The OSI routine osi_copy64 (osi_copy64 — Move data between user and PFS buffers with 64-bit addresses) helps a PFS deal with 64-bit addresses. It takes 64-bit virtual addresses and operates in much the same way as osi_copyin and osi_copyout. osi_copy64 is a high-performance routine that does not PC into the kernel. It handles 31- or 64-bit user and PFS buffer addresses for AMODE 31 or AMODE 64 PFS callers.