A bus is a set of signal pathways that allow information to travel between components inside or outside of a computer.
Types of Bus
External bus or Expansion bus allows the CPU to talk to the other devices in the computer and vice versa. It is called that because it's external to the CPU.
Address bus allows the CPU to talk to a device. It will select the particular memory address that the device is using and use the address bus to write to that particular address.
Data bus allows the device to send information back to the CPU
Types of Bus
External bus or Expansion bus allows the CPU to talk to the other devices in the computer and vice versa. It is called that because it's external to the CPU.
Address bus allows the CPU to talk to a device. It will select the particular memory address that the device is using and use the address bus to write to that particular address.
Data bus allows the device to send information back to the CPU
Types of Expansion Buses
ISA
Introduced by IBM, ISA or Industry Standard Architecture was originally an 8-bit bus and later expanded to a 16-bit bus in 1984. When this bus was originally released it was a proprietary bus, which allowed only IBM to create peripherals and the actual interface. Later however in the early 1980's the bus was being created by other clone manufacturers.
This is still in use because it's cheap and for backwards compatibility
16bit ISA Card
ISA
Introduced by IBM, ISA or Industry Standard Architecture was originally an 8-bit bus and later expanded to a 16-bit bus in 1984. When this bus was originally released it was a proprietary bus, which allowed only IBM to create peripherals and the actual interface. Later however in the early 1980's the bus was being created by other clone manufacturers.
This is still in use because it's cheap and for backwards compatibility
16bit ISA Card
16bit ISA SlotPCI
Introduced by Intel in 1992, PCI is short for Peripheral Component Interconnect and is a 32-bit or 64-bit expansion bus.
The PCI bus is the most popular expansion bus use in today's computers
PCI Card 
PCI SlotAGP
Introduced by Intel in 1997, AGP or Advanced Graphic Port is a 32-bit bus or 64-bit bus designed for the high demands of 3-D graphics. AGP has a direct line to the computers memory which allows 3-D elements to be stored in the system memory instead of the video memory.
AGP is one of the fastest expansion bus in use but its only for video or graphics environment.
AGP Card
AGP SlotExpansion Bus Chart:
| Type of Bus | Bits Wide | Clock Speed | Transfer Speed |
| ISA | 8 bit | 4.77 MHz | 2.38MB/s |
| ISA | 16 bit | 8.33 MHz | 8MB/s |
| PCI (Client) | 32 bit | 33MHz | 133MB/s |
| PCI (Server) | 64 bit | 66MHz | 266MB/s |
| AGP 1x | 32 bit | 66MHz | 266MB/s |
| AGP 2x | 32 bit | 66MHz | 533MB/s |
| AGP 4x | 32 bit | 66MHz | 1,066MB/s |
| AGP 8x | 32 bit | 66MHz | 2,133MB/s |
| AGP 8x (high-end) | 64 bit | 66MHz | 4,266MB/s |
Bus Mastering-Ability of bus device to bypass the CPU can be set at the CMOS setup
Other Buses
USB
USB or Universal Serial Bus is an external bus that most popular form of bus use today
USB or Universal Serial Bus is an external bus that most popular form of bus use today
USB is hot swappable
USB can daisy chain up to 127 devices
USB Speeds
USB Speeds
USB 1.0 supports 1.5Mbps
USB 1.1 supports 12Mbps
USB 2.0 supports up to 480Mbps
USB 3.0 supports up to 4.8Gbps
USB 1.1 supports 12Mbps
USB 2.0 supports up to 480Mbps
USB 3.0 supports up to 4.8Gbps
USB_A Connector 
USB_B ConnectorAMR
Released September 8, 1998, AMR is short for Audio/Modem Riser. AMR allows an OEM to create one card that has the functionality of either Modem or Audio or both Audio and Modem on one card. This new specification allows for the motherboard to be manufactured at a lower cost and free up industry standard expansion slots in the system for other additional plug-in peripherals.
Released September 8, 1998, AMR is short for Audio/Modem Riser. AMR allows an OEM to create one card that has the functionality of either Modem or Audio or both Audio and Modem on one card. This new specification allows for the motherboard to be manufactured at a lower cost and free up industry standard expansion slots in the system for other additional plug-in peripherals.
AMR Slot CNR
Introduced by Intel February 7, 2000, CNR is short for Communication and Network Riser and is a specification that supports audio,modem USB and Local Area Networking interfaces of core logic chipsets.
CNR Slot PCI-X
PCI-X is a high performance bus that is designed to meet the increased I/O demands of technologies such as Fibre Channel, Gigabit Ethernet and Ultra3 SCSI.
PCI-X card
PCI-X is a high performance bus that is designed to meet the increased I/O demands of technologies such as Fibre Channel, Gigabit Ethernet and Ultra3 SCSI.
PCI-X card 
PCI-X Slots| Type of Bus | Bits Wide | Clock Speed | Transfer Speed |
| PCI-X (v1) | 64bit | 66MHz * 8 = | 533MB/s |
| PCI-X (v1) | 64bit | 100MHz * 8 = | 800MB/s |
| PCI-X (v1) | 64bit | 133MHz * 8 = | 1066MB/s |
PCI-e Card PCI-Express
| Lane Widths | Peak unidirectional bandwidth | Peak full duplex bandwidth |
| x1 | 250MB/s | 500MB/s |
| x2 | 500MB/s | 1GB/s |
| x4 | 1GB/s | 2GB/s |
| x8 | 2GB/s | 4GB/s |
| x16 | 4GB/s | 8GB/s |
| x32 (new) | 8GB/s | 16GB/s |
Laptop Buses
PCMCIA or PC Card
Personal Computer memory card international association is a type of bus use for laptops. There are different types of cards and you primarily slide in the card in a PC card slot of a laptop.
Type II PCMCIA Card| PC Card Types | Measurement | Usage |
| Type I | 3.3mm | Flash Memory |
| Type II | 5.0mm | USB/NIC/Wireless |
| Type III | 10.5mm | Hard Drive |
PCMCIA cards supports 16 or 32 bit bus width
Express Card is the newest form of card you insert in newer laptops
