[hyperman1]

The 8086 was based on a 64K design, with segment registers thrown in to expand it to 1M (and 640K of that 1M was reserved for RAM).

It was already clear then that 64K on its own was not enough, and the segment register twiddling to touch other 64K windows was seriously limiting.

The model was patchy from day 1, and would need serious effort to be future proof. Even if computers with 640K installed were rare, the design limitation of 640K possible RAM was clearly not enough.