https://www.xtof.info/blog/?p=985

At the beginning of the 90’s, the PC platform was often mocked by its rivals. Of course, PCs were much more powerful than, say, an Amiga 500. But the Amiga offered a flat memory address, while a DOS program could only access memory using cumbersome 64 KiB segments. And to add insult to injury, there was this strange 640 KiB memory limitation. No matter how much physical memory you had in your box, the utter most important Conventional Memory was limited to 640 KiB!

The Legend teaches us that Bill Gates once declared that “640 KB ought to be enough for anybody“, then designed MS-DOS to enforce this limitation.

The truth is of course a little more complicated than that.