diff --git a/Source/Core/Core/HW/SystemTimers.cpp b/Source/Core/Core/HW/SystemTimers.cpp
@@ -100,7 +100,7 @@ std::mutex s_emu_to_real_time_mutex;
 u64 s_time_spent_sleeping;
 
 // DSP/CPU timeslicing.
-void DSPCallback(u64 userdata, s64 cyclesLate)
+void DSPCallback(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   // splits up the cycle budget in case lle is used
   // for hle, just gives all of the slice to hle
@@ -115,13 +115,13 @@ int GetAudioDMACallbackPeriod()
          (Mixer::FIXED_SAMPLE_RATE_DIVIDEND * 4 / 32);
 }
 
-void AudioDMACallback(u64 userdata, s64 cyclesLate)
+void AudioDMACallback(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   DSP::UpdateAudioDMA();  // Push audio to speakers.
   CoreTiming::ScheduleEvent(GetAudioDMACallbackPeriod() - cyclesLate, et_AudioDMA);
 }
 
-void IPC_HLE_UpdateCallback(u64 userdata, s64 cyclesLate)
+void IPC_HLE_UpdateCallback(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   if (SConfig::GetInstance().bWii)
   {
@@ -130,19 +130,19 @@ void IPC_HLE_UpdateCallback(u64 userdata, s64 cyclesLate)
   }
 }
 
-void VICallback(u64 userdata, s64 cyclesLate)
+void VICallback(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   VideoInterface::Update(CoreTiming::GetTicks() - cyclesLate);
   CoreTiming::ScheduleEvent(VideoInterface::GetTicksPerHalfLine() - cyclesLate, et_VI);
 }
 
-void DecrementerCallback(u64 userdata, s64 cyclesLate)
+void DecrementerCallback(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   PowerPC::ppcState.spr[SPR_DEC] = 0xFFFFFFFF;
   PowerPC::ppcState.Exceptions |= EXCEPTION_DECREMENTER;
 }
 
-void PatchEngineCallback(u64 userdata, s64 cycles_late)
+void PatchEngineCallback(Core::System& system, u64 userdata, s64 cycles_late)
 {
   // We have 2 periods, a 1000 cycle error period and the VI period.
   // We have to carefully combine these together so that we stay on the VI period without drifting.
@@ -167,7 +167,7 @@ void PatchEngineCallback(u64 userdata, s64 cycles_late)
   CoreTiming::ScheduleEvent(next_schedule, et_PatchEngine, cycles_pruned);
 }
 
-void ThrottleCallback(u64 deadline, s64 cyclesLate)
+void ThrottleCallback(Core::System& system, u64 deadline, s64 cyclesLate)
 {
   // Allow the GPU thread to sleep. Setting this flag here limits the wakeups to 1 kHz.
   Fifo::GpuMaySleep();

diff --git a/Source/Core/Core/HW/WII_IPC.cpp b/Source/Core/Core/HW/WII_IPC.cpp
@@ -112,7 +112,7 @@ Common::Flags<GPIO> g_gpio_out;
 static u32 resets;
 
 static CoreTiming::EventType* updateInterrupts;
-static void UpdateInterrupts(u64 = 0, s64 cyclesLate = 0);
+static void UpdateInterrupts(Core::System& system, u64 userdata, s64 cyclesLate);
 
 void DoState(PointerWrap& p)
 {
@@ -283,7 +283,7 @@ void RegisterMMIO(MMIO::Mapping* mmio, u32 base)
   mmio->Register(base | UNK_1D0, MMIO::Constant<u32>(0), MMIO::Nop<u32>());
 }
 
-static void UpdateInterrupts(u64 userdata, s64 cyclesLate)
+static void UpdateInterrupts(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   if ((ctrl.Y1 & ctrl.IY1) || (ctrl.Y2 & ctrl.IY2))
   {

diff --git a/Source/Core/Core/IOS/DI/DI.cpp b/Source/Core/Core/IOS/DI/DI.cpp
@@ -624,7 +624,7 @@ void DIDevice::InterruptFromDVDInterface(DVDInterface::DIInterruptType interrupt
   }
 }
 
