https://github.com/ValveSoftware/halflife/issues/2458

Fix NPCs change yaw more slowly when game is running at higher FPS by SamVanheer

dlls/basemonster.h

@@ -104,6 +104,8 @@ class CBaseMonster : public CBaseToggle
 
 	Vector				m_HackedGunPos;	// HACK until we can query end of gun
 
+	float               m_flLastYawTime; // Fix for higher FPS NPC yaw speed
+
 // Scripted sequence Info
 	SCRIPTSTATE			m_scriptState;		// internal cinematic state
 	CCineMonster		*m_pCine;

dlls/monsters.cpp

@@ -110,6 +110,7 @@ TYPEDESCRIPTION	CBaseMonster::m_SaveData[] =
 	DEFINE_FIELD(CBaseMonster, m_flDistLook, FIELD_FLOAT),
 	DEFINE_FIELD(CBaseMonster, m_iTriggerCondition, FIELD_INTEGER),
 	DEFINE_FIELD(CBaseMonster, m_iszTriggerTarget, FIELD_STRING),
+	DEFINE_FIELD(CBaseMonster, m_flLastYawTime, FIELD_FLOAT),
 
 	DEFINE_FIELD(CBaseMonster, m_HackedGunPos, FIELD_VECTOR),
 
@@ -2557,7 +2558,15 @@ float CBaseMonster::ChangeYaw(int yawSpeed)
 	ideal = pev->ideal_yaw;
 	if (current != ideal)
 	{
-		speed = (float)yawSpeed * gpGlobals->frametime * 10;
+		//speed = (float)yawSpeed * gpGlobals->frametime * 10;
+		float delta = gpGlobals->time - m_flLastYawTime;
+
+		//Clamp delta like the engine does with frametime
+		if (delta > 0.25)
+			delta = 0.25;
+
+		speed = (float)yawSpeed * delta * 10;
+
 		move = ideal - current;
 
 		if (ideal > current)
@@ -2597,6 +2606,8 @@ float CBaseMonster::ChangeYaw(int yawSpeed)
 	else
 		move = 0;
 
+	m_flLastYawTime = gpGlobals->time;
+
 	return move;
 }