Every civilization believes its walls are the edge of the universe. The 8088 was the first to be technically correct.
The Intel 8088 processor addresses memory through a 20-bit bus. Twenty bits. This is not a design choice — it is cosmology. Twenty bits yield 1,048,576 addressable locations, each one byte wide, each one as real as a plot of land in a country where the surveyors have counted every grain of soil. Of these million-and-change addresses, IBM’s engineers — men in short-sleeved shirts who believed they were building a business machine and were in fact founding a civilization — reserved the upper 384 kilobytes for system use: video memory beginning at A000h, the ROM BIOS enthroned at F000h, and various hardware adapters staking claims in the C000h-EFFFh frontier like prospectors filing deeds. What remained was 655,360 bytes. The 640K. The world. Programs born into conventional memory do not understand the number 655,360 the way you understand it — as a limitation, a constraint, a punchline in the history of computing. To them it is the distance between 0000:0000 and 9FFF:000F, and that dista...
From the lore of Conventional Memory.