Demon's Souls — native PC port (ps3recomp)

A native Windows build of Demon's Souls (PS3, USA, BLUS-30443), made by statically recompiling the game's PowerPC (PPU) and SPU code to C/C++ with ps3recomp, plus a PS3 runtime and a Direct3D 12 renderer. It is not an emulator: the game's code runs as a normal x64 program.

No game files are included. This repo holds only the tools, patches and build scripts. You need your own copy of the game, dumped from your own disc. The setup reads your disc image and builds everything on your PC.

Status

The entire game seems playable. It runs with sound and music at 60 fps (or 50 on a 100 Hz screen, 30, uncapped, or any frame rate you pick), with keyboard + mouse or an Xbox controller. Intro movies are skipped and there is no online play.

I'm currently playing through the whole game to find and fix any spots that still run slower than they should (stutters, frame drops in heavy scenes). Boletarian Palace, the heaviest area tested so far, is already smooth. Expect more performance fixes as the playthrough goes on; see docs/NOTES.md for the full development log (50 fixes and counting).

If you hit a stutter or a crash, please report it: see Reporting stutters and crashes. Every run is recorded, so all it takes is pressing F8 when it happens and running REPORT.bat afterwards.

What you need

• Windows 10/11 x64 and a Direct3D 12 GPU. AVX2 (Intel Haswell / AMD Ryzen or newer) is used when your CPU has it; on older CPUs BUILD.bat builds without it (a couple of fps slower in the heaviest areas).
• About 12 GB free disk space (8 GB game files + build).
• Your disc image of Demon's Souls USA (BLUS-30443): a .iso (a Redump .zip works as is), or a dumped disc folder with PS3_GAME in it. A Redump-style encrypted image also needs its disc key (the .dkey file that comes with the dump, or the "Disc Key" on its Redump page).
• RPCS3, used once to decrypt the game's EBOOT.BIN. Unzip it anywhere.
• Python 3.10+ and Git. If they are missing, SETUP.bat offers to install them with winget.
• Visual Studio 2022 (Community or the free Build Tools) with Desktop development with C++, and LLVM (clang-cl) 17 or newer. If they are missing, setup offers to install them with winget.

Build it (one time)

1. Download this repo (green Code button → Download ZIP, or git clone) and unpack it somewhere with enough space, ideally a path without unusual characters.
2. Drag your disc image onto SETUP.bat, or double-click SETUP.bat and it asks for it.
3. Answer its questions: the disc key if the image is encrypted, and where rpcs3.exe is.

That's it. SETUP.bat then:

step	what happens	time*
1	extracts all game files from the image (and decrypts them) into game/	2–5 min
2	decrypts EBOOT.BIN → EBOOT.elf with RPCS3 and checks it is the tested version	< 1 min
3	downloads ps3recomp at the tested commit and applies this port's runtime patch	< 1 min
4	recompiles the game: ~94,000 PPU functions + 12 SPU programs → C/C++ in port/	2–4 min
5	applies this port's edits to the recompiled code (patches/lifted-code.patch)	seconds
6	compiles everything with clang-cl into port/build_opt/DemonsSoulsRecomp.exe	10–30 min

* on a fast 16-core PC; the first compile is the long part. If anything fails, fix what it says and run SETUP.bat again: finished steps are skipped.

Play

Double-click PLAY.bat. The logos and first load take about a minute.

launcher	what it does
PLAY.bat	60 fps (50 fps automatically on a ~100 Hz monitor, every frame shown exactly 2 refreshes)
PLAY_30FPS.bat	the original 30 fps
PLAY_50FPS.bat	50 fps locked to a 100 Hz screen
PLAY_UNLIMITED.bat	uncapped (up to 240 fps), no vsync, game speed stays correct
PLAY_CHOOSE_FPS.bat	a menu of the above, plus any frame rate you type in (31–240)
PLAY_REMASTER.bat	runs with the PC Remaster mod installed (see below)
PLAY_DUMP_TEXTURES.bat	saves every texture the game draws, for texture packs (see below)

Custom frame rate. PLAY_CHOOSE_FPS.bat → 6 → type a number, e.g. 45, 72, 120 or 144. The game runs at real speed at any of them. If your monitor's refresh rate is a whole multiple of the number (72 or 144 on a 144 Hz screen, 40 or 120 on 120 Hz), every frame is shown for the same number of refreshes and motion is perfectly even. Otherwise vsync is turned off, which looks fine on a G-Sync / FreeSync screen but can tear on others. The launcher says which one you got. You can also set DES_FPS=<number> before running PLAY.bat.

Controls. An Xbox (XInput) controller works when plugged in (A = Cross, B = Circle, X = Square, Y = Triangle, LB/RB = L1/R1, LT/RT = L2/R2, Back = Select). A DualShock/DualSense needs Steam Input or DS4Windows. Keyboard + mouse:

WASD	move
mouse (or IJKL)	camera
left mouse	attack (R1)
Shift	strong attack (R2)
right mouse	block (L1)
Ctrl	parry (L2)
Space	roll / dash / back (Circle)
E	interact / confirm (Cross)
F	two-hand (Triangle)
R	use item (Square)
Tab / middle mouse	lock on (R3)
arrows	d-pad (switch items)
Enter / Backspace	Start / Select
F1	capture / release the mouse
F9	god mode on/off (no death, HP/MP/stamina stay full)

At Create Profile a text box opens for the character name. Saves go to gamedata/. Each run writes logs to logs/ (they grow by ~600 MB an hour; the previous run is kept as *_prev.txt).

