It seems adding an instruction like IPF's EPC might accelerate certain system calls by allowing a user process to jump directly to a specific supervisor function (avoiding the generic syscall interface and potentially several intermediate steps). Since embedded system code is relatively small, the syscall targets could easily be encoded in the immediate offset of the JumpAndLink instruction. Unlike the Itanium's EPC, OpenRISC's version could perform some simple operation (perhaps an addition like SPARC's register window adjustment instruction) in addition to the privilege escalation. OTOH, this would not greatly speed syscalls; OTOH, it might not be that expensive to implement either. Paul A. Clayton -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.opencores.org/forums/openrisc/attachments/20041029/c84910da/attachment.htm