Description:

Overview

The original chipsets used by IBM for the AT are based on the Intel iAPX 286 system. Some additional components are taken from the MCS-80/85 system. The iAPX 286 system consists of the 80286 CPU and support chips.

The chips used in the AT were introduced by Intel at various different times over approximately a decade between 1975 and 1984. In addition there are various different revisions of a particular chip. Due to these differences, relying on a datasheet from a particular year alone, may be insufficient. One thing that should be noted is the the A on the end of a part number is significant. If you click the encyclopedia link you can find a very detailed summary of the differences between the datasheets up to 1989. Using very early versions of chips manufactured before the introduction of the AT may cause unpredictable results.

Documented parts

• (any brand) Discrete Logic
• Intel 8042 (Keyboard Controller)
• Intel 82284 (Clock Generator and Ready Interface) (known as: VLSI VL82C284 [8-10MHz '286 Clock Generator and Driver (CMOS)])
• Intel 82288 (Bus Controller) (known as: VLSI VL82C288 [6-8MHz '286 Bus Controller (CMOS)])
• Intel 8237A-5 (DMA Controller) (known as: VLSI VL82C37A [5-8MHz CMOS Direct Memory Access (DMA) Controller])
• Intel 8254-2 (Programmable Interval Timer) (known as: VLSI VL82C54A [8-10MHz CMOS Programmable Interval Timer])
• Intel 8259A-2 (Programmable Interrupt Ctrl.) (known as: VLSI VL82C59A [8-10MHz CMOS Programmable Interrupt Controller], OKI M82C59A-2 [8-10MHz CMOS Programmable Interrupt Controller])
• Motorola MC146818P (Real-Time Clock + RAM) (known as: Motorola MC146818C [Real-Time Clock + RAM], VLSI VL82C018 [Real-Time Clock + RAM])
• Texas Instruments SN74LS612N (Memory Mapper) (known as: VLSI VL82C612 [DMA address register])