industry standard architecture (PC) (ISA)
The Industry Standard Architecture(ISA) forms the guideline for PC and software manufacturers in which the properties of AT PCs are specified.
The ISA architecture defines the central processing units( CPU), the properties of operating systems, the I/O bus and the system bus. The I/O bus was designed for the CPU 80286, it has 16 data and 24 address lines.
The slot for the ISA bus consists of two separate slots: an 8-bit slot with 62 contacts and a slot for the 16-bit expansion with 36 contacts. The 8-bit slot corresponds to the older XT bus. The clock frequency is 8.33 MHz and the data rate is 8.33 MB/s. The 16-bit bus, which operates synchronously with the division of the CPU clock, has 98 contacts.
The Line Printer Terminal( LPT), the COM ports, the floppy drive and the keyboard are connected to the ISA bus. ISA plug-in cards, such as Soundblaster and sound cards, can be operated in the ISA bus.
The ISA standard adopted in 1981 was extended to Extended ISA( EISA) in 1988. Furthermore, based on the ISA standard, various industrial bus systems were developed. So the ISA96, AT96, PC/104 etc. which were based on the CPUs x86 and found their use in industrial applications.