1. System Bus

2. XT Mother-boards “extended technology.”
Configured manually using jumpers, switches or both.
Designed around the Intel 8088 processor.
XT Mother-boards “extended technology.”
Has an eight-bit ISA bus
Limited to 1MB of memory

3. System Bus
The heart of any motherboard are the various buses that carry signals between the components.
The PC has a hierarchy of different buses ordered by their speed.
AGP System bus
Processor System bus
Each device in the system is connected to a bus
ISA System bus
PCI System bus

4. Processor System Bus
Processor System Bus is also called the front side bus
Primarily used by the processor to pass information to and from cache, main memory and the North bridge
It is the highest speed bus

5. AGP System Bus AGP System Bus is a high speed 32 bit bus
Primarily used for video and is connected to the North bridge
Only one AGP bus per system

6. PCI System Bus PCI System Bus is normally a 32 bit bus
Primarily used by all newer 486 and higher processor systems

7. ISA System Bus ISA System Bus is a very slow speed 8 Mhz, 16 bit bus
The Super I/O chip usually was connected to the ISA Bus
ISA Bus is generated by the South Bridge, which acts as the controller and interface between the ISA Bus and the faster PCI Bus
Most new motherboards no longer support ISA

8. Expansion I/O Buses Standardized Connectors on the motherboard
This is where peripheral devices are attached
ISA
AGP
PCI
MCA
VESA
PCMCIA/PC Card
EISA
Allows for exceptional flexibility
Processor speed bottleneck

9. ISA (Industry Standard Architecture 8/16-bit )
8 bit ISA Card
16 bit ISA Card
Originally ran at 4.77 MHz with 8 bit cards
Supports 16 bit slots while staying backward compatible with 8 bit cards
With 16 bit cards ran at 6 MHz, then 8 MHz, then finally standardized at 8.33 MHz
Black in Color

10. MCA (Microchannel Architecture 16/32-bit)
Introduced by IBM
Not compatible with ISA cards
May be 16 bit or 32 bit depending on the card
32 bit MCA Card
Brown in Color
Supports bus mastering. This can control the bus and act as if it were the entire systems

11. EISA (Extended Industry Standard Architecture 32-bit)
Created by Compaq, so they would not have to pay royalties to IBM
32 bit throughput with an automated setup
Supported bus mastering and would work with 16 bit ISA cards
32 bit EISA Card
Brown in Color/ Two levels

12. VESA (Video Electronics Standards Association 32-bit Local Bus)
Limited to 3 cards
Referred to as VL bus (VESA local bus)
Direct access to Processor Bus, therefore direct access to system memory for higher speeds than others
Faded into history because of speed issues, but was resurrected as AGP
32 bit VESA Card
Completely different physical makeup to prevent plugging in slower cards
Brown in Color

13. PCI (Peripheral Component Interconnect 32/64 bit Local)
Developed in 1992 to solve the problem of fast CPU’s
Transfers data at 33 MHZ at full data width
Operates at same time as the CPU without replacing it
32 Bit PCI Card
White in Color

14. PC Card (PCMCIA)
Introduced in 1990 to give laptop and notebook computers expansion capabilities
4 standard types
Type 1 : 3.3mm
Type 2 : 5mm
Type 3 : 10.5mm
Type 4 : 10.5mm & up
Included in the PnP (plug and play) specification
Introduced concept of combining the device and its I/O card on the card

15. Accelerated Graphic Port
One of the main reasons Intel designed the AGP was to allow the video card to have a high speed connection directly to the system ram
The AGP was created in 1996 as a bus specifically designed for high performance graphics and video support
AGP is a high speed connection and runs at a base frequency of 66 MHZ which is double that of a standard PCI
AGP is based on PCI, but it contains additions and enhancements and is physically, electronically, and logically independent of the PCI