Alastair Bridgewater wrote an microcode emulator for the Explorer I (E1) cpu in common lisp. It's made a lot of progress and will now run diagnostics and lisp code.
According to Alastair,
The Nevermore system is, at present, an experimental simulator for the Explorer I (Raven) microcoded CPU. It is hoped that sufficient progress will be made that some other pieces of Explorer hardware can be simulated as well.
The original core of this project was the result of my desire to have a working disassembler for the Raven microcode. After my second attempt in C, I realized that the best output format would be as close to the original input format as I could manage. The third attempt was again in C, and ran afoul of the list and symbol manipulation required when putting together a prototype for such a disassembler. The fourth attempt was written over the course of Nov. 7 through 9, 2003 in CMUCL. This was successful enough that over the Sunday and following Monday I was looking through the disassembly of the boot PROM and figuring out how certain parts of the code functioned.
Hello all, As advertised, I am releasing a new version of Nevermore after nearly a year and a half. ...
This version passes all but four of the EXPT diagnostics (I-MEMORY, UNMAPPED ACCESSING, EVENT POSTING, and MEMORY CYCLE ABORT, if you're wondering), and contains a couple of new interface bits over the previous release (documented in the README). In order to run Nevermore, you will require a disk image and ROM set. If you can run Meroko you should have everything you need to run Nevermore, if not necessarily in the right format. There is one error in the startup process listed in the README. Before you begin, edit load-romfiles in romload.lisp, and fix the path to the CPU config ROM. (had to be one stupid bug in the release, right?) Anyway, that's enough blather, download and enjoy! --Alastair Bridgewater
A large amount of E1 documentation on bitsavers.org
Alastair's pastes (development notes):
... these pages (generated-with-lisp) ...