Types of Computer HTypes of Computer Hard Disk Drivesard Disk Drives

Computer Hard Disk Drives

Computers rely on hard disk drives (HDDs) to store data permanently. They are storage devices used to save and retrieve digital information that will be required for future reference.

Hard drives are non-volatile, meaning that they retain data even when they do not have power. The information stored remains safe and intact unless the hard drive is destroyed or interfered with.

The information is stored or retrieved in a random access manner as opposed to sequential access. This implies that blocks of data can be accessed at any time they are required without going through other data blocks.

IBM 350 RAMAC, capacity 5Mb

The IBM 350 Disk File was developed under the code-name RAMAC by an IBM San Jose team led by Reynold Johnson | Source

Hard Disk Drives Has Stood the Test of Time

Hard disk drives were introduced in 1956 by IBM. At the time, they were being used with general purpose mainframes and minicomputers. Like other electronic devices, these have witnessed numerous technological advancements over the years. This is in terms of capacity, size, shape, internal structure, performance, interface, and modes of storing data.

These numerous changes have made HDDs here to stay, not like other devices that became obsolete the moment they are introduced in the market.

Hard Drive Types

Currently, we can group hard drives into four types:

• Parallel Advanced Technology Attachment (PATA)
• Serial ATA (SATA)
• Small Computer System Interface (SCSI)
• Solid State Drives (SSD)

Parallel Advanced Technology Attachment

These were the first types of hard disk drives and they made use of the Parallel ATA interface standard to connect to computers. These types of drives are the ones we refer to as Integrated Drive Electronics (IDE) and Enhanced Integrated Drive Electronics (EIDE) drives.

These PATA drives were introduced by Western Digital back in 1986. They provided a common drive interface technology for connecting hard drives and other devices to computers. Data transfer rate can go up to 133MB/s and a maximum of 2 devices can be connected to a drive channel. Most of the motherboards have a provision of two channels, thus a total of 4 EIDE devices can be connected internally.

They make use of a 40 or 80 wire ribbon cable transferring multiple bits of data simultaneously in parallel. These drives store data by the use of magnetism. The internal structure is one made of mechanical moving parts. They have been superseded by serial ATA.

An EIDE Hard Disk Drive

A hard disk drive (PATA type) | Source

Serial ATA

These hard drives have replaced the PATA drives in desktop and laptop computers. The main physical difference between the two is the interface, although their method of connecting to a computer is the same. Here are some advantages of SATA disk drives.

• SATA drives can transfer data faster than PATA types by using serial signalling technology.
• SATA cables are thinner and more flexible than PATA cables.
• They have a 7-pin data connection, with cable limit of 1 meter.
• Disks do not share bandwidth because there is only one disk drive allowed per SATA controller chip on the computer motherboard.
• They consume less power. They only require 250 mV as opposed to 5V for PATA.

Interface of SATA Drive

A SATA Hard Disk Drive Pin Out | Source

Small Computer System Interface

These are quite similar to IDE hard drives but they make use of the Small Computer System Interface to connect to the computer. SCSI drives can be connected internally or externally. Devices that are connected in a SCSI have to be terminated at the end. Here are some of their advantages.

• They are faster.
• They are very reliable.
• Good for 24/7 operations.
• Have a better scalability and flexibility in arrays.
• Well-adapted for storing and moving large amounts of data.

Solid State Drives

These are the latest in drive technology that we have in the computer industry. They are totally different from the other drives in that they do not consist of moving parts. They also do not store data using magnetism. Instead, they make use of flash memory technology. They make use of integrated circuits or semiconductor devices to store data permanently, at least until they are erased. Here are some of their advantages.

• Faster data access.
• Less susceptible to shock.
• Lower access times and latency.
• Durability.
• Less power usage.

