Almost all the PC's made before 1997, have a few Industry Standard Architecture (ISA) slots. It is recognizable by its brown or black color and has two parts, a shorter part and a longer part.
Few motherboards until recently had slots for older ISA plug-in-cards. This way the older 8-bit and 16-bit ISA and 32-bit EISA can still be used on these PCs. These slots are now obsolete.
The 8-bit ISA bus operated at 4.77 MHz, while the 16-bit bus operated at 8 MHz. IBM replaced the ISA bus with their proprietary Micro Channel Architecture (MCA). The system was far more advanced than ISA, and computer manufacturers responded with the Extended Industry Standard Architecture (EISA) and later, the VESA Local Bus (VLB).