Reporting stutters and crashes

Every launcher records frame timing while you play (about 25 MB an hour, no visible cost; the newest 10 sessions are kept in perf\). The window title shows [RECORDING - F8 = stutter, N marked].

1. Press F8 in the game right after you see a stutter, hitch or slowdown. Each press puts a mark in the recording at that moment, so the exact frames can be found later. Press it as often as you like.
2. After you quit (or right after a crash), double-click REPORT.bat. It packs the last session into one zip, shows it in Explorer and opens the GitHub New issue page.
3. Open an issue with the Stutter / slowdown or Crash / bug template, drag the zip into it, and say where you were in the game and what you saw at each F8 press.

What the zip contains (nothing else, and your Windows user name is removed from all of it):

file	what it is
report.txt	the summary from tools/perf_report.py: frame pacing, every hitch with its likely cause (a slow game step, shader compile, slow file read, the renderer, the GPU), and what happened just before each F8 mark
perf.txt	the recording itself, so we can dig into the exact frames (trimmed to the minutes around your F8 marks if the session is too long for GitHub's 25 MB limit)
system.txt	Windows version, CPU, RAM, GPU + driver, monitor resolution / refresh, the frame-rate setting and which version of this port you built
log_tail.txt	the last 400 lines of the game's log, from the same session (shows what it was doing if it crashed)

Curious yourself? .venv\Scripts\python tools\perf_report.py prints the same summary for your newest recording. To play without recording, set DES_RECORD=0 before running a launcher.

Optional: PC Remaster mod

The Demon's Souls PC Remaster mod by fromsoftserve (Nexus Mods, Demon's Souls mod 106) (made for RPCS3) works with this port. Download the mod's zip yourself, then:

.venv\Scripts\python tools\install_remaster.py "path\to\the mod.zip" --apply

That builds game_remaster/ as a hard-linked copy of game/ (no extra disk space) with the mod's files swapped in. Your normal game/ is not changed. Play with PLAY_REMASTER.bat.

Optional: texture packs

Textures can be replaced without unpacking any game files, at any resolution:

1. Run PLAY_DUMP_TEXTURES.bat and play through the part you want to change. Every texture the game draws is saved once to textures\dump\ as <KEY>_<width>x<height>_<format>.png, exactly as it looks in game. The 16-character KEY comes from the texture's contents, so it is the same on every PC.
2. Edit a PNG (or make a bigger one) and put it in textures\replace\ with a name that starts with the same KEY, e.g. 0123456789ABCDEF_armour_4k.png. Sub folders are fine.
3. Start any launcher. Replacements load in the background; .dds files (DXT1/3/5, BC7, BC4 or 32-bit RGBA, with or without mipmaps) load faster and use less video memory than PNG.

Details and settings: textures\README.txt. Cubemaps (reflections) are not covered; models are file mods (see the PC Remaster section). Packs are made from the game's art -- share them only where that is allowed.

Repo layout

SETUP.bat / BUILD.bat        one-time setup / rebuild after code changes
PLAY*.bat                    launchers (environment switches documented inside PLAY.bat)
REPORT.bat                   packs the last session into a zip for a GitHub issue
setup/setup.py, build.py     the setup pipeline and the toolchain finder + build
project/                     CMake project: CMakeLists.txt, main.cpp, stubs.cpp
patches/ps3recomp-local.patch   this port's changes to the ps3recomp runtime/renderer (applied to
                                ps3recomp @ 4e8f3ca, v0.18.0)
patches/lifted-code.patch    this port's edits to the recompiled game code (frame pacing, 60 fps
                             step, god mode, test hooks)
tools/                       disc extraction, UDF names, SPURS job lifting, perf report + issue zip, mod installer
docs/NOTES.md                development log: every fix, why, and how it was measured

Everything SETUP.bat produces (game/, port/, deps/, .venv/, saves, logs) is in .gitignore. Never commit or share those: they are the game.

Troubleshooting

• "RPCS3 did not write EBOOT.elf": close any open RPCS3 window and run SETUP.bat again, or decrypt by hand: RPCS3 → Utilities → Decrypt PS3 Binaries → game\PS3_GAME\USRDIR\EBOOT.BIN. If RPCS3 itself complains, install the PS3 firmware in RPCS3 first (File → Install Firmware).
• "EBOOT.BIN is not the tested one": only the USA disc (BLUS-30443, version as on the disc) is supported. Other regions or updated EBOOTs need different patches.
• Build tools not found: install Visual Studio 2022 Build Tools with Desktop development with C++ and LLVM (winget install LLVM.LLVM), or set LLVM_DIR to an LLVM folder, then run BUILD.bat.
• The game window stays black / closes: look at the end of logs\last_run_err.txt.
• "needs AVX2" message box: this build was made on a PC with AVX2 and yours has none. Run BUILD.bat on this PC (it picks the right setting), or set DS_AVX2=0 before BUILD.bat on the other one.

Credits and license

• ps3recomp by Ned Heller / sp00nznet (MIT): the recompiler and runtime this port is built on.
• RPCS3: used to decrypt the EBOOT, and as the reference for how the PS3 behaves.
• The PC Remaster mod is by fromsoftserve.

This repo's own code and patches are under the MIT license (see LICENSE). Demon's Souls is © Sony Interactive Entertainment / FromSoftware. This project is not affiliated with or endorsed by them, and contains none of their files. Buy the game and dump your own disc.