I tried out the emulator for the MIT CADR mentioned in P2879 on a Linux machine. Since it's based on SDL, it needs a direct console or X running directly on the console - it's not network transparent. But otherwise: really excellent. Ok, boot takes forever, but once it has booted, the response time on an approximately 1 GHz Epia is quite acceptable. Optimize the code a bit, get a somewhat more powerful machine and you have a nice historical CADR running. Without having to revive the old hardware. Just beautiful. You get directly into the normal system and have the entire screen for a large listener. With the system menu you can then split the screen into editor windows (with the good old ZWEI) and listener (the Lisp prompts). Mail is included, Telnet and a few more tools for Lisp development. Very nice, the whole thing.
The keyboard emulation is still problematic - you can hardly find special characters. The special characters are oriented towards American keyboards, the normal letters on the other hand to the local keyboard mapping, but not all keys are functional - the umlaut keys of the German keyboard produce breaks, but don't deliver the special characters that actually lie on them and are thus missing.
Besides, the mouse still has serious problems: the area where it can move gets smaller and smaller, so it becomes increasingly difficult to click anywhere.
Otherwise though, really impressive work overall. This could turn into a really nice thing, even if the machine uses not Common Lisp but one of its many predecessors.
If anyone starts it directly from the console without X, don't be alarmed: the special characters are ok. SDL uses AA-Lib internally and thus emulates the graphical elements with characters on the text console. A bit unusual, but quite usable if you don't have X at hand at the moment.
By the way, after startup the machine seems to calculate in the octal system. A (5 6) gives 36 and a (3 4) gives 14. You can probably set the base somewhere for how numbers are displayed. My Symbolics manuals (the Symbolics and the CADR are related) didn't provide anything directly, but I also didn't feel like rummaging through 1 meter of paper.