A few years ago i bought a couple of old PCs from ebay, one being an original IBM PC, the other some unknown 286-based PC, so i decided to create some stuff for

A few years ago i bought a couple of old PCs from ebay, one being an original IBM PC, the other some unknown 286-based PC, so i decided to create some stuff for it. One thing i wrote was a 3D maze and of course i wanted to make it run at interactive levels on the IBM PC's 4.77MHz CPU. Initially i wrote a map editor and an initial implementation in QBasic which, of course, was far from fast but it allowed me to find some algorithm to display a simple first person maze. Then i ported it to Turbo C which made it faster, but again it was too slow. After several optimizations, i ended up writing a machine code generator for rendering the vertical spans (this was one of the slowest parts) which made it to draw the maze almost instantly in the 286 with its "turbo" mode turned off [1]. The IBM PC wasn't working at the time (i had to buy a few more components to make it work) but once i fixed it, i tried the maze and after a few tweaks it worked there too [2] (sadly no video). The generated code actually draws four spans in one go (since CGA packs 4 pixels in a byte) so you first get a coarse frame of the walls that is quickly "patched" with some C code to fill the few pixels that would differ and smooth it out. I found it amusing that it takes almost as much time to fill the entire wall as to patch out the few pixels. I hadn't written any program that generated its own code before and i found it very interesting. And felt a bit sad that this sort of optimization isn't really needed much anymore (in the stuff i am working on anyway). [1] https://www.youtube.com/watch?v=tfbQIvRYph4 https://www.youtube.com/watch?v=tfbQIvRYph4 [2] https://i.imgur.com/M3gKlfA.jpg https://i.imgur.com/M3gKlfA.jpg