Proper CPU reset.

DotN64/CPU/CP0/VR4300.SystemControlUnit.ConfigRegister.cs

@@ -7,6 +7,9 @@ namespace DotN64.CPU
     {
         public partial class SystemControlUnit
         {
+            /// <summary>
+            /// See: datasheet#5.4.6.
+            /// </summary>
             public class ConfigRegister : Register
             {
                 #region Fields

DotN64/CPU/CP0/VR4300.SystemControlUnit.StatusRegister.cs

@@ -7,6 +7,9 @@ namespace DotN64.CPU
     {
         public partial class SystemControlUnit
         {
+            /// <summary>
+            /// See: datasheet#6.3.5.
+            /// </summary>
             public class StatusRegister : Register
             {
                 #region Fields

DotN64/CPU/CP0/VR4300.SystemControlUnit.cs

@@ -31,15 +31,6 @@ namespace DotN64.CPU
             #endregion
 
             #region Methods
-            /// <summary>
-            /// Cold reset.
-            /// </summary>
-            public void Reset()
-            {
-                Config.EP = ConfigRegister.TransferDataPattern.D;
-                Config.BE = ConfigRegister.Endianness.BigEndian;
-            }
-
             /// <summary>
             /// Translates a virtual address into a physical address.
             /// See: datasheet#5.2.4 Table 5-3.

DotN64/CPU/VR4300.cs

@@ -3,7 +3,10 @@ using System.Collections.Generic;
 
 namespace DotN64.CPU
 {
-    // Reference: http://datasheets.chipdb.org/NEC/Vr-Series/Vr43xx/U10504EJ7V0UMJ1.pdf
+    /// <summary>
+    /// The NEC VR4300 CPU, designed by MIPS Technologies.
+    /// Datasheet: http://datasheets.chipdb.org/NEC/Vr-Series/Vr43xx/U10504EJ7V0UMJ1.pdf
+    /// </summary>
     public partial class VR4300
     {
         #region Fields
@@ -12,6 +15,8 @@ namespace DotN64.CPU
         private readonly IReadOnlyDictionary<RegImmOpCode, Action<Instruction>> regImmOperations;
         private ulong? delaySlot;
 
+        private const ulong ResetVector = 0xFFFFFFFFBFC00000;
+
         private delegate bool BranchCondition(ulong rs, ulong rt);
         #endregion
 
@@ -57,6 +62,17 @@ namespace DotN64.CPU
         public float FCR31 { get; set; }
 
         public SystemControlUnit CP0 { get; }
+
+        private byte divMode;
+        /// <summary>
+        /// Internal operating frequency mode.
+        /// See: datasheet#2.2.2 Table 2-2.
+        /// </summary>
+        public byte DivMode
+        {
+            get => divMode;
+            set => divMode = (byte)(value & ((1 << 2) - 1));
+        }
         #endregion
 
         #region Constructors
@@ -130,12 +146,25 @@ namespace DotN64.CPU
         #region Methods
         /// <summary>
         /// Cold reset.
+        /// See: datasheet#6.4.4.
         /// </summary>
         public void Reset()
         {
-            PC = 0xFFFFFFFFBFC00000;
+            PC = ResetVector;
 
-            CP0.Reset();
+            var ds = CP0.Status.DS;
+
+            ds.TS = ds.SR = CP0.Status.RP = false;
+            CP0.Config.EP = 0;
+
+            CP0.Status.ERL = ds.BEV = true;
+            CP0.Config.BE = (SystemControlUnit.ConfigRegister.Endianness)1;
+
+            CP0.Registers[(int)SystemControlUnit.RegisterIndex.Random] = 31;
+
+            CP0.Config.EC = DivMode;
+
+            CP0.Status.DS = ds;
         }
 
         public void Run(Instruction instruction)

DotN64/Nintendo64.cs

@@ -99,15 +99,15 @@ namespace DotN64
                     Write = RI.WriteWord
                 }
             };
-            CPU = new VR4300(memoryMaps);
+            CPU = new VR4300(memoryMaps)
+            {
+                DivMode = 0b01 // Assuming this value as the CPU is clocked at 93.75 MHz, and the RCP would be clocked at 93.75 / 3 * 2 = 62.5 MHz.
+            };
         }
         #endregion
 
         #region Methods
-        /// <summary>
-        /// Emulates the PIF ROM.
-        /// </summary>
-        private void RunPIF()
+        private void EmulatePIFBootROM()
         {
             // Replicating the memory writes to properly initialise the subsystems.
             var writes = new uint[,]
@@ -171,7 +171,7 @@ namespace DotN64
             CPU.Reset();
 
             if (PI.BootROM == null)
-                RunPIF();
+                EmulatePIFBootROM();
 
             while (true)
             {