Turns out the 'performance problem' is just me setting the framerate. Weird thing though is setting that also changes how SFML updates the textures when doing texture.update(). Need to investigate why.

Makefile

@@ -15,13 +15,13 @@ debug_build:
 	meson compile -j 4 -C builddir
 
 run: build
-	./builddir/b8rk.exe 1 1 ./roms/test_opcode.ch8
+	./builddir/b8rk.exe 1 1 ./roms/tetris.ch8
 
 debug: build
 	gdb --nx -x .gdbinit --ex run --args builddir/runtests.exe
 
 debug_run: build
-	gdb --nx -x .gdbinit --batch --ex run --ex bt --ex q --args builddir/b8rk.exe 1 1 ./roms/test_opcode.ch8
+	gdb --nx -x .gdbinit --batch --ex run --ex bt --ex q --args builddir/b8rk.exe 1 1 ./roms/tetris.ch8
 
 clean:
 	meson compile --clean -C builddir

src/main.cpp

@@ -56,7 +56,7 @@ struct Display {
 
   void update(Chip8& vm) {
     handle_inputs(vm);
-    texture.update((uint8_t *)(vm.video));
+    texture.update((uint8_t *)(vm.video), {64, 32}, {0,0});
   }
 
   void render() {
@@ -70,7 +70,6 @@ struct Display {
   }
 };
 
-
 int main(int argc, char* argv[]) {
   if(argc != 4) {
     fmt::print("ERROR!");
@@ -78,18 +77,17 @@ int main(int argc, char* argv[]) {
   }
 
   int videoScale = std::stoi(argv[1]);
-  int cycleDelay = std::stoi(argv[2]);
+  int framerate = std::stoi(argv[2]);
   std::string romFilename{argv[3]};
 
   Chip8 chip8;
   chip8.LoadROM(romFilename);
 
   int videoPitch = sizeof(chip8.video[0]) * VIDEO_WIDTH;
-  auto lastCycleTime = std::chrono::high_resolution_clock::now();
 
   sf::RenderWindow window{sf::VideoMode({1280, 720}), "Chip8 Emulator"};
-  window.setFramerateLimit(60);
+  window.setFramerateLimit(framerate);
-  window.setVerticalSyncEnabled(true);
+  window.setVerticalSyncEnabled(false);
 
   Display display{window, {0, 0}, {1000, 1000}};
   Stats cycle_stats;
@@ -97,16 +95,9 @@ int main(int argc, char* argv[]) {
   Stats update_stats;
 
   while (display.active()) {
-    auto currentTime = std::chrono::high_resolution_clock::now();
+    auto t = cycle_stats.time_start();
-    float dt = std::chrono::duration<float, std::chrono::milliseconds::period>(currentTime - lastCycleTime).count();
+    chip8.Cycle();
-
+    cycle_stats.sample_time(t);
-    if (dt > cycleDelay)
-    {
-        lastCycleTime = currentTime;
-        auto t = cycle_stats.time_start();
-        chip8.Cycle();
-        cycle_stats.sample_time(t);
-    }
 
     auto ut = update_stats.time_start();
     display.update(chip8);