diff --git a/config/rel_slices.yml b/config/rel_slices.yml
index 745039a7..35e58d8e 100644
--- a/config/rel_slices.yml
+++ b/config/rel_slices.yml
@@ -52,6 +52,10 @@ graph.c:
     .text: [0x80405518, 0x80405EC8]
     .data: [0x8065ECA8, 0x8065ECB0]
     .bss: [0x812F31E8, 0x812F3560]
+#irqmgr.c:
+#    .text: [0x80405EC8, 0x80406480]
+#    .data: [0x8065ECB0, 0x8065ECD0]
+#    .bss: [0x812F3560, 0x812F4CB0]
 lb_rtc.c:
     .text: [0x80406480, 0x8040752C]
     .rodata: [0x806436F8, 0x806437A0]
diff --git a/include/dolphin/os/OSTimer.h b/include/dolphin/os/OSTimer.h
index a45137ec..e1ec2433 100644
--- a/include/dolphin/os/OSTimer.h
+++ b/include/dolphin/os/OSTimer.h
@@ -5,6 +5,7 @@
 
 #include "types.h"
 #include "dolphin/os/OSAlarm.h"
+#include "dolphin/os/OSMessage.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/include/irqmgr.h b/include/irqmgr.h
index 92030758..d4ca499e 100644
--- a/include/irqmgr.h
+++ b/include/irqmgr.h
@@ -4,6 +4,7 @@
 #include "types.h"
 #include "dolphin/os/OSTime.h"
 #include "dolphin/os/OSTimer.h"
+#include "dolphin/os/OSMessage.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -31,16 +32,33 @@ typedef struct {
   irqmgr_mesg_t msgDelayPreNMI;
   OSMessageQueue _msgQueue;
   OSMessage _msgBuf[IRQMGR_MESSAGES_MAX];
-  OSThread thread;
-  irqmgr_client_t* clients;
-  u8 prenmi;
+
+  union {
+    OSThread thread;
+    struct {
+      u8 unused[sizeof(OSThread) - 2 * sizeof(void*)];
+      irqmgr_client_t* clients;
+      u8 prenmi;
+    };
+  };
+
   OSTime prenmi_time;
   OSTimer timer;
   OSTime retraceTime;
 } irqmgr_t;
 
+extern void irqmgr_AddClient(irqmgr_client_t* client, OSMessageQueue* msgqueue);
+/* @unused extern void irqmgr_RemoveClient(irqmgr_client_t* client) */
+extern void CreateIRQManager(void* stack, size_t stack_size, int priority, u8 retracecount);
+
+/* probably declared in os_vi.h */
+extern void osViSetEvent(OSMessageQueue* mesgq, OSMessage msg, u32 retcount);
+
 extern volatile int ResetStatus;
 extern volatile OSTime ResetTime;
+extern volatile OSTime RetraceTime;
+extern volatile int RetraceCount;
+extern irqmgr_t irqmgr_class;
 
 #ifdef __cplusplus
 };
diff --git a/include/libultra/os_thread.h b/include/libultra/os_thread.h
new file mode 100644
index 00000000..3c21805f
--- /dev/null
+++ b/include/libultra/os_thread.h
@@ -0,0 +1,18 @@
+#ifndef LIBULTRA_OS_THREAD_H
+#define LIBULTRA_OS_THREAD_H
+
+#include "types.h"
+#include "dolphin/os/OSThread.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+extern void osCreateThread2(OSThread* t, int id, void(*entry)(void*), void* arg, void* stack_pointer, size_t stack_size, OSPriority priority);
+extern void osStartThread(OSThread* t);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/rel/irqmgr.c b/rel/irqmgr.c
new file mode 100644
index 00000000..17785fc2
--- /dev/null
+++ b/rel/irqmgr.c
@@ -0,0 +1,217 @@
+#include "irqmgr.h"
+#include "libultra/os_thread.h"
+#include "dolphin/os.h"
+#include "dolphin/os/OSMessage.h"
+#include "dolphin/os/OSTime.h"
+
+#define MSEC(x) OSMicrosecondsToTicks((x) * (OSTime)1000)
+
+volatile int ResetStatus;             // 0x00
+volatile OSTime ResetTime;    // 0x08
+volatile OSTime RetraceTime;  // 0x10
+volatile int RetraceCount;    // 0x18
+static irqmgr_t* this;               // 0x1C
+irqmgr_t irqmgr_class;
+
+#define IRQ_RETRACE_MSG 666
+#define IRQ_PRENMI_MSG 669
+#define IRQ_PRENMI450_MSG 671
+#define IRQ_PRENMI480_MSG 672
+#define IRQ_PRENMI500_MSG 673
+
+/**
+ * @brief Adds anew client to the IRQ manager with a callback message queue.
