An experimental minimalist emulation of Exile on the BBC Micro using Javidx9's olc 6502 emulator
Note: This project has been done for fun and educational purposes only. To actually play BBC Exile, I recommend using a full BBC emulator such as BeebEm (http://www.mkw.me.uk/beebem/) or JSBeeb (https://bbc.godbolt.org/).
One of my projects during lockdown in 2020 has been to learn 6502 assembly, and to understand the code from one of my favourite games of all time - Exile on the BBC.
To help with this, I have built a BBC micro emulator (strictly it's just an Exile emulator). I've been amazed at how little additional code is needed beyond the 6502 emulator. Currently it's around 95 lines - although this doesn't include sound or the blue background as the water level changes.
I've added this as a public repository, in case others find it useful/interesting. To use it, you will need to add a ram dump of Exile (Model B version). I used the B-em emulator (http://b-em.bbcmicro.com/) to generate the ram dump. There is also an alternative version of main.cpp in the directory that parses the Exile disassembly directly, rather than using a ram dump.
Huge respect and thanks to Peter Irvin and Jeremy Smith for creating Exile. I cannot guess how many hours I spent immersed in this game, and it still amazes me how alive the world feels.
Many thanks to everyone who has produced the excellent resources that I have used for this project, including:
Exile disassemblies:
http://www.level7.org.uk/miscellany/exile-disassembly.txt
https://github.com/tom-seddon/exile_disassembly
One Lone Coder Pixel Game Engine:
https://github.com/OneLoneCoder/olcPixelGameEngine
Javidx9's 6502 project (and accompanying YouTube videos):
https://github.com/OneLoneCoder/olcNES
Information about BBC's graphic modes:
https://www.dfstudios.co.uk/articles/retro-computing/bbc-micro-screen-formats/
A few additional notes, and limitations:
- There are no sounds. This wasn't an area of focus for me, but I am missing them!
- I'm not sure that the earthquake would be triggered - I believe this requires the interrupt to be implemented, which I haven't done
- The keys repeat too quickly - eg, when firing gun. Great for shooting quickly, but uses loads of energy
- I've made a small number of "hacky" changes to both the olc6502 and the PGE - I've marked these with TD
TGD