Even so, the syscall handler would have been written early in the development of the x86 port, well before it was "viable" for customers. Relying on quad-word i

Even so, the syscall handler would have been written early in the development of the x86 port, well before it was "viable" for customers. Relying on quad-word instructions in hand-written assembly for such a crucial part of the OS would have meant no 32-bit support at all. That's probably not a good product decision even today, but at the time, it would have been crazy.