Difference Between 8 bit ISA, 16 bit ISA and EISA

Characteristics	ISA( 8 Bit)	ISA (16 Bit)	EISA
Acronym for	Industry Standard Architecture	Industry Standard Architecture	Enhanced Industry Standard Architecture
Introduced In	1981	1984	1988
Introducer	IBM	IBM	Group of Nine Computer manufacturing Companies Led by Compaq(AST Research, Compaq Computer, Epson, Hewlett-Packard, NEC, Olivetti, Tandy, WYSE, Zenith Data Systems)
Data Bus	8 Bits	16 Bits	32 Bits
Address Bus	De-multiplexed 20 Bit address Bus	24 Bit Address Bus	32 Bit Address Lines
Memory Addressability	1.048576 MB	Up to 16 MB	Up to 4GB
DMA Channels Supported	DRQ1, DRQ2 and DRQ3	DRQ1, DRQ2 ,DRQ3, DRQ0, DRQ5, DRQ6, DRQ7	DRQ1, DRQ2, DRQ3, DRQ0, DRQ5, DRQ6, DRQ7
Interrupts	IRQ2, IRQ3, IRQ4, IRQ5, IRQ6, IRQ7.	IRQ2, IRQ3, IRQ4, IRQ5, IRQ6, IRQ7, IRQ10, IRQ11, IRQ12, IRQ14, IRQ15. IRQ13 is not available to expansion bus and has been assigned to math Co processor. IRQ9 is wired to IRQ2 and that’s why there is no such interrupt line in ISA bus.IRQ8 has been assigned to RTC( Real Time Clock) of system and is not available in expansion bus	IRQ0 (Timer 0), IRQ1 (Keyboard), SRQ2 (cascading according to the second PIC in the AT), IRQ3 (COM 2), IRQ4 (COM 1), IRQ5 (LPT2), IRQ6 (Floppy Controller), IRQ7 (LPT1), IRQ8 (RTC), SRQ9 (Unused), IRQ10 (Unused), IRQ11 (Unused), IRQ12 (Unused), IRQ13 (Math Coprocessor), IRQ14 (hard Disk Controller), IRQ15 (Unused).
Interrupt Sharing	Not Supported	Not Supported	Supported
Clock Speed	4.77 MHz	6-8 MHz	8.33 MHz
Data Transfer Rate	4.77MBps	@8MHz =16.66 MB/sec	33.32 MB/sec transfer rate for bus masters and DMA devices(But wait state, interrupts and other protocols reduces the effective bandwidth by almost half)
Back Version Support	--	Yes, also support 8 bit ISA	Yes Supports 8 Bit ISA , 16 Bit ISA and EISA
No. of Pins used	62	98	98 + 100 inlay (Total 198)
Interface

Alternate Titles:

Compare 8 bit ISA, 18 bit ISA and EISA

8 Bit ISA vs 16 Bit ISA vs EISA