Intel 8284

The Intel 8284A situated on a motherboard next to a crystal oscillator.

Intel 8284 pinout in a 18-pin DIL package.

The Intel 8284 is a clock oscillator chip developed primarily for supplying clock signals for the Intel-8086/8087/8088/8089 series of processors. The commercial variant of the chip comes in 18-pin DIL and 20-pin PLCC packages, and originally was priced at $4.90 USD. The industrial version, rated for more extreme temperatures and supply voltages, was priced at $13.50 USD.^[1][2]

Function

The 8284 contains a clock generator capable of a third the frequency of the input clock (up to 8MHz with the 8284A), with sources selectable between an external crystal and clock input. The main clock output consists of a 4.5V (Vcc @ 5V) square wave at a 33.3% duty cycle, with an additional peripheral clock running at half of the main clock and a 50% duty cycle. Additional logic is provided to accommodate delays to allow for proper system start-up. It has been used in the IBM PC and IBM PC XT.

References