The original Xbox (NTSC-U) release of Need for Speed: Underground, lifted instruction by instruction to C and running natively, with no emulator.
Features · Playing on Switch · Building · Configuration · Status
Important
No game data is included. You need your own copy of the Xbox disc,
extracted (default.xbe, FRONTEND/, CARS/, ...).
- 🏁 Native code: the whole game runs as recompiled C, built with xboxrecomp
- 🎮 Two renderers: Vulkan (NVK on Switch, recommended) and OpenGL, with render scaling up to 4x
- ⚡ 30 fps races on Switch (the game's own cap) with the Vulkan build and raised clocks
- 🪞 Car reflections as cube maps (Vulkan), switchable in Options → Camera → Car Reflections; Off also skips the reflection cube-face passes in races
- 🖼️ Cleaner picture (Vulkan): mipmaps with trilinear and 16x anisotropic filtering, FXAA, square-pixel 1280x720 for the 16:9 view
- ⚙️ Graphics options in the game (Vulkan), under Options → Camera:
Resolution Scale (1x, 1.5x, 2x, 2.5x), Anti-Aliasing, Anisotropic
(Off-16x) and Square Pixels, applied at once and kept in
nfsu1x_options.txt - 🎬 Movies played by the game's own EA
.maddecoder - 🔊 Audio through an emulated Xbox APU, with 5.1 downmixed to stereo
- 📳 Rumble on Switch HD rumble and SDL controllers
- ⏱️ CPU/GPU/memory clocks settable per mode (handheld and docked), kept across dock changes, HOME and sleep
- Shares its runtime with the Underground 2 port
- Copy the NRO to
sdmc:/switch/nfsu1x/(nfsu1x-vulkan.nrofor the Vulkan build,nfsu1x.nrofor OpenGL). - Copy the extracted disc (not the ISO) to
sdmc:/switch/nfsu1x/game/. - Start it with title takeover: hold R while launching any game. Applet mode leaves too little memory.
sdmc:/switch/nfsu1x/
├── nfsu1x-vulkan.nro
├── nfsu1x_env.txt optional settings, KEY=VALUE per line
├── nfsu1x_options.txt written by the in-game options the port adds
├── save/ created on first run
└── game/
├── default.xbe
└── ...
Buttons map by label (Switch A = Xbox A). Settings go in nfsu1x_env.txt
(see Configuration) and the log is written to the
same folder.
Recommended nfsu1x_env.txt:
RECOMP_GIL_EAGER=1
RECOMP_CULL=0
RECOMP_GL_SCALE=1.5
NFSU2_CPU_MHZ=1785
NFSU2_GPU_MHZ=7681. Extract the disc and lift the XBE to C
python3 -m tools.xiso unpack "Need for Speed - Underground (USA).iso" /path/to/game # from xboxrecomp/
# Writes NFSU1_GEN_DIR (default /root/nfsu1x/gen)
NFSU1_XBE=/path/to/game/default.xbe NFSU1_GEN_DIR=/path/to/gen tools/regen.sh2a. Linux (SDL2 + OpenGL or Vulkan)
cmake -S . -B build -G Ninja -DNFSU2_GEN_DIR=/path/to/gen # add -DNFSU2_VULKAN=ON for Vulkan
cmake --build build
NFSU2_GAME_DIR=/path/to/game build/nfsu2_recomp2b. Nintendo Switch (devkitA64, switch-sdl2, switch-mesa)
NFSU2_GEN_DIR=/path/to/gen NFSU2_GAME_SRC=/path/to/game switch/build.sh
# Vulkan build (needs mesa-switch NVK and glslang for Switch)
VULKAN=1 JOBS=6 NFSU2_GEN_DIR=/path/to/gen switch/build.shCMake options and most runtime switches keep their NFSU2_* names: the glue
code is shared with the Underground 2 port.
