Bus Technical Specifications

8 data bits, 20 address bits
4.77 MHz

Note:
It's one of the first PC Buses.
Many XT cards also operate under ISA Bus.
Is no longer in use.

ISA (Industry Standard Architecture) bus:

8 / 16 data bits, 24 address bits
8.33MHz, asynchronous
5.55M/s burst
bus master support
edge triggered TTL interrupts (IRQs) - no sharing

Note:
Fair performance and ideal for non demanding cards.
It's a standard in every PC.
Low cost.

MCA (Micro Channel Architecture) bus:

16 / 32 data bit, 32 address bits
80M/s burst, synchronous
full bus master capability
auto configurable

Note:
Developed by IBM and used only in their computers.
Not compatible with all other systems.
High performance.
High cost.

EISA (Enhanced Industry Standard Architecture) bus:

32 data bits, 32 address bits
8-8.33MHz, synchronous
32M/s burst (sustained)
full bus master capability
auto configurable
sharable IRQs, DMA channels

Note:
Good performance and ideal for demanding cards.
Compatible with ISA.
High cost.

VL (VESA Local) Bus:

32 data bits, 32 address bits
25-40MHz, asynchronous
130M/s burst (sustained is closer to 32M/s)
bus master capability
2 or 3 slots limited

Note:
High performance and ideal for video cards.
Coexists and is backwards compatible with EISA/ISA.
Medium cost.

PCI (Peripheral Component Interconnect) bus:

32 data bits (64 bit option), 32 address bits (64 bit option)
up to 33MHz, synchronous
132M/s burst (sustained) (264M/s with 64 bit option)
full bus master capability
auto configurable
3 or 4 slots limited