Hard disk drive

A hard disk drive (HDD), hard disk, hard drive or fixed disk is an electromechanical data storage device that uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks (platters) coated with magnetic material. The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces.^[2] Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order and not only sequentially. HDDs are a type of non-volatile storage, retaining stored data even when powered off.^[3][4][5]

Introduced by IBM in 1956,^[6] HDDs became the dominant secondary storage device for general-purpose computers by the early 1960s. Continuously improved, HDDs have maintained this position into the modern era of servers and personal computers. More than 200 companies have produced HDDs historically, though after extensive industry consolidation most units are manufactured by Seagate, Toshiba, and Western Digital. HDDs dominate the volume of storage produced (exabytes per year) for servers. Though production is growing slowly, sales revenues and unit shipments are declining because solid-state drives (SSDs) have higher data-transfer rates, higher areal storage density, better reliability,^[7] and much lower latency and access times.^{[8][9][10][11]}

The revenues for SSDs, most of which use NAND, slightly exceed those for HDDs.^[12] Though SSDs have nearly 10 times higher cost per bit, they are replacing HDDs where speed, power consumption, small size, and durability are important.^[10][11]

The primary characteristics of an HDD are its capacity and performance. Capacity is specified in unit prefixes corresponding to powers of 1000: a 1-terabyte (TB) drive has a capacity of 1,000 gigabytes (GB; where 1 gigabyte = 1 billion bytes). Typically, some of an HDD's capacity is unavailable to the user because it is used by the file system and the computer operating system, and possibly inbuilt redundancy for error correction and recovery. Performance is specified by the time required to move the heads to a track or cylinder (average access time) plus the time it takes for the desired sector to move under the head (average latency, which is a function of the physical rotational speed in revolutions per minute), and finally the speed at which the data is transmitted (data rate).

The two most common form factors for modern HDDs are 3.5-inch, for desktop computers, and 2.5-inch, primarily for laptops. HDDs are connected to systems by standard interface cables such as PATA (Parallel ATA), SATA (Serial ATA), USB or SAS (Serial Attached SCSI) cables.

History

The first production IBM hard disk drive, the 350 disk storage shipped in 1957 as a component of the IBM 305 RAMAC system. It was approximately the size of two medium-sized refrigerators and stored five million six-bit characters (3.75 megabytes)^[13] on a stack of 50 disks.^[28]

In 1962 the IBM 350 was superseded by the IBM 1301 disk storage unit,^[29] which consisted of 50 platters, each about 1/8-inch thick and 24 inches in diameter.^[30] While the IBM 350 used only two read/write heads,^[28] the 1301 used an array of heads, one per platter, moving as a single unit. Cylinder-mode read/write operations were supported, and the heads flew about 250 micro-inches (about 6 µm) above the platter surface. Motion of the head array depended upon a binary adder system of hydraulic actuators which assured repeatable positioning. The 1301 cabinet was about the size of three home refrigerators placed side by side, storing the equivalent of about 21 million eight-bit bytes. Access time was about a quarter of a second.

Also in 1962, IBM introduced the model 1311 disk drive, which was about the size of a washing machine and stored two million characters on a removable disk pack. Users could buy additional packs and interchange them as needed, much like reels of magnetic tape. Later models of removable pack drives, from IBM and others, became the norm in most computer installations and reached capacities of 300 megabytes by the early 1980s. Non-removable HDDs were called "fixed disk" drives.

Some high-performance HDDs were manufactured with one head per track (e.g. IBM 2305 in 1970) so that no time was lost physically moving the heads to a track.^[31] Known as fixed-head or head-per-track disk drives they were very expensive and are no longer in production.^[32]

In 1973, IBM introduced a new type of HDD code-named "Winchester". Its primary distinguishing feature was that the disk heads were not withdrawn completely from the stack of disk platters when the drive was powered down. Instead, the heads were allowed to "land" on a special area of the disk surface upon spin-down, "taking off" again when the disk was later powered on. This greatly reduced the cost of the head actuator mechanism, but precluded removing just the disks from the drive as was done with the disk packs of the day. Instead, the first models of "Winchester technology" drives featured a removable disk module, which included both the disk pack and the head assembly, leaving the actuator motor in the drive upon removal. Later "Winchester" drives abandoned the removable media concept and returned to non-removable platters.