+ * 
+ * @param client The new client to add
+ * @param msgqueue The callback message queue
+ **/
+extern void irqmgr_AddClient(irqmgr_client_t* client, OSMessageQueue* msgqueue) {
+  BOOL enable = OSDisableInterrupts();
+  client->msgQueue = msgqueue;
+  client->next = this->clients;
+  this->clients = client;
+  OSRestoreInterrupts(enable);
+
+  if (this->prenmi >= 1) {
+    osSendMesg(client->msgQueue, &this->msgPreNMI, 0);
+  }
+  if (this->prenmi >= 2) {
+    osSendMesg(client->msgQueue, &this->msgDelayPreNMI, 0);
+  }
+}
+
+/* @unused extern void irqmgr_RemoveClient(irqmgr_client_t* client) */
+
+/**
+ * @brief Sends a new message to all active IRQ clients.
+ * 
+ * @param msg The message which will be sent
+ **/
+static void irqmgr_SendMesgForClient(irqmgr_mesg_t* msg) {
+  irqmgr_client_t* i;
+  OSMessageQueue* mesgq;
+  for (i = this->clients; i != NULL; i = i->next) {
+    mesgq = i->msgQueue;
+    if (mesgq->usedCount < mesgq->msgCount) {
+      osSendMesg(mesgq, msg, 0);
+    }
+  }
+}
+
+/**
+ * @brief Sends a new message to all active IRQ clients. Duplicate of above.
+ * 
+ * @param msg The message which will be sent
+ **/
+static void irqmgr_JamMesgForClient(irqmgr_mesg_t* msg) {
+  irqmgr_client_t* i;
+  OSMessageQueue* mesgq;
+  for (i = this->clients; i != NULL; i = i->next) {
+    mesgq = i->msgQueue;
+    if (mesgq->usedCount < mesgq->msgCount) {
+      osSendMesg(mesgq, msg, 0);
+    }
+  }
+}
+
+#pragma pool_data on
+/**
+ * @brief Handler function for pre-NMI message.
+ **/
+static void irqmgr_HandlePreNMI() {
+  ResetStatus = 1;
+  this->prenmi = 1;
+  ResetTime = this->prenmi_time = osGetTime();
+
+  osSetTimer(&this->timer, MSEC(400), 0, &this->_msgQueue, (OSMessage)IRQ_PRENMI450_MSG);
+  irqmgr_JamMesgForClient(&this->msgPreNMI);
+}
+#pragma pool_data reset
+
+/**
+ * @brief Handler for pre-NMI message (post 400ms).
+ **/
+static void irqmgr_HandlePreNMI450() {
+  ResetStatus = 2;
+  this->prenmi = 2;
+  osSetTimer(&this->timer, MSEC(50), 0, &this->_msgQueue, (OSMessage)IRQ_PRENMI480_MSG);
+  irqmgr_SendMesgForClient(&this->msgDelayPreNMI);
+}
+
+/**
+ * @brief Handler for pre-NMI message (post 450ms).
