Big Kudos to
- Bob Supnik for his Computer History Simulation Project. His PDP-11 simulator in the simh suite is the best open source PDP-11 simulator. It is the authoritative behavioral model of various PDP-11 processors written in C.
- Tristan Gingold for ghdl, the best and most complete open source VHDL simulator.
- Al Kossow for his site bitsavers.org, a comprehensive source of documentation of old computers and their software, see the list given under 'Original Documentation'.
- Steven Schultz for his decade long effort to maintain 2.11BSD UNIX. 447 patches accumulated 1991 to 2009 in the 2.11BSD patch archive.
Other important factors were
- gtkwave, a waveform viewer. Well integrated with ghdl, goes beyond VCD limitations, gives access to VHDL record or enumeration types.
- the tuhs and pups archives of historical UNIX systems.
- Jiri Gaislers VHDL design approach (see paper and presentation). Many w11 modules are implemented in Jiri's two-process design methodology and make heavy use of VHDL records, within entities but also in interfaces. The best example of this methodology is Jiri Gaislers's LEON3 implementation, another is for example the MB-Lite core on OpenCores.