Frenkel

Watching @deathz0r playing my Doom port Doom8088 for the first time.

Mode Y is now supported. In 86Box emulating a 286 @ 25 MHz running timedemo 3, I get 5.940 frames per second with Mode 13h and 7.991 with Mode Y. The keys for weapon switching are now [ and ]. IDDQD, IDKFA, etc. are supported. IDRATE shows the current frames per second and IDROCKET gives every enemy a rocket launcher.

Adding new features while keeping the memory usage down is becoming a balancing act. That's why I'm holding off redefinable keys for now. But hardcoding new keys is doable. For example, I could add WASD if there is demand for it. BTW, Changing the switching weapons keys is on the to-do list. I get a higher score in timedemo 3 in 86box when compiling with gcc-ia16 optimized for size than for speed. All because of the memory footprint. And with the Watcom 16-bit build I get random freezes.

"I like to see you modern speedrunners attempt to do that at 3 fps." LOL If you could change the keyboard keys, which keys would you use? It looks like there's still some code that tries to divide by zero. That needs fixing. I'm working on getting E1M6 to run by reducing it's file size. compdj.bat is for building a 32-bit version with DJGPP. I use this build of DJGPP and that one doesn't come with make. It's nice to see the Watcom version running on a 286 with an SSD. The executable is smaller than the gcc-ia16 version, which means the Watcom version has about 45 kB more free memory to store the graphics. I use an old 100 MB hard disk and it really slows the game down. When there's not enough free memory for a texture a single color is used instead. When the sky texture is replaced by a single color, I like to think it's thunder and lightning. So it's actually a feature. :P

To celebrate Doom's 30th anniversary, here's a version of Doom8088 with PC speaker sound effects. Did you have a 286 with a sound card 30 years ago?

This is actually my fourth attempt at a 16-bit Doom port. My first attempt came after viti95 mentioned doomgeneric. My second attempt came when the source code of Vanilla Doom was reconstructed. Both attempts failed because the executables would require too much memory. Then I came across nRF52840 Doom, a Doom port that needs far less memory. That attempt failed because the code was full of platform specific code. nRF52840 Doom is based on GBADoom. So for my fourth attempt I used GBADoom. GBADoom comes with a port for Windows. I was really surprised to see how easy it was to port that code to 32-bit DOS. That code is now the basis for Doom8088. "Although it is based on prBoom, most of the engine enhancements (dehacked, limit removing etc) have been reverted back to Vanilla. This is either for memory or performance reasons." It's too bad GBADoom has removed multiplayer support and demo compatibility is broken. FastDoom replaced lots of C code by 386 assembly code written in Watcom's dialect. Rewriting that to support a 286 would take a lot of time.

Texture mapped walls, and the color of the floors and ceilings is based on the texture of the floors and ceilings. E1M1 is playable, sort of. E1M2 is a slideshow. I've made a topic about Doom8088 on the Vintage Computer Federation Forums. There are demosceners there, right? I haven't made a topic on Vogons yet. There are still some features I want to add first.

The zero divide error has been fixed in the mean time. I get almost 11 frames per second in timedemo 3 in 86box with the Mode X version and these colors. The version in which every wall is texture mapped with the same texture everywhere gets 7.5 frames per second. There are still some calculations in R_DrawColumn that use 32-bit variables and I want to replace those with 16-bit variables.

I've decreased the horizontal resolution from 120 to 60 pixels and I've made some performance improvements, but now it crashes sometimes because it's trying to divide by zero. Here are two videos of Doom8088 running in 86box emulating a 286 @ 25 MHz.

I've refactored FixedMul so it doesn't use 64-bit integers and I've replaced FixedDiv in the drawing routines by FixedMul(a, 1 / b) so it also doesn't use 64-bit integers. And now I get more than 10 FPS in timedemo 3 in 86box emulating a 286 @ 25 MHz.

Using 16-bit variables instead of 32-bit helps, but I'm not sure about 8-bit though. I've looked at some disassembled code and I've seen that it converts bytes to words. Using 32-bit variables as indices into arrays sometimes causes the compiler to crash :). I got a nice speed improvement by not bit-shifting 64-bit variables in FixedMul and FixedDiv. Not using FixedMul/FixedDiv, and thus not using 64-bit variables, also helps performance. I'm now working on potato mode in Doom8088. The view window is 240x128 pixels, but every 4 horizontal pixels are the same, so you get a 60x128 graphics mode. Using flat walls, flat sky, flat floors and ceilings I get 6.5 FPS in 86Box emulating a 286 @ 25 MHz. What's next for Doom8088? Replacing info.c by getters ;)

I think it would be funny if someone makes a pull request to add the source code of the DOS version of Doom, including the source code of DMX.

So, who's gonna make a pull request to add the recently found DOS Doom source code? :P

To celebrate 40 years of PCjr, here's a quick hack of Doom8088 with 160x200 16 color PCjr graphics. It's running in DOSBox with machine=pcjr and cycles=3000.

"Good nonsense is not bad. Edwin from Asylum writes: I've invented for the game Doom, it doesn't matter which Doom, cheats on how to fill everything up and you'll never die. You have to type HOLDA when you are playing. If you type FATTY you'll turn into a Tyrannosaurus Rex. And if you shoot a guy to death you have to type DMXXXXPIS, then you can pick up his corpse and put dynamite in the place of his heart, then the whole level will explode and you go to the next level. Type PLAYFULNESS and Cookie Monster and Big Bird will help you fight. And if you type HRTPIS you can piss on a guy, which will scorch him completely. If you type MUTANT the Teenage Mutant Ninja Turtles will help you. When you are playing, type CANDY, then you can select a picture with the mouse, then close Doom and go to Word or another program. Then type PASTE DADDY SUPERGLUE and you can print or edit the picture (depending on which program you have). Don't worry Edwin, the men in the white coats are coming."