and other issues, many laptops are inappropriate for use on one's lap, and most notebooks are not the size of typical A4 paper notebook. Although some older portable computers, such as the Macintosh Portable and certain Zenith TurbosPort models, were sometimes described as "laptops", their size and weight were too great for this category.

Laptops usually run on a single battery or from an external AC/DC adapter which can charge the battery while also supplying power to the computer itself.
As personal computers, laptops are capable of the same tasks as a desktop PC, although they are typically less powerful for the same price. They contain components that are similar to their desktop counterparts and perform the same functions, but are miniaturized and optimized for mobile use and efficient power consumption. Laptops usually have liquid crystal displays and most of them use different memory modules for their random access memory (RAM), for instance, SO-DIMM in lieu of the larger DIMMs. In addition to a built-in keyboard, they may utilize a touchpad (also known as a trackpad) or a pointing stick for input, though an external keyboard or mouse can usually be attached.