Adam Mayer reverse-engineered the VT100 firmware and added some patches for the 2014 Retrocomp. It's crazy and fun! For some details regarding the ROMs and the VT100-Hax Emulator, read on.

Dumps of the four original 2Kb ROMs containing the firmware for the VT100's 8080 CPU were originally available as early as 2004 at http://www.dunnington.u-net.com/public/DECROMs/.

The VT100 firmware ROMs are:

• 23-061E2.bin
• 23-032E2.bin
• 23-033E2.bin
• 23-034E2.bin

Another important VT100 ROM is the Character Generator ROM, a 2Kb ROM containing 16 bytes of "font" data for each of the 128 characters. However, this ROM wasn't needed for the challenge, and it isn't used by the VT100-Hax emulator.

• 23-018E2.bin

Unfortunately, the above website is not currently available, but it's still accessiable via the Wayback Machine. Information from that website has also been preserved at pcjs.org and on GitHub.

To create a single 8Kb ROM image from the four 2Kb ROMs:

cd ROMs
cat 23-061E2.bin 23-032E2.bin 23-033E2.bin 23-034E2.bin > basic.bin

To disassemble the ROM, use dz80 from D52 (here's the manual):

dz80 -80 basic.bin

This produces basic.d80. To reassemble, use asm8080. But first, replace references to X2000 with 2000h, and pad the image to 8K by replacing the final nop with:

org	1fffh
nop

Now you're ready to (re)assemble:

asm8080 -lbasicnew -obasicnew basic.d80

The assembler should produce basicnew.bin and basicnew.lst, and the new bin file should be identical to basic.bin.

You'll probably want to use the ncurses-based emulator, since the Qt-based emulator is still a work-in-progress.

The ncurses Makefile was slightly modified for use in OS X, because the C/C++ compiler that Apple now includes doesn't support variable-length array declarations. The simplest solution is to install a newer version of GCC using Brew:

brew install gcc

As of this writing, Brew installs GCC v6.x and creates symbolic links such as gcc-6, g++-6, etc.

So the Makefile invokes g++-6 instead of g++ for .cpp files and gcc-6 for .c files, since the 8080 emulation C code is referenced by the VT100 simulation C++ code as extern "C".

cd emulator/ncurses-vt100
make
vt100sim --run ../../ROMs/basic.bin

The emulator starts a bash process and connects its I/O to the simulated VT100 terminal. Press F10 to switch between TYPING mode and CONTROL mode.

In CONTROL mode, you can press:

• space to start/stop
• b to set a breakpoint
• d to delete a breakpoint
• m to snapshot memory
• n to single-step
• q to quit

In TYPING mode, these keys are remapped:

• F6 is BREAK
• F8 is ESC
• F9 is SET-UP

Note: the 8080 emulation code is based on the Z80-CPU simulator written by Udo Monk.