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Motherboard Buses
eMachines Training Department

 

Introduction

A bus is a transport system that allows different parts of the computer to communicate. A bus is a physical component of the motherboard. All of the interconnected lines and gold tracing that you see on a motherboard make up the bus.

There are different speeds that a motherboard bus can run. Faster is better because you get to your destination sooner. Assume for the moment you take the bus to work. The bus stop you wait at only shows up every 30 minutes. If you come right in the middle of that 30 minute time or just 2 minutes after the bus has already left, you are going to have to wait awhile and it is going to take you longer to get to your destination. If the bus were to travel every 2 minutes that would be monumentally faster than if it only came every 30 minutes. That is why different motherboards and newer ones especially have a higher bus speed.

FSB (Front Side Bus)

The front side bus is just a part of the bus that deals with main system memory. It is meant to transfer a lot of information as it has to deal constantly with system memory for all applications running. Common speeds for this are 133, 233, 266, 400, 466 MHz. For a system that has DDR memory the front side bus is normally quoted as DDR 3700, 3200, 2700, 2100, etc.

FDC (Floppy Disk Controller)

The standard connection for a floppy drive is a 34-pin connection. The cable looks very much like an IDE cable, except slightly smaller, and it has a twist in the cable. The driver for the FDC can be found under floppy disk controllers. Unlike an IDE cable, not all floppy disk drives have the cable plugged in a specific way. Plugging the cable in backwards simply causes the floppy disk drive not to work and the light to stay on while the system is booting.

IDE (Integrated Drive Electronics)

IDE is the primary connection for both hard drives and most optical drives.




The cable connection is a long gray cable with 40 pins. It is possible to have 2 IDE devices per IDE controller. All eMachines motherboards have 2 IDE controllers so have a maximum of 4 IDE devices. There is a primary IDE controller and a secondary controller.



40-pin vs. 80-pin

There are two different types of cables that can connect to an IDE port: a 40-pin connection and an 80-pin connection. The connect color for a normal 40-pin is black while an 80-pin is blue. The 80-pin has more wires which act as grounding allowing more information to be sent with less chance of disruption by electromagnetic interference from other close wires. A 40-pin cable can transfer of speeds of ATA 33 and below. For ATA 66, 100, or 133, you will need an 80-pin connection.

Jumper Configuration



An IDE controller needs to distinguish between two different devices connected to the same IDE controller. Because of this need, there are 3 options which are configured by a jumper on the actual IDE drive. They are Master, Slave, and Cable Select. By default, all eMachines IDE devices are configured as cable select.

• If there are two devices one must be set to master and one to slave OR both must be set to cable select.
• If there is only one device, it must be set to cable select or master.

If the drives are set to cable select, whichever port the IDE device is plugged into determines whether it is master or slave. The end of the cable is always master whereas the middle is always slave.


AGP (Accelerated Graphics Port)

An AGP port is used for video cards. Not all motherboards have an AGP port. AGP can even be used to refer to onboard cards built into the motherboard and in that circumstance AGP is just used as a speed quantifier rather than the port itself. Having an AGP onboard video card means that you have a graphics card built into the motherboard that cannot be removed however it does run at a fast speed.

Port speed for an AGP port is referred to as throughput. As technology evolves this number will eventually get higher. Looking up the card in the motherboard will tell you how fast the port runs. (eg. AGP 8x will also support a 4x, 2x, or 1x AGP video card.)




PCI (Peripheral Component Interconnect)

PCI is the standard slot used for most devices. Many eMachines have between 3-5 PCI slots that can have anything added to them. (eg. modem, sound card, video card, network card, etc.)