I have an interesting hardware question. I have been looking at the results for the program RESORC.SAV in RT-11 with respect the MFPT instruction. When the J11 chip is used, the value is 5 and the Maintenance Register at 177750 seems to determine what the rest of the actual hardware supports. I thought it would also be helpful for the user to know if an emulator is being used, either software or hardware, or if perhaps some other 3rd party hardware CPU. I would probably target the various 3rd party boards as far as hardware is concerned (such as QED and Mentec). For software emulators, I would suggest that only the high end PDP-11 processors be supported (the DEC CPUs which support the MFPT instruction) in order to keep things simple, at least initially. An incomplete list of software emulators is: SIMH Ersatz-11 An incomplete list of hardware boards is: QED - more than 1? Mentec - at least 3 and I can remember at least 2 others, but not the company names. Right now the Logical Co. has a combined emulator called a PDQ-1000 board which actually plugs into a Qbus which takes only 4 slots, but includes CPU, memory and many controllers. Thus far, the high order byte of the MFPT instruction always seems to be zero and is currently ignored by the RESORC.SAV program. Under SIMH and Ersatz-11, it would be trivial to use the high order byte of the MFPT instruction to signify which software emulator is being used. Can anyone who has a DEC (or non-DEC) PDP-11 system easily available determine the actual value returned by the MFPT instruction? As far as I know: MFPT Value Hardware 1 PDP-11/44 3 PDP-11/24 (should be 2) 3 PDP-11/23 4 SBC-11/21 5 All J11 chips including 11/73, 11/83, 11/93 I assume that it would be extremely difficult, probably not worth the effort, to modify the high order byte of the MFPT instruction at this point for the 3rd party PDP-11 CPU boards, such as from Mentec. Can anyone comment on this assumption? Might there be another way for hardware to the tell a user which 3rd party board is being used as a PDP-11? The other possibility is to use the Maintenance Register at 177750, although I suspect that there might not be any more bit available. Jerome Fine