In ,computer architechture a bus is a subsystem that transfers data between computer components inside a computer or between computers. Unlike a point-to-point connection, a bus can logically connect several peripherals over the same set of wires. Each bus defines its set of connectors to physically plug devices, cards or cables together.
Early computer buses were literally parallel electrical buses with multiple connections, but the term is now used for any physical arrangement that provides the same logical functionality as a parallel electrical bus. Modern computer buses can use both parallel and bit-serial connections, and can be wired in either a multidrop (electrical parallel) or daisy chain topology, or connected by switched hubs, as in the case of USB.
A control bus is (part of) a computer bus, used by CPUs for communicating with other devices within the computer. While the address bus carries the information on which device the CPU is communicating with and the data buss carries the actual data being processed, the control bus carries commands from the CPU and returns status signals from the devices, for example if the data is being read or written to the device the appropriate line (read or write) will be active (logic zero).
An address bus is a computer bus, controlled by CPUs or DMA-capable peripherals for specifying the physical addresses of computer memory elements that the requesting unit wants to access (read or write).
The width of an address bus, along with the size of addressable memory elements, generally determines how much memory can be directly accessed. For example, a 16-bit wide address bus (commonly used in the 8-bit processors of the 1970s and early 1980s) reaches across 216 (65,536) memory locations , whereas a 32-bit address bus common in PC processors as of 2004 update can address 232 4,294,967,296 locations. Some microprocessors, such as the Digital Compaq Hewlett-Packard Alpha 21264 and Alpha 21364 have an address bus that is narrower than the amount of memory they can address. The address bus is clocked faster than the system or memory bus, enabling it to transfer an address in the same amount of time as an address bus of the same width as the address.
In most microcomputers such addressable "locations" are 8-bit bytes, conceptually at least. In such case the above examples translate to 64 kilobytes (KB) and 4 gigabytes (GB) respectively. However, it should be noted that accessing an individual byte frequently requires reading or writing the full bus width a word at once. In these instances the least significant bits of the address bus may not even be implemented - it is instead the responsibility of the controlling device to isolate the individual byte required from the complete word transmitted. This is the case, for instance, with the VESA Local Bus which lacks the two least significant bits, limiting this bus to aligned 32 bit transfers.
Historically, there were also some examples of computers which were only able to address larger words, such as 36 or 48 bits long.
Wednesday, December 10, 2008
CPU rear/back
1.Power Supply unit
2.Ps/2 ports
3.USB port
4.Parallel port
5.Serial port
6.AGP port
7.Lan port
8.Expansion slot
Basic parts of a motherboard
A.CPU slot G.PS/2 port
B.RAM socket I.IDE for FDD
C.IDE for the primary&secondary Devices J.Power terminal for mainboard
D.AGP slot K.CMOS battery
E.PCI slot L.Auxiliary ports
F.Serial & parallel port M.USB port
G.PS/2 port
I.IDE slot for FDD
J.Power terminal for mainboard
K.CMOS battery
L.Auxiliary ports
M.USB port
history of computer hardware
Computer Hardware - A History
Computer hardware has transformed in the last few decades as computers evolved from bulky, beige monsters to sleek and sexy machines. Computer Hardware – a History The dictionary defines ‘computer’ as any programmable electronic device that can store, retrieve, and process data. Computer Hardware evolved as data storage, calculation and data processing became important elements in work and life. In fact, the earliest computer Hardware is thought to be record keeping aids such as clay shapes that represented items in the real world – the early mechanics of merchants and accountants of the past. From the abacus and the slide rule came analogue and later, the electronic computer Hardware known today. A timeline of the history of computer Hardware: 1632 the first mechanical calculator was built by Wilhelm Schickard. It used cogs and gears and became the predecessor for computer Hardware. 1801 punched card technology began and by 1890 sorting machines were handling data, the first computer Hardware and installations used punched cards until the 1970s. 1820, Charles Xavier Thomas created the first mass-produced calculator. 1835, Charles Babbage described his analytical engine, which was the layout of a general-purpose programmable computer. 1909, Percy Ludgate designed a programmable mechanical computer. 1914, a central component in computer Hardware – the binary numeral system- was described by Leibniz. 1930s, desktop mechanical calculators, cash registers and accounting machines were introduced. By the 1960s, calculators advanced with integrated cuircuits and microprocessors. Digital computer Hardware replaced analogue computers. Digital computer Hardware The era of the computer as we know it today began with developments during the Second World War as researchers and scientists were spurred on by the military. 1960s and beyond ‘Third generation’ computer Hardware took off post 1960 thanks to the invention of the integrated circuit or microchip. This led to the microprocessor which in turn led to the microcomputer – computer Hardware that could be owned by individuals and small businesses. Steve Wozniak co-founded Apple Computer and is credited with developing the first mass market computer, although the KIM-1 and Altair 8800 came first. Evolution in computer Hardware After the 1970s the personal computer and evolution in computer Hardware exploded across the western world. Microsoft, Apple and many other PC companies fuelled the market and today, these companies are still striving to reduce the size and price of computer Hardware while improving its capacity.
Computer hardware has transformed in the last few decades as computers evolved from bulky, beige monsters to sleek and sexy machines. Computer Hardware – a History The dictionary defines ‘computer’ as any programmable electronic device that can store, retrieve, and process data. Computer Hardware evolved as data storage, calculation and data processing became important elements in work and life. In fact, the earliest computer Hardware is thought to be record keeping aids such as clay shapes that represented items in the real world – the early mechanics of merchants and accountants of the past. From the abacus and the slide rule came analogue and later, the electronic computer Hardware known today. A timeline of the history of computer Hardware: 1632 the first mechanical calculator was built by Wilhelm Schickard. It used cogs and gears and became the predecessor for computer Hardware. 1801 punched card technology began and by 1890 sorting machines were handling data, the first computer Hardware and installations used punched cards until the 1970s. 1820, Charles Xavier Thomas created the first mass-produced calculator. 1835, Charles Babbage described his analytical engine, which was the layout of a general-purpose programmable computer. 1909, Percy Ludgate designed a programmable mechanical computer. 1914, a central component in computer Hardware – the binary numeral system- was described by Leibniz. 1930s, desktop mechanical calculators, cash registers and accounting machines were introduced. By the 1960s, calculators advanced with integrated cuircuits and microprocessors. Digital computer Hardware replaced analogue computers. Digital computer Hardware The era of the computer as we know it today began with developments during the Second World War as researchers and scientists were spurred on by the military. 1960s and beyond ‘Third generation’ computer Hardware took off post 1960 thanks to the invention of the integrated circuit or microchip. This led to the microprocessor which in turn led to the microcomputer – computer Hardware that could be owned by individuals and small businesses. Steve Wozniak co-founded Apple Computer and is credited with developing the first mass market computer, although the KIM-1 and Altair 8800 came first. Evolution in computer Hardware After the 1970s the personal computer and evolution in computer Hardware exploded across the western world. Microsoft, Apple and many other PC companies fuelled the market and today, these companies are still striving to reduce the size and price of computer Hardware while improving its capacity.
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