But the 1MB limit for address space was the hard constraint. 640kb was not a number invented out of the blue by some MS designer. It could have been 800kb or 90

But the 1MB limit for address space was the hard constraint. 640kb was not a number invented out of the blue by some MS designer. It could have been 800kb or 900kb, would that make a difference? Also, 8086 and 8088 had no MMU afaik.