I think the x2,...x9 were declared just as "documentation". Really early C didn't have any types that would get passed as anything but a single word on the stack, IIRC.
(as I was going to add before getting noprocrast-blocked)
Ha, so it doesn't matter how the function is defined! You can call any function with any arguments you want, just shove 'em on the stack and see what happens. And people say ANSI C is too unsafe ;)
(as I was going to add before getting noprocrast-blocked)