Parity -

Until the 100 MHz 486's and Pentiums, all IBM's required a parity chip, which raised the cost of the RAM chip, but assisted in the Power On BIOS (Basic In Out System) tests. Most of the Bios manufacturers required the parity chip to compare the other chips in that bank to it. If a chip didn't match, the system stopped, beeped, and flashed an error message... stating the RAM failed the parity check. Many new systems no longer use the parity test, and therefore don't use parity chips. If you are getting RAM from a place different than where you are getting the motherboard, this section is very important!