AMD64:

scratch:
rax	(1st return)
rcx	(4th arg)
rdx	(3rd arg, 2nd return)
rsi	(2nd arg)
rdi	(1st arg)
r8	(5th arg)
r9	(6th arg)
r10	(temp, static chain?)
r11	(temp)

preserved:
rbx	(base pointer)
rsp	(stack)
rbp	(frame)
r12-r15	(general)

calls:
rdi	1
rsi	2
rdx	3
rcx	4
r8	5
r9	6

return:
rax	1
rdx	2

I386:

scratch:
eax
ecx
edx

preserved:
rbx	(pic base register, preserve for call)
rsp
rbp
esi
edi

return:
rax	1
rdx	2