Disc speed: post-BIOS switch via entry_pc, XA guard for FMVs

Boot stays at authentic 1x. Speed switch fires once when the game's
entry_pc is first dispatched — safely after the BIOS disc init and
Sony/PlayStation logo sequences complete. Uses entry_pc exact-match
rather than text range to avoid false-triggering on the BIOS shell
(RAM 0x30000-0x5B000 overlaps the game text range).

XA guard in apply_speed(): reverts to 1x whenever xa_stream_active,
protecting FMV playback from speed-up regardless of disc_speed setting.

CDROM_MIN_DELAY floor of 500 cycles prevents instant mode from firing
IRQs faster than the interrupt handler can process them.

Tomba game.toml: disc_speed = "4x" (instant proved too aggressive
for early game disc reads; 4x safe with XA guard protecting FMVs).

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

runtime/include/cdrom.h

@@ -9,10 +9,12 @@ extern "C" {
 
 void cdrom_init(const char* cue_path);
 
-/* Set disc speed multiplier. divisor=0 → instant (all delays collapse to
- * 1 cycle, correct INT sequence fires as fast as host can process).
- * divisor=1 → authentic 1x. divisor=2 → 2x. Call before first cdrom_tick. */
+/* Set disc speed multiplier immediately. divisor=0 → instant, 1 → 1x, 2 → 2x. */
 void cdrom_set_speed(int divisor);
+/* Store configured game speed (applied post-BIOS via cdrom_notify_game_started). */
+void cdrom_set_game_speed(int divisor);
+/* Called by fntrace on first game-range dispatch; switches to game speed. */
+void cdrom_notify_game_started(void);
 
 /* MMIO read/write (0x1F801800-0x1F801803) */
 uint32_t cdrom_read(uint32_t addr);

runtime/include/fntrace.h

@@ -48,6 +48,9 @@ extern uint64_t     g_fntrace_seq;     /* monotonic; index into ring = seq % CAP
 
 /* Hot path. Called from psx_dispatch on every entry. Inlinable. */
 void fntrace_record(CPUState* cpu, uint32_t target);
+/* Register the game's text range for one-shot game-start detection.
+ * First dispatch into [lo, hi) calls cdrom_notify_game_started(). */
+void fntrace_set_game_range(uint32_t lo, uint32_t hi);
 
 /* Arm a target filter. arm_count == 0 means "record all" (default).
  * When arm_count > 0, only dispatches whose target matches one of the

runtime/src/cdrom.c

@@ -86,18 +86,40 @@ static uint8_t xa_stream_file;
 static uint8_t xa_stream_channel;
 static int xa_stream_active;
 
-/* 0 = instant (every delay collapses to 1 cycle), >0 = divisor applied to
- * all timing constants. Set via cdrom_set_speed() from main before first use. */
+/* Operating divisor: 1x during BIOS boot, switches to g_game_divisor
+ * when the game's entry point first fires (via cdrom_notify_game_started). */
 static int g_disc_speed_divisor = 1;
+/* Configured target speed — applied post-BIOS. */
+static int g_game_divisor = 1;
 
 void cdrom_set_speed(int divisor) {
     g_disc_speed_divisor = divisor;
 }
 
+/* Store the configured speed for post-BIOS application. Boot stays at 1x. */
+void cdrom_set_game_speed(int divisor) {
+    g_game_divisor = divisor;
+}
+
+/* Called by fntrace_record on first game-range dispatch. */
+void cdrom_notify_game_started(void) {
+    g_disc_speed_divisor = g_game_divisor;
+}
+
+/* Minimum cycles between CD-ROM IRQs in fast modes. Must be enough for the
+ * interrupt handler to save state, check the IRQ flag, process data, and
+ * return. Too low → interrupt fires before the previous one is processed →
+ * game hangs. 500 cycles ≈ 15µs at 33MHz, still ~900x faster than authentic. */
+#define CDROM_MIN_DELAY 500
+
 static int apply_speed(int delay) {
-    if (g_disc_speed_divisor == 0) return 1;
+    /* XA streaming (FMV / CDDA background music): preserve authentic timing.
+     * FMVs interleave XA audio + MDEC video — speeding up sector delivery
+     * would cause both to play faster than the display refresh rate. */
+    if (xa_stream_active) return delay;
+    if (g_disc_speed_divisor == 0) return CDROM_MIN_DELAY;
     int d = delay / g_disc_speed_divisor;
-    return d < 1 ? 1 : d;
+    return d < CDROM_MIN_DELAY ? CDROM_MIN_DELAY : d;
 }
 
 static int sector_delay_cycles(void) {

runtime/src/fntrace.c

@@ -13,6 +13,21 @@ static uint32_t s_arm_targets[FNTRACE_ARM_MAX];
 static uint32_t s_arm_count = 0;
 static uint32_t s_arm_record_all = 0;  /* opt-in via fntrace_arm(0xFFFFFFFF) */
 
