You can add a number of different devices to the sim.ini configuration file and the baseline RSX system will recognize some of them. The most important thing to add to your system is some DZ11 terminal lines as simh will let these be connected via telnet on port 10001 in a system after SYSGEN. Once you have finalized a selection of hardware for your system you will want to customize your RSX system for that specific hardware through a process known as SYSGEN. The hardware you choose will have a CSR and a VECTOR address that you will be asked for during SYSGEN. You can usually take the default values offered by the SYSGEN process. Also, the SYSGEN saves your responses in three files; SYSGENSA1.CMD SYSGENSA2.CMD and SYSGENSA3.CMD These can be created with SYSGEN then edited so you can change the answer to a simple like the system name or a CSR or Vector. If you forget to add a device you should rerun the SYSGEN. Also, it is possible to change the CSR and vector for hardware in an RSX11M system with the Configuration (CON) utility.
In appendix F is an example SYSGEN dialog to guide you. To start you boot your new baseline system which we shorted the filename to rsx11mp.dsk with simh. The pdp emulation you use to run the SYSGEN does not matter, but once done the rsx11mp.dsk will have a new version of RSX11M+ that is customized with your hardware choices. Once you have booted the system you should be in the [200,200] directory where the SYSGEN.CMD script file is located. To run a RSX script also known as a command file type @filename.
Appendix F has the dialog of the example SYSGEN process. After answering various questions about options for the operating system and the hardware, the SYSGEN process provides an opportunity to edit the saved answer files, then you rerun the @SYSGEN to use the saved answer files to drive the actual compiling and linking of the operating system, and its drivers. At the end of that process there is a RSX11M.TSK in directory [1,54] At this time the SYSGEN will automatically run a process known as VMR which builds the final RSX11M.SYS operating system. The final step is to boot the new operating system. If you asked for XDT the executive debugging tool, a XDT> prompt will come up to which you type G for GO and the newly created system will boot up. At that point you must now SAVe the system with the SAV command and use the /WB option to point the disk's boot block to your new system.
This RSX SYSGEN process is described in a number of references on the Internet but all of the actual RSX documentation can be found at http://bitsavers.trailing-edge.com/pdf/dec/pdp11/rsx11/RSX11Mplus_V4.x/ Also, at that site you will find the RSX11M+ mini reference which has not been changed since version V4.2 It is the best single reference on using the system.
RSX11M+ was the final and most sophisticated PDP-11 operating system supporting real-time data acquisition as well as time-sharing capabilities. With 4 MB of memory it could easily handle 20-30 users doing a range of editing and compiling, with batch queues for low priority scheduled jobs, while handling high priority real-time tasks. It had a large number of programming languages (F77, BasicPlus2, Macro-11, C, APL, Datatrieve-11, and others) and sophisticated networking (DECnet). My PDP-11/70 (DECdatasystem 570) front panel was taken from a system that made banking transactions for a New York Wall Street firm. It now once again displays the characteristic LED light pattern that RSX displays when idling, which you can see in some YouTube videos.