-void DIDevice::FinishDICommandCallback(u64 userdata, s64 ticksbehind)
+void DIDevice::FinishDICommandCallback(Core::System& system, u64 userdata, s64 ticksbehind)
 {
   const DIResult result = static_cast<DIResult>(userdata);
 

diff --git a/Source/Core/Core/IOS/DI/DI.h b/Source/Core/Core/IOS/DI/DI.h
@@ -19,6 +19,10 @@ namespace DVDInterface
 {
 enum class DIInterruptType : int;
 }
+namespace Core
+{
+class System;
+}
 namespace CoreTiming
 {
 struct EventType;
@@ -128,7 +132,7 @@ class DIDevice : public Device
   void ChangePartition(const DiscIO::Partition partition);
   void InitializeIfFirstTime();
   void ResetDIRegisters();
-  static void FinishDICommandCallback(u64 userdata, s64 ticksbehind);
+  static void FinishDICommandCallback(Core::System& system, u64 userdata, s64 ticksbehind);
   void FinishDICommand(DIResult result);
 
   static CoreTiming::EventType* s_finish_executing_di_command;

diff --git a/Source/Core/Core/IOS/ES/ES.cpp b/Source/Core/Core/IOS/ES/ES.cpp
@@ -115,13 +115,15 @@ ESDevice::ESDevice(Kernel& ios, const std::string& device_name) : Device(ios, de
 void ESDevice::InitializeEmulationState()
 {
   s_finish_init_event = CoreTiming::RegisterEvent(
-      "IOS-ESFinishInit", [](u64, s64) { GetIOS()->GetES()->FinishInit(); });
-  s_reload_ios_for_ppc_launch_event =
-      CoreTiming::RegisterEvent("IOS-ESReloadIOSForPPCLaunch", [](u64 ios_id, s64) {
+      "IOS-ESFinishInit", [](Core::System& system, u64, s64) { GetIOS()->GetES()->FinishInit(); });
+  s_reload_ios_for_ppc_launch_event = CoreTiming::RegisterEvent(
+      "IOS-ESReloadIOSForPPCLaunch", [](Core::System& system, u64 ios_id, s64) {
         GetIOS()->GetES()->LaunchTitle(ios_id, HangPPC::Yes);
       });
-  s_bootstrap_ppc_for_launch_event = CoreTiming::RegisterEvent(
-      "IOS-ESBootstrapPPCForLaunch", [](u64, s64) { GetIOS()->GetES()->BootstrapPPC(); });
+  s_bootstrap_ppc_for_launch_event =
+      CoreTiming::RegisterEvent("IOS-ESBootstrapPPCForLaunch", [](Core::System& system, u64, s64) {
+        GetIOS()->GetES()->BootstrapPPC();
+      });
 }
 
 void ESDevice::FinalizeEmulationState()

diff --git a/Source/Core/Core/IOS/IOS.cpp b/Source/Core/Core/IOS/IOS.cpp
@@ -876,7 +876,7 @@ IOSC& Kernel::GetIOSC()
   return m_iosc;
 }
 
-static void FinishPPCBootstrap(u64 userdata, s64 cycles_late)
+static void FinishPPCBootstrap(Core::System& system, u64 userdata, s64 cycles_late)
 {
   // See Kernel::BootstrapPPC
   const bool is_ancast = userdata == 1;
@@ -891,18 +891,20 @@ static void FinishPPCBootstrap(u64 userdata, s64 cycles_late)
 
 void Init()
 {
-  s_event_enqueue = CoreTiming::RegisterEvent("IPCEvent", [](u64 userdata, s64) {
-    if (s_ios)
-      s_ios->HandleIPCEvent(userdata);
-  });
+  s_event_enqueue =
+      CoreTiming::RegisterEvent("IPCEvent", [](Core::System& system, u64 userdata, s64) {
+        if (s_ios)
+          s_ios->HandleIPCEvent(userdata);
+      });
 
   ESDevice::InitializeEmulationState();
 
   s_event_finish_ppc_bootstrap =
       CoreTiming::RegisterEvent("IOSFinishPPCBootstrap", FinishPPCBootstrap);
 
-  s_event_finish_ios_boot = CoreTiming::RegisterEvent(
-      "IOSFinishIOSBoot", [](u64 ios_title_id, s64) { FinishIOSBoot(ios_title_id); });
+  s_event_finish_ios_boot =
+      CoreTiming::RegisterEvent("IOSFinishIOSBoot", [](Core::System& system, u64 ios_title_id,
+                                                       s64) { FinishIOSBoot(ios_title_id); });
 
   DIDevice::s_finish_executing_di_command =
       CoreTiming::RegisterEvent("FinishDICommand", DIDevice::FinishDICommandCallback);

diff --git a/Source/Core/Core/PowerPC/GDBStub.cpp b/Source/Core/Core/PowerPC/GDBStub.cpp
@@ -124,7 +124,7 @@ static void Hex2mem(u8* dst, u8* src, u32 len)
   }
 }
 