| Path | What |
|---|---|
src/main.c |
boot and runtime defaults |
src/recomp_manual.c |
hand-written overrides of lifted functions (D3D, DirectSound, CRT) |
src/switch_nx.c |
Switch log device, env file, clocks, profiler, loading screen |
config/seed_functions.json |
entry points the static pass cannot see |
xboxrecomp/ |
the toolkit (MIT), vendored with this port's changes: NV2A renderers (Vulkan, OpenGL), SDL audio, Switch platform layer, translator fixes |
tools/regen.sh |
XBE → lifted C (gen/, never committed) |
tools/prof_report.py |
Switch profiler (prof.bin) → per-thread function tables |
switch/build.sh |
Switch NRO build + SD-card staging |
On Linux these are ordinary environment variables. On the Switch they go in
sdmc:/switch/nfsu1x/nfsu1x_env.txt, one KEY=VALUE per line (# starts a
comment). The Underground 2 README
lists every runtime switch; the ones that matter here:
Performance and clocks (Switch)
| Variable | Meaning |
|---|---|
NFSU2_CPU_MHZ, NFSU2_GPU_MHZ, NFSU2_MEM_MHZ |
Clocks (closest listed rate, capped at 1785 / 921.6 / 1600 MHz). The CPU is what limits the port. Old rates come back on exit. |
NFSU2_CPU_MHZ_DOCKED, NFSU2_GPU_MHZ_DOCKED, NFSU2_MEM_MHZ_DOCKED |
Different rates while docked (otherwise the plain keys apply in both modes). |
RECOMP_GIL_EAGER=1 |
Hand the guest lock over by guest priority (the main thread pre-empts workers). |
RECOMP_CULL=0 |
No off-screen batch culling (in NFSU1 it costs more than it saves). |
RECOMP_VK_INSTANCE=0 |
Vulkan: don't merge repeated draws into instanced draws. |
RECOMP_GL_THREAD=1 |
OpenGL: GL calls on their own thread. |
RECOMP_NX_PROFILE |
Sampling profiler into prof.bin: 1 = busy threads, 2 = every thread above 2%. |
NFSU2_NO_LOG=1 |
No log file, no [perf] reports, no profiler. |
Graphics
| Variable | Meaning |
|---|---|
RECOMP_GL_SCALE |
Render resolution multiple, 0.5..4 (fractions allowed). Vulkan: only until Options → Camera → Resolution Scale is changed (default there 1.5x). |
RECOMP_GL_SCALE_X |
Vulkan: horizontal multiple, if different; overrides Square Pixels. |
RECOMP_VK_MIPS=0 |
Vulkan: no mipmaps (distant textures shimmer, the old look). |
RECOMP_VK_ANISO |
Vulkan: anisotropic filtering, 1..16 (default 16; 1 = off). |
RECOMP_VK_LOD_BIAS |
Vulkan: mip bias, negative = sharper (default -0.25). |
RECOMP_VK_FXAA=0 |
Vulkan: no FXAA (plain scaled blit to the screen). |
RECOMP_VK_CUBE=0 |
Vulkan: no cube maps (car reflections off), whatever Options → Camera says. |
RECOMP_GL_DXT=0 |
Decode DXT textures on the CPU instead of uploading them compressed. |
RECOMP_GL_TEX_MB |
Texture cache budget in MB. |
RECOMP_PROG_CACHE |
Shader/pipeline cache file (progcache.bin), =0 off. |
RECOMP_GL_DUMP=<prefix>[,every] |
Write presented frames as BMP. |
RECOMP_FPS_LOG=1 |
Presented frames per 10 s. |
RECOMP_DRAW_STATS=1 |
Vulkan: draws → draw calls per frame. |
Game, audio and input
| Variable | Meaning |
|---|---|
NFSU2_GAME_DIR |
Extracted disc (Linux; default ./game). The Switch always uses sdmc:/switch/nfsu1x/game/. |
NFSU2_GL=0 |
Use the executor's CPU renderer instead of the GPU renderer. |
NFSU2_FPS_CAP=30 |
Keep the game's 30 fps cap (default: uncapped, up to 60 fps). |
RECOMP_AUDIO_VOLUME |
Master volume 0..100 (default 50). |
RECOMP_AUDIO=0 |
No host audio device. |
RECOMP_PAD_SCRIPT |
Timed presses, e.g. 4000:start:300,9000:a:200 (ms from the first pad read). |
RECOMP_PAD_LAYOUT=position |
Map buttons by position (Xbox layout) instead of by label. |
RECOMP_RUMBLE=0 |
No rumble. |
NFSU1_AUTOLOAD=1 |
At boot, load the most recent saved profile straight away (no "load?" questions) when there is one. |
| Platform | State |
|---|---|
| 🐧 Linux | Movies, title, menus, Quick Race at 30 fps with HUD, AI and audio |
| 🎮 Switch hardware | Menus and Quick Race at 30 fps (Vulkan, CPU 1785 MHz) |
Still open: the main-menu car's rear window shows through its side windows; cube maps on OpenGL; Career mode untested.
CLAUDE.md: detailed engineering notes (address map against Underground 2, fixes, performance measurements)
Need for Speed and Underground are trademarks of Electronic Arts. This is
an unofficial fan project, not affiliated with or endorsed by EA or Microsoft.