The 16-Bit Decision That Became a 64-Bit Problem

How did a tiny decision made in 1978 become a problem that still exists inside modern 64-bit computers? This video tells the surprising history of the A20 line — from Intel’s 8086 and IBM’s original PC to the 80286, DOS, HIMEM.SYS, and modern x86-64 processors. A simple compatibility problem led IBM engineers to create a temporary hardware fix using a spare pin on the keyboard controller. Decades later, that legacy is still part of the way x86 computers boot. This is the story of how a small engineering shortcut became one of computing’s longest-lasting pieces of legacy technology. #ComputerHistory #Intel #IBM #64Bit #x86 #TechnologyHistory