# UNDF: UNDF-2026-000001144
--- a/Source/iop/IopBios.h
+++ b/Source/iop/IopBios.h
@@ -670,6 +670,7 @@ private:
 	IntrHandlerList m_intrHandlers;
 	VblankHandlerList m_vblankHandlers;
+	std::array<int32, Iop::CIntc::LINES_MAX> m_intrHandlerIndex;

--- a/Source/iop/IopBios.cpp
+++ b/Source/iop/IopBios.cpp
@@ -159,6 +159,7 @@ void CIopBios::Reset(const BiosDebugInfoProviderPtr& debugInfoProvider)
 	m_intrHandlers.FreeAll();
+	m_intrHandlerIndex.fill(-1);
 	m_vblankHandlers.FreeAll();

@@ -3054,6 +3054,7 @@ int32 CIopBios::RegisterIntrHandler(uint32 line, uint32 mode, uint32 handler, uint32 arg)
 	assert(FindIntrHandler(line) == -1);
 	if(FindIntrHandler(line) != -1)
 	{
 		return KERNEL_RESULT_ERROR_FOUND_HANDLER;
 	}

 	if(line >= Iop::CIntc::LINES_MAX)
 	{
 		return KERNEL_RESULT_ERROR_ILLEGAL_INTRCODE;
 	}

 	//Registering a null handler is a no-op
 	if(handler == 0)
 	{
 		return KERNEL_RESULT_OK;
 	}

 	uint32 handlerId = m_intrHandlers.Allocate();
 	assert(handlerId != -1);
 	if(handlerId == -1)
 	{
 		return KERNEL_RESULT_ERROR;
 	}

 	auto intrHandler = m_intrHandlers[handlerId];
 	intrHandler->line = line;
 	intrHandler->mode = mode;
 	intrHandler->handler = handler;
 	intrHandler->arg = arg;
+	m_intrHandlerIndex[line] = static_cast<int32>(handlerId);

 	return KERNEL_RESULT_OK;
 }

@@ -3089,6 +3089,7 @@ int32 CIopBios::ReleaseIntrHandler(uint32 line)
 	uint32 handlerId = FindIntrHandler(line);
 	if(handlerId == -1)
 	{
 		return KERNEL_RESULT_ERROR_NOTFOUND_HANDLER;
 	}

 	m_intrHandlers.Free(handlerId);
+	m_intrHandlerIndex[line] = -1;
 	return KERNEL_RESULT_OK;
 }

@@ -3106,11 +3106,7 @@ int32 CIopBios::FindIntrHandler(uint32 line)
-{
-	for(auto handlerIterator = std::begin(m_intrHandlers); handlerIterator != std::end(m_intrHandlers); handlerIterator++)
-	{
-		auto handler = m_intrHandlers[handlerIterator];
-		if(!handler) continue;
-		if(handler->line == line) return handlerIterator;
-	}
-	return -1;
-}
+{
+	if(line >= Iop::CIntc::LINES_MAX) return -1;
+	return m_intrHandlerIndex[line];
+}