+ **/
+static void irqmgr_HandlePreNMI480() {
+  osSetTimer(&this->timer, MSEC(50), 0, &this->_msgQueue, (OSMessage)IRQ_PRENMI500_MSG);
+}
+
+/**
+ * @brief Handler for pre-NMI message (post 500ms).
+ **/
+static void irqmgr_HandlePreNMI500() {}
+
+#pragma pool_data on
+/**
+ * @brief Handler for retrace message.
+ **/
+static void irqmgr_HandleRetrace() {
+  OSTime time;
+  if (RetraceTime == 0) {
+    if (this->retraceTime == 0) {
+      time = osGetTime();
+      this->retraceTime = time;
+    }
+    else {
+      time = osGetTime();
+      RetraceTime = time - this->retraceTime;
+    }
+  }
+  RetraceCount++;
+  irqmgr_SendMesgForClient(&this->msgRetrace);
+}
+#pragma pool_data reset
+
+/**
+ * @brief Main IRQ manager handler.
+ * 
+ * @param arg unused OSThread func arg
+ **/
+static void irqmgr_Main(void* arg) {
+  OSMessage msg = (OSMessage)0;
+
+  while (TRUE) {
+    osRecvMesg(&this->_msgQueue, &msg, 1);
+    switch ((u32)msg) {
+      case IRQ_RETRACE_MSG:
+        irqmgr_HandleRetrace();
+        break;
+      case IRQ_PRENMI_MSG:
+        irqmgr_HandlePreNMI();
+        break;
+      case IRQ_PRENMI450_MSG:
+        irqmgr_HandlePreNMI450();
+        break;
+      case IRQ_PRENMI480_MSG:
+        irqmgr_HandlePreNMI480();
+        break;
+      case IRQ_PRENMI500_MSG:
+        irqmgr_HandlePreNMI500();
+        break;
+      default:
+        break;
+    }
+  }
+}
+
+/**
+ * @brief Creates a new IRQ manager.
+ * 
+ * @param stack The IRQ manager's stack
+ * @param stack_size The IRQ manager's stack size
+ * @param priority The thread's priority
+ * @param retracecount Taken by osViSetEvent, unused
+ **/
+extern void CreateIRQManager(void* stack, size_t stack_size, int priority, u8 retracecount) {
+  this = &irqmgr_class;
+  this->clients = NULL;
+  this->msgRetrace.type = 1;
+  this->msgPreNMI.type = 4;
+  this->msgDelayPreNMI.type = 3;
+  this->prenmi = 0;
+  this->prenmi_time = 0;
+
+  osCreateMesgQueue(&this->_msgQueue, this->_msgBuf, 8);
+  osViSetEvent(&this->_msgQueue, (OSMessage)IRQ_RETRACE_MSG, retracecount);
+  osCreateThread2(&this->thread, 9, irqmgr_Main, NULL, stack, stack_size, priority);
+  osStartThread(&this->thread);
+}
+
+/* these were probably written in a header directly and included here */
+
+#define VI_STACK_SIZE 0x1000
+
+static OSMessage vc_msg;
+static OSMessageQueue* vc_msgq;
+static u16 vc_retraceCount;
+static u16 retrace; /* this probably belongs in one of the unused vi functions below */
+static u8 viThreadStack[VI_STACK_SIZE];
+static OSThread viThread;
+
+/* @unused ? viMgrMain(?) */
+
+/* @unused ? osCreateViManager(?) */
+
+#pragma pool_data on
+/**
+ * @brief Sets the VI event info. Stubbed outside this functionality.
+ * 
+ * @param msgq The OSMessageQueue which would be notified upon event invocation
+ * @param msg The OSMessage which would be sent upon event invocation
+ * @param retcount The retrace count before invoking the event
+ **/
+extern void osViSetEvent(OSMessageQueue* mesgq, OSMessage msg, u32 retcount) {
+  vc_msgq = mesgq;
+  vc_msg = msg;
+  vc_retraceCount = retcount;
+}
+#pragma pool_data reset