diff --git a/include/reactos/libs/fast486/fast486.h b/include/reactos/libs/fast486/fast486.h
index 4087a94cc29..5f6f27f36b4 100644
--- a/include/reactos/libs/fast486/fast486.h
+++ b/include/reactos/libs/fast486/fast486.h
@@ -185,7 +185,8 @@ VOID
     PFAST486_STATE State,
     ULONG Port,
     PVOID Buffer,
-    ULONG Size
+    ULONG Size,
+    UCHAR Width
 );
 
 typedef
@@ -195,7 +196,8 @@ VOID
     PFAST486_STATE State,
     ULONG Port,
     PVOID Buffer,
-    ULONG Size
+    ULONG Size,
+    UCHAR Width
 );
 
 typedef
diff --git a/lib/fast486/fast486.c b/lib/fast486/fast486.c
index 00cf7d8f495..e420ea1c446 100644
--- a/lib/fast486/fast486.c
+++ b/lib/fast486/fast486.c
@@ -146,22 +146,24 @@ Fast486MemWriteCallback(PFAST486_STATE State, ULONG Address, PVOID Buffer, ULONG
 
 static VOID
 NTAPI
-Fast486IoReadCallback(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size)
+Fast486IoReadCallback(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size, UCHAR Width)
 {
     UNREFERENCED_PARAMETER(State);
     UNREFERENCED_PARAMETER(Port);
     UNREFERENCED_PARAMETER(Buffer);
     UNREFERENCED_PARAMETER(Size);
+    UNREFERENCED_PARAMETER(Width);
 }
 
 static VOID
 NTAPI
-Fast486IoWriteCallback(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size)
+Fast486IoWriteCallback(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size, UCHAR Width)
 {
     UNREFERENCED_PARAMETER(State);
     UNREFERENCED_PARAMETER(Port);
     UNREFERENCED_PARAMETER(Buffer);
     UNREFERENCED_PARAMETER(Size);
+    UNREFERENCED_PARAMETER(Width);
 }
 
 static VOID
diff --git a/lib/fast486/opcodes.c b/lib/fast486/opcodes.c
index b5b032f2625..c61de2baf72 100644
--- a/lib/fast486/opcodes.c
+++ b/lib/fast486/opcodes.c
@@ -906,7 +906,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeInByte)
     }
 
     /* Read a byte from the I/O port */
-    State->IoReadCallback(State, Port, &Data, sizeof(UCHAR));
+    State->IoReadCallback(State, Port, &Data, 1, sizeof(UCHAR));
 
     /* Store the result in AL */
     State->GeneralRegs[FAST486_REG_EAX].LowByte = Data;
@@ -950,7 +950,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeIn)
         ULONG Data;
 
         /* Read a dword from the I/O port */
-        State->IoReadCallback(State, Port, &Data, sizeof(ULONG));
+        State->IoReadCallback(State, Port, &Data, 1, sizeof(ULONG));
 
         /* Store the value in EAX */
         State->GeneralRegs[FAST486_REG_EAX].Long = Data;
@@ -960,7 +960,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeIn)
         USHORT Data;
 
         /* Read a word from the I/O port */
-        State->IoReadCallback(State, Port, &Data, sizeof(USHORT));
+        State->IoReadCallback(State, Port, &Data, 1, sizeof(USHORT));
 
         /* Store the value in AX */
         State->GeneralRegs[FAST486_REG_EAX].LowWord = Data;
@@ -999,7 +999,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeOutByte)
     Data = State->GeneralRegs[FAST486_REG_EAX].LowByte;
     
     /* Write the byte to the I/O port */
-    State->IoWriteCallback(State, Port, &Data, sizeof(UCHAR));
+    State->IoWriteCallback(State, Port, &Data, 1, sizeof(UCHAR));
 
     return TRUE;
 }
@@ -1041,7 +1041,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeOut)
         ULONG Data = State->GeneralRegs[FAST486_REG_EAX].Long;
 