Like the first removable pack drive, the first "Winchester" drives used platters 14 inches (360 mm) in diameter. A few years later, designers were exploring the possibility that physically smaller platters might offer advantages. Drives with non-removable eight-inch platters appeared, and then drives that used a 5 ¹⁄₄ in (130 mm) form factor (a mounting width equivalent to that used by contemporary floppy disk drives). The latter were primarily intended for the then-fledgling personal computer (PC) market.

As the 1980s began, HDDs were a rare and very expensive additional feature in PCs, but by the late 1980s their cost had been reduced to the point where they were standard on all but the cheapest computers.

Most HDDs in the early 1980s were sold to PC end users as an external, add-on subsystem. The subsystem was not sold under the drive manufacturer's name but under the subsystem manufacturer's name such as Corvus Systems and Tallgrass Technologies, or under the PC system manufacturer's name such as the Apple ProFile. The IBM PC/XT in 1983 included an internal 10 MB HDD, and soon thereafter internal HDDs proliferated on personal computers.

External HDDs remained popular for much longer on the Apple Macintosh. Many Macintosh computers made between 1986 and 1998 featured a SCSI port on the back, making external expansion simple. Older compact Macintosh computers did not have user-accessible hard drive bays (indeed, the Macintosh 128K, Macintosh 512K, and Macintosh Plus did not feature a hard drive bay at all), so on those models external SCSI disks were the only reasonable option for expanding upon any internal storage.

The 2011 Thailand floods damaged the manufacturing plants and impacted hard disk drive cost adversely between 2011 and 2013.

Driven by ever increasing areal density, HDDs have continuously improved; a few highlights are listed in the table above. Market applications expanded through the 2000s, from the mainframe computers of the late 1950s to most mass storage applications including computers and consumer applications such as storage of entertainment content.

NAND performance is improving faster than HDDs, and applications for HDDs are eroding. Smaller form factors, 1.8-inches and below, were discontinued around 2010. The price of solid-state storage (NAND), represented by Moore's law, is improving faster than HDDs. NAND has a higher price elasticity of demand than HDDs, and this drives market growth.^[34]During the late 2000s and 2010s, the product life cycle of HDDs entered a mature phase, and slowing sales may indicate the onset of the declining phase.

Computer case

A computer case, also known as a computer chassis, tower, system unit, CPU (When referring to the desktop as a whole), or cabinet, is the enclosure that contains most of the components of a computer (usually excluding the display, keyboard and mouse).

Cases are usually constructed from steel (often SECC—steel, electrogalvanized, cold-rolled, coil) or aluminium. Plastic is sometimes used, and other materials such as glass, wood and even Lego bricks have appeared in home-built cases.

Sizes and terminology

Cases can come in many different sizes (known as form factors). The size and shape of a computer case is usually determined by the form factor of the motherboard, since it is the largest component of most computers. Consequently, personal computer form factors typically specify only the internal dimensions and layout of the case. Form factors for rack-mounted and blade servers may include precise external dimensions as well, since these cases must themselves fit in specific enclosures.

For example, a case designed for an ATX motherboard and power supply may take on several external forms such as a vertical tower (designed to sit on the floor, height > width), a flat desktop (height < width) or pizza box (height ≤ 5 cm (2 in) designed to sit on the desk under the computer's monitor). Full-size tower cases are typically larger in volume than desktop cases, with more room for drive bays, expansion slots, and custom or all-in-one (AIO) water cooling solutions. Desktop cases—and mini-tower cases under about 46 cm (18 in) high—are popular in business environments where space is at a premium.^[1]

Currently, the most popular form factor for desktop computers is ATX,^{[citation needed]} although microATX and small form factors have also become very popular for a variety of uses. In the high-end segment the unofficial and loosely defined XL-ATX specification appeared around 2009. It extends the length of the mainboard to accommodate four graphics cards with dual-slot coolers. Some XL-ATX mainboards increase the mainboard's width as well, to allow more space for the CPU, Memory PWM and, in some cases, a second CPU socket. While the market share of these exotic high-end mainboards is very low, almost all high-end cases and many mainstream cases support XL-ATX (10 expansion slots). As of 2018, no major motherboard manufacturer has made an XL-ATX board for several years. Companies like In Win Development, Shuttle Inc. and AOpen originally popularized small cases, for which FlexATX was the most common^{[dubious – discuss]} motherboard size. As of 2010 Mini ITX has widely replaced FlexATX as the most common small form factor mainboard standard. The latest mini ITX mainboards from Asus, Gigabyte, MSI, ASRock, Zotac and Foxconn offer the same feature set as full size mainboards. High-end mini ITX mainboards support standard desktop CPUs, use standard memory DIMM sockets and most feature a full size PCI-E 16× slot with support for the fastest graphics cards, although some instead use a PCI, or PCIe slot of less than 16 lanes. This allows customers to build a fully fledged high-end computer in a significantly smaller case. Apple Inc. has also produced the Mac Mini computer, which is similar in size to a standard CD-ROM drive, and many manufacturers offer mini-ITX cases of similar size for low wattage CPUs with integrated graphics.

Tower cases are often categorized as mini-tower, midi-tower, mid-tower or full-tower. The terms are subjective and inconsistently defined by different manufacturers.

Full tower cases are typically 56 cm (22 in) or more in height and intended to stand on the floor. They can have anywhere from six to ten externally accessible drive bays, although in recent years (as of 2018), this has shifted to offering better airflow in the front by moving the drive bays elsewhere in the case. The ratio of external to internal bays is shifting, however, as computing technology moves from floppy disks and CD-ROMs to large capacity hard drives, USB flash drives, and network-based solutions. The full tower case was developed to house file servers which would typically be tasked with serving data from expensive CD-ROM databases which held more data than the hard drives commonly available, but are moving now towards being showpiece display cases with custom water cooling, lighting, and tempered glass (replacing acrylic). Hence many full tower cases include locking doors and other physical security features to prevent theft of the discs. This is a high-end case intended for desktop systems and doesn't include security features.

Mid-tower cases are smaller, about 46 cm (18 in) high with two to four external bays.

A mini-tower case will typically have only one or two external bays.^[2]

Recently the marketing term midi-tower has come into use, seemingly referring to (based on anecdotal evidence) cases smaller than mid-tower but larger than mini-tower, typically with two to three external bays. Outside of the United States the term is often used interchangeably with mid-tower.

The computer case is sometimes erroneously referred to as the "CPU" or "hard drive".^[3][4]

Layout

Computer cases usually include sheet metal enclosures for a power supply unit and drive bays, as well as a rear panel that can accommodate peripheral connectors protruding from the motherboard and expansion slots. Most cases also have a power button or switch, a reset button, and LEDs to indicate power, hard drive activity, and network activity in some models. Some cases include built-in I/O ports (such as USB and headphone ports) on the front of the case. Such a case will also (normally) include the wires needed to connect these ports, switches and indicators to the motherboard.

Major component locations

• The motherboard is usually screwed to the case along its largest face, which could be the bottom or the side of the case depending on the form factor and orientation.
• Form factors such as ATX provide a back panel with cut-out holes to expose I/O ports provided by integrated peripherals, as well as expansion slots which may optionally expose additional ports provided by expansion cards. Many larger ATX cases can also be used with motherboards of other form factors.
• The power supply unit mounting point differs from case to case, but the most commonly used locations (both at the rear of the case) and their benefits/disadvantages are:
  • The top of the case, usually allowing the PSU's built-in fan to act as an auxiliary exhaust fan, but causes the PSU to be fed air heated by the internal components of the case, thus causing PSU efficiency and lifespan degradation.
  • The bottom of the case, with a (often filtered) vent in the bottom of the case allowing the PSU to draw cool air from the outside.
• Regardless of the mounting position, the PSU will usually be attached to the case with four screws to support its weight.
• Most cases include drive bays on the front of the case; a typical ATX case includes 5.25", 3.5" and 2.5" bays. In modern computers, the 5.25" bays are used for optical drives, the 3.5" bays are used for hard drives and card readers, and the 2.5" bays are used for solid-state drives.
• Buttons and LEDs are typically located on the front of the case; some cases include additional I/O ports, temperature and processor speed monitors in the same area.
• Vents are often found on the front, back, top, left side panel, and sometimes on the right side panel of the case. Regardless of their placement, their purpose is either to let cool air into the case, or to let hot air out. Larger vents usually allow cooling fans to be mounted via surrounding threaded screw holes. Newer cases include mountings for larger 120mm or 140mm cooling fans for quieter operation than the 80mm fans formerly common.

Internal access

Accessing the interior components of a modern tower case is done by removing the side panels. Looking front-to-back, accessing the motherboard, PSU, drive bays and most case fan installation points is done by removing the left side panel. Removing the right side panel is done less often to access the space behind the motherboard mounting plate. This space is devoted to cable management, as cables routed in front of the motherboard will cause disruptions in the flow of air within the case.

Alternatively, the case may have a single large U-shaped cover that saddles the chassis.

To prevent the buildup of performance-degrading dust within the case, many models feature dust filters in front of the air intake fans. While the exact method of accessing the front filters depends on the case model, it usually requires the removal of the entire front panel. Removal of the front panel itself may or may not require the removal of one or both of the side panel. If there is any doubt, consult the user's manual if possible.

Traditionally, most computer cases required computer case screws to hold components and panels in place (i.e. motherboard, PSU, drives, and expansion cards). From the 2000s there is a trend towards tool-less cases, in which components are held together with snap-in plastic rails, thumbscrews, and other methods that do not require tools; this facilitates quick assembly and modification of computer hardware, and is also cheaper to manufacture.

Appearance

Further information: Case modding

Through the 1990s, most computer cases had simple rectangular shapes, and were often painted beige or white with little attention given to visual design. Beige box designs are still found on a large number of budget computers assembled from generic components. This class of machines is still known as white box computers. More modern computer cases include a much wider range of variation in shape, form factor and materials, such as brushed aluminium and/or tempered glass which are offered with more expensive cases.

Case modding is the artistic styling of computer cases, often to draw attention to the use of advanced or unusual components. Since the early 2000s, some cases have included clear side panels or acrylic windows so that users can look inside while it is operating. Modded cases may also include internal lighting, custom paint, or liquid cooling systems. Some hobbyists build custom cases from raw materials like aluminum, steel, styrofoam, acrylic, or wood.

Case manufacturers

See also: List of computer hardware manufacturers § Computer cases

Prominent after-market case manufacturers include Antec, BitFenix, Cooler Master, Corsair, Fractal Design, In Win Development, Lian Li, NZXT Corp., Phanteks, Rosewill, and Thermaltake, (DIY PC)

Intrusion detection

Some computer cases include a biased switch (push-button) which connects to the motherboard. When the case is opened, the switch position changes and the system records this change. The system's firmware or BIOS may be configured to report this event the next time it is powered on.

This physical intrusion detection system may help computer owners detect tampering with their computer. However, most such systems are quite simple in construction; a knowledgeable intruder can open the case or modify its contents without triggering the switch.

In the past, many tower cases intended to house file servers featured a locking door covering the external drive bays. This was a security feature intended to prevent the theft of the CD-ROM discs the drives would be holding. At the time, CD-ROM capacity was larger than the hard disks available, and many business-critical databases were distributed on this media. These databases were often very expensive or held proprietary data, and hence would be likely targets for casual theft.

What IS PC SMPS ?

Short for Switched-Mode Power Supply, SMPSis a power supply that uses a switching regulator to control and stabilize the output voltage by switching the load current on and off. These power supplies offer a greater power conversion and reduce the overall power loss.

Interior view of an ATX SMPS: below
A: input EMI filtering and bridge rectifier;
B: input filter capacitors;
Between B and C: primary side heat sink;
C: transformer;
Between C and D: secondary side heat sink;
D: output filter coil;
E: output filter capacitors.  
The coil and large yellow capacitor below E are additional input filtering components that are mounted directly on the power input connector and are not part of the main circuit board.

An adjustable switched-mode power supply for laboratory use

A switched-mode power supply (switching-mode power supply, switch-mode power supply, switched power supply, SMPS, or switcher) is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. Like other power supplies, an SMPS transfers power from a DC or AC source (often mains power) to DC loads, such as a personal computer, while converting voltage and current characteristics. Unlike a linear power supply, the pass transistor of a switching-mode supply continually switches between low-dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions, which minimizes wasted energy. Ideally, a switched-mode power supply dissipates no power. Voltage regulation is achieved by varying the ratio of on-to-off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. This higher power conversion efficiency is an important advantage of a switched-mode power supply. Switched-mode power supplies may also be substantially smaller and lighter than a linear supply due to the smaller transformer size and weight.

Switching regulators are used as replacements for linear regulators when higher efficiency, smaller size or lighter weight are required. They are, however, more complicated; their switching currents can cause electrical noise problems if not carefully suppressed, and simple designs may have a poor power factor.

What IS Motherboard?

A motherboard is the main printed circuit board (PCB) in a computer. The motherboard is a computer’s central communications backbone connectivity point, through which all components and external peripherals connect.

The large PCB of a motherboard may include 6-14 layers of fiberglass, copper connecting traces and copper planes for power and signal isolation. Additional components can be added to a motherboard through its expansion slots. These may include processor sockets, DIMM, HTX, PCI, PCIe and M.2 slots as well as power supply connections. Typically motherboards offer additional connectivity through a Southbridge chip such as PCI, SATA, Thunderbolt, USB and more. CPU to RAM and PCIe are generally connected through point-to-point interconnects such as hypertransport (HT), quick path interconnect (QPI) or Ultrapath interconnect (UPI). Often, choosing a motherboard determines many of the features a desktop will have.

The most common motherboard design in desktop computers today is ATX, an Intel improvement on the AT design by IBM. Other form factors include extended ATX mini-ATX, microATX, BTX, microBTX mini ITX, micro ITX and nano ITX.

The integration of components has eliminated the Northbridge chips that managed memory from motherboards. With the advent of memory controllers built into CPU, integrated video too has moved from motherboard to CPU. On AMD’s new Ryzen, even the Southbridge is optional due to the SOC (system on a chip) nature of the CPU. This integration into the CPU reduces the cost for motherboard manufacturers who wish to offer base systems for workstations and entry level computers while also enabling highly customized implementations that support a range of processors to allow for platform upgradabillity.

This was last updated in December 2016

Continue Reading About motherboard

• Types of motherboards

• See questions and answers related to motherboards

• Tom's Hardware motherboard section

• Bypassing BIOS passwords

• A review of the best motherboards for diferent platforms and purposes at Techspot

List of Input Devices, Output Devices and Both Input Output devices related to computer.

Here I am going to share you about list of  basic Input Devices, Output devices and  Both input–output devices  related to computer.

 Input Devices:

a)      Graphics Tablets

b)      Cameras

c)      Video Capture Hardware

d)     Trackballs

e)      Barcode reader

f)       Digital camera

g)      Gamepad

h)      Joystick

i)        Keyboard

j)        Microphone

k)      MIDI keyboard

l)        Mouse (pointing device)

m)    Scanner

n)      Webcam

o)      Touchpads

p)      Pen Input

q)      Microphone

r)       Electronic Whiteboard

s) OMR

t) OCR

u) Punch card reader

v)MICR (Magnetic Ink character reader)

w) Magnetic Tape Drive

 OUTPUT  DEVICES:

1. Monitor (LED, LCD, CRT etc)
2. Printers (all types)
3. Plotters
4. Projector
5. LCD Projection Panels
6. Computer Output Microfilm (COM)
7. Speaker(s)
8. Head Phone
9. Visual Display Unit
10. Film Recorder
11. Microfiche

Both Input–OutPut Devices:

1. Modems
2. Network cards
3. Touch Screen

      4. Headsets (Headset consists of Speakers and Microphone. 

           Speaker act Output Device and     Microphone act as Input 

            device)

     5. Facsimile (FAX)  (It has scanner to scan the document and also 

           have printer to Print the  document)

     6.Audio Cards / Sound Card