Jerome Fine replies: It also depends on how much of E11 you decide to use. (a) It is possible to define and implement unused PDP-11 instruction codes that NO real PDP-11 ever uses! My first preference would be 32 / 64 Bit Integer Add / Subtract Instructions. (b) John Wilson has a DLL which allows a PDP-11 user to directly access the PC RAM: via a "register" in the I/O page. The file is EMEM.DLL (Emulated Memory). Eventually I intend to replace the uses of the "hardware MMU" in the software with the EMEM.DLL so that I don't waste the whole 8,192 bytes of the PAR devoted to the use of the MMU. It will also be much faster and can be as large as the user wants - as much memory (100s of MBytes from PC RAM:) as the PC has available for E11 to use. This would be for VIRTUAL A(100000000) in FORTRAN, something impossible with a real PDP-11. (c) The MTPS instruction could be modified to have a value that would specify E11 in addition to any other PDP-11. At present, only (b) is actually available - although this could be done in hardware for a real PDP-11 so it would not really say it is not a PDP-11/93. But (a) and (c) could also be done very easily. Does anyone else have any other requests that they consider important? Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.