-static void UpdateCallback(u64 userdata, s64 cycles_late)
+static void UpdateCallback(Core::System& system, u64 userdata, s64 cycles_late)
 {
   ProcessCommands(false);
   if (IsActive())

diff --git a/Source/Core/Core/PowerPC/PowerPC.cpp b/Source/Core/Core/PowerPC/PowerPC.cpp
@@ -68,7 +68,7 @@ void PairedSingle::SetPS1(double value)
   ps1 = Common::BitCast<u64>(value);
 }
 
-static void InvalidateCacheThreadSafe(u64 userdata, s64 cyclesLate)
+static void InvalidateCacheThreadSafe(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   ppcState.iCache.Invalidate(static_cast<u32>(userdata));
 }

diff --git a/Source/Core/VideoCommon/CommandProcessor.cpp b/Source/Core/VideoCommon/CommandProcessor.cpp
@@ -49,7 +49,7 @@ static bool IsOnThread()
   return Core::System::GetInstance().IsDualCoreMode();
 }
 
-static void UpdateInterrupts_Wrapper(u64 userdata, s64 cyclesLate)
+static void UpdateInterrupts_Wrapper(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   UpdateInterrupts(userdata);
 }

diff --git a/Source/Core/VideoCommon/Fifo.cpp b/Source/Core/VideoCommon/Fifo.cpp
@@ -595,12 +595,12 @@ static int WaitForGpuThread(int ticks)
   return GPU_TIME_SLOT_SIZE;
 }
 
-static void SyncGPUCallback(u64 ticks, s64 cyclesLate)
+static void SyncGPUCallback(Core::System& system, u64 ticks, s64 cyclesLate)
 {
   ticks += cyclesLate;
   int next = -1;
 
-  if (!Core::System::GetInstance().IsDualCoreMode() || s_use_deterministic_gpu_thread)
+  if (!system.IsDualCoreMode() || s_use_deterministic_gpu_thread)
   {
     next = RunGpuOnCpu((int)ticks);
   }

diff --git a/Source/Core/VideoCommon/PixelEngine.cpp b/Source/Core/VideoCommon/PixelEngine.cpp
@@ -182,7 +182,7 @@ void DoState(PointerWrap& p)
 }
 
 static void UpdateInterrupts();
-static void SetTokenFinish_OnMainThread(u64 userdata, s64 cyclesLate);
+static void SetTokenFinish_OnMainThread(Core::System& system, u64 userdata, s64 cyclesLate);
 
 void Init()
 {
@@ -297,7 +297,7 @@ static void UpdateInterrupts()
                                    s_signal_finish_interrupt && m_Control.pe_finish_enable);
 }
 
-static void SetTokenFinish_OnMainThread(u64 userdata, s64 cyclesLate)
+static void SetTokenFinish_OnMainThread(Core::System& system, u64 userdata, s64 cyclesLate)
 {
   std::unique_lock<std::mutex> lk(s_token_finish_mutex);
   s_event_raised = false;

diff --git a/Source/UnitTests/Core/CoreTimingTest.cpp b/Source/UnitTests/Core/CoreTimingTest.cpp
@@ -25,7 +25,7 @@ static u64 s_expected_callback = 0;
 static s64 s_lateness = 0;
 
 template <unsigned int IDX>
-void CallbackTemplate(u64 userdata, s64 lateness)
+void CallbackTemplate(Core::System& system, u64 userdata, s64 lateness)
 {
   static_assert(IDX < CB_IDS.size(), "IDX out of range");
   s_callbacks_ran_flags.set(IDX);
@@ -121,7 +121,7 @@ namespace SharedSlotTest
 static unsigned int s_counter = 0;
 
 template <unsigned int ID>
-void FifoCallback(u64 userdata, s64 lateness)
+void FifoCallback(Core::System& system, u64 userdata, s64 lateness)
 {
   static_assert(ID < CB_IDS.size(), "ID out of range");
   s_callbacks_ran_flags.set(ID);
@@ -186,7 +186,7 @@ namespace ChainSchedulingTest
 {
 static int s_reschedules = 0;
 
-static void RescheduleCallback(u64 userdata, s64 lateness)
+static void RescheduleCallback(Core::System& system, u64 userdata, s64 lateness)
 {
   --s_reschedules;
   EXPECT_TRUE(s_reschedules >= 0);
@@ -241,7 +241,7 @@ namespace ScheduleIntoPastTest
 {
 static CoreTiming::EventType* s_cb_next = nullptr;
 
-static void ChainCallback(u64 userdata, s64 lateness)
+static void ChainCallback(Core::System& system, u64 userdata, s64 lateness)
 {
   EXPECT_EQ(CB_IDS[0] + 1, userdata);
   EXPECT_EQ(0, lateness);