+/* One-shot game-start detection: fire cdrom_notify_game_started() the first
+ * time the game's entry_pc is dispatched. Using entry_pc (not a range) avoids
+ * false-triggering on the BIOS shell, which runs from RAM 0x30000-0x5B000 —
+ * overlapping the game text range but never at entry_pc. */
+static uint32_t s_game_entry_phys = 0;
+static int      s_game_started = 0;
+extern void cdrom_notify_game_started(void);
+
+void fntrace_set_game_range(uint32_t lo, uint32_t hi) {
+    /* lo is treated as entry_pc; hi is ignored (kept for API compat). */
+    (void)hi;
+    s_game_entry_phys = lo & 0x1FFFFFFFu;
+    s_game_started = 0;
+}
+
 static inline int armed_match(uint32_t target) {
     if (s_arm_record_all) return 1;
     /* Hot path: when nothing is armed, record nothing. Recording every
@@ -27,6 +42,12 @@ static inline int armed_match(uint32_t target) {
 }
 
 void fntrace_record(CPUState* cpu, uint32_t target) {
+    if (!s_game_started && s_game_entry_phys != 0) {
+        if ((target & 0x1FFFFFFFu) == s_game_entry_phys) {
+            s_game_started = 1;
+            cdrom_notify_game_started();
+        }
+    }
     if (!armed_match(target)) return;
     uint64_t idx = g_fntrace_seq++ & (FNTRACE_RING_CAP - 1);
     FntraceEntry* e = &g_fntrace_ring[idx];

runtime/src/main.cpp

@@ -8,6 +8,7 @@
 #include "cpu_state.h"
 #include "psx_interpreter.h"
 #include "cdrom.h"
+#include "fntrace.h"
 #include "gpu.h"
 #include "sio.h"
 #include "spu.h"
@@ -1073,6 +1074,7 @@ int main(int argc, char** argv) {
     std::string game_name;
     std::string game_id;
     std::string disc_speed;   /* "1x" | "2x" | "4x" | "instant" */
+    uint32_t   game_entry_pc = 0;
 
     if (game_config_path) {
         try {
@@ -1084,6 +1086,7 @@ int main(int argc, char** argv) {
             if (gc.runtime.has_window_title) window_title  = gc.runtime.window_title;
             if (gc.runtime.has_debug_port)   debug_port    = gc.runtime.debug_port;
             if (gc.runtime.has_disc_speed)   disc_speed    = gc.runtime.disc_speed;
+            game_entry_pc = gc.entry_pc;
             std::fprintf(stdout, "psxrecomp: loaded game config %s (%s, %s)\n",
                          game_config_path, game_name.c_str(), game_id.c_str());
         } catch (const std::exception& ex) {
@@ -1130,10 +1133,12 @@ int main(int argc, char** argv) {
         if (disc_speed == "instant") divisor = 0;
         else if (disc_speed == "4x") divisor = 4;
         else if (disc_speed == "2x") divisor = 2;
+        /* Store for post-BIOS application; boot always runs at 1x so the
+         * BIOS disc-init sequence sees correct timing. */
+        cdrom_set_game_speed(divisor);
         if (divisor != 1)
-            std::fprintf(stdout, "psxrecomp: disc_speed=%s (divisor=%d)\n",
-                         disc_speed.c_str(), divisor);
-        cdrom_set_speed(divisor);
+            std::fprintf(stdout, "psxrecomp: disc_speed=%s (applied post-BIOS)\n",
+                         disc_speed.c_str());
     }
     memcard_init(memcard_dir_str.c_str());
     std::atexit(memcard_flush_all);
@@ -1144,6 +1149,10 @@ int main(int argc, char** argv) {
 #endif
     /* Heartbeat always on — see freeze_heartbeat.c rationale. */
     freeze_heartbeat_start("psx-runtime");
+    /* Register game entry_pc for post-BIOS disc speed switch. Fires once when
+     * the BIOS hands control to the game EXE — not on the BIOS shell. */
+    if (game_entry_pc != 0)
+        fntrace_set_game_range(game_entry_pc, 0);
 
     /* ---- SDL init ---- */
     SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "0");