BUS
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 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
16bit ISA Slot
PCI
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 Slot
AGP
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 Slot
Expansion 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 is
hot swappable
USB can
daisy chain up to 127 devices
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_A Connector 
USB_B Connector
AMR
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
Slots
| Type
of Bus |
Bits
Wide |
Clock
Speed |
Transfer
Speed |
| PCI-X (v1) |
64bit |
66MHz * 8 = |
528MB/s |
| PCI-X (v1) |
64bit |
100MHz * 8 = |
800MB/s |
| PCI-X (v1) |
64bit |
133MHz * 8 = |
1066MB/s |
PCI Express A high speed serial I/O interconnect standard being used for
high speed connection it will eventually replace the PCI standards
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 |
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
Special
Thanks to Belkin, nVidia, Linksys, ATI and Intel
Bus