         /* Write a dword to the I/O port */
-        State->IoReadCallback(State, Port, &Data, sizeof(ULONG));
+        State->IoReadCallback(State, Port, &Data, 1, sizeof(ULONG));
     }
     else
     {
@@ -1049,7 +1049,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeOut)
         USHORT Data = State->GeneralRegs[FAST486_REG_EAX].LowWord;
 
         /* Write a word to the I/O port */
-        State->IoWriteCallback(State, Port, &Data, sizeof(USHORT));
+        State->IoWriteCallback(State, Port, &Data, 1, sizeof(USHORT));
     }
 
     return TRUE;
@@ -5997,7 +5997,8 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeIns)
             State->IoReadCallback(State,
                                   State->GeneralRegs[FAST486_REG_EDX].LowWord,
                                   Block,
-                                  Processed * DataSize);
+                                  Processed,
+                                  DataSize);
 
             if (State->Flags.Df)
             {
@@ -6059,6 +6060,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeIns)
         State->IoReadCallback(State,
                               State->GeneralRegs[FAST486_REG_EDX].LowWord,
                               &Data,
+                              1,
                               DataSize);
 
         /* Write to the destination operand */
@@ -6174,7 +6176,8 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeOuts)
             State->IoWriteCallback(State,
                                    State->GeneralRegs[FAST486_REG_EDX].LowWord,
                                    Block,
-                                   Processed * DataSize);
+                                   Processed,
+                                   DataSize);
 
             if (!State->Flags.Df)
             {
@@ -6212,6 +6215,7 @@ FAST486_OPCODE_HANDLER(Fast486OpcodeOuts)
         State->IoWriteCallback(State,
                                State->GeneralRegs[FAST486_REG_EDX].LowWord,
                                &Data,
+                               1,
                                DataSize);
 
         /* Increment/decrement ESI */
diff --git a/subsystems/ntvdm/emulator.c b/subsystems/ntvdm/emulator.c
index d9a24f8e872..501026cc5e4 100644
--- a/subsystems/ntvdm/emulator.c
+++ b/subsystems/ntvdm/emulator.c
@@ -82,28 +82,30 @@ static VOID WINAPI EmulatorWriteMemory(PFAST486_STATE State, ULONG Address, PVOI
     }
 }
 
-static VOID WINAPI EmulatorReadIo(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size)
+static VOID WINAPI EmulatorReadIo(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size, UCHAR Width)
 {
-    INT i;
+    INT i, j;
     LPBYTE Address = (LPBYTE)Buffer;
 
     UNREFERENCED_PARAMETER(State);
 
-    for (i = 0; i < Size; i++)
+    for (i = 0; i < Size; i++) for (j = 0; j < Width; j++)
     {
-        switch (Port)
+        ULONG CurrentPort = Port + j;
+
+        switch (CurrentPort)
         {
             case PIC_MASTER_CMD:
             case PIC_SLAVE_CMD:
             {
-                *(Address++) = PicReadCommand(Port);
+                *(Address++) = PicReadCommand(CurrentPort);
                 break;
             }
 
             case PIC_MASTER_DATA:
             case PIC_SLAVE_DATA:
             {
-                *(Address++) = PicReadData(Port);
+                *(Address++) = PicReadData(CurrentPort);
                 break;
             }
 
@@ -111,7 +113,7 @@ static VOID WINAPI EmulatorReadIo(PFAST486_STATE State, ULONG Port, PVOID Buffer
             case PIT_DATA_PORT(1):
             case PIT_DATA_PORT(2):
             {
-                *(Address++) = PitReadData(Port - PIT_DATA_PORT(0));
+                *(Address++) = PitReadData(CurrentPort - PIT_DATA_PORT(0));
                 break;
             }
 
@@ -155,28 +157,30 @@ static VOID WINAPI EmulatorReadIo(PFAST486_STATE State, ULONