External Bus

The external bus is also referred to as the expansion bus. There are six major types of external bus’s found on the common motherboard. Only a few of these are actually found on the home PC such as ISA, PCI, AGP, USB and IDE. These slots are easily recognized on the board. They are usually covered with pins on the inside channel. Some of these pins are made of tin or gold. The pins themselves actually mount into the internal bus. Some pins provide power to you component or connect to the data, address bus’s. Here is a description of some common buses

ISA (Industry Standard Architecture), This bus is the low speed work horse of the system. You will commonly find a Sound Card hooked up this type BUS.

PCI (Peripheral Component Interconnect), Supports 32-64 bit bus and is the reigning standard of external buses. The PCI is fast and is slowly making the ISA fade away. Go with a PCI BusCard when possible.

AGP (Accelerated Graphics Port), This Bus provides from 2 to 4 times the speed of the PCI and is used for video expansion only. If you have this slot on your motherboard make sure and use it for you video card. This is great way to go and takes a lot of stress off the CPU, thus gaining in performance all the way around.

USB (Universal Serial Bus), This is something that is fairly new and allows you to hook up to 127 devices. This is probably going to wipe out PS/2 ports and more. The USB is allows you to hot swap devices or plug and unplug devices while system is running. This is a great feature and is incorporated on most new motherboards.

IDE (Intelligent Drive Electronics), This bus is used mostly for disk drives and connects up to two devices on one connection. More than likely you’re hard drive and CD-ROM are connected through this type bus.

There are a few more bus types that are not very common and some are not even in uses in modern computers. The buses above are the most common and found in modern motherboards.

-So what are the slots mad up off? We already know that there are little pins made out of gold and tin, but what else? Check out the Slot's Makeup

Overview of motherbord

A motherboard, like a backplane, provides the electrical connections by which the other components of the system communicate, but unlike a backplane, it also connects the central processing unit and hosts other subsystems and devices.




A typical desktop computer has its microprocessor, main memory, and other essential components connected to the motherboard. Other components such as external storage, controllers for video display and sound, and peripheral devices may be attached to the motherboard as plug-in cards or via cables, although in modern computers it is increasingly common to integrate some of these peripherals into the motherboard itself.



An important component of a motherboard is the microprocessor's supporting chipset, which provides the supporting interfaces between the CPU and the various buses and external components. This chipset determines, to an extent, the features and capabilities of the motherboard.



Modern motherboards include, at a minimum:



sockets (or slots) in which one or more microprocessors may be installed[3]

slots into which the system's main memory is to be installed (typically in the form of DIMM modules containing DRAM chips)

a chipset which forms an interface between the CPU's front-side bus, main memory, and peripheral buses

non-volatile memory chips (usually Flash ROM in modern motherboards) containing the system's firmware or BIOS

a clock generator which produces the system clock signal to synchronize the various components

slots for expansion cards (these interface to the system via the buses supported by the chipset)

power connectors, which receive electrical power from the computer power supply and distribute it to the CPU, chipset, main memory, and expansion cards.[4]



The Octek Jaguar V motherboard from 1993.[5] This board has 6 ISA slots but few onboard peripherals, as evidenced by the lack of external connectors.Additionally, nearly all motherboards include logic and connectors to support commonly used input devices, such as PS/2 connectors for a mouse and keyboard. Early personal computers such as the Apple II or IBM PC included only this minimal peripheral support on the motherboard. Occasionally video interface hardware was also integrated into the motherboard; for example, on the Apple II and rarely on IBM-compatible computers such as the IBM PC Jr. Additional peripherals such as disk controllers and serial ports were provided as expansion cards.



Given the high thermal design power of high-speed computer CPUs and components, modern motherboards nearly always include heat sinks and mounting points for fans to dissipate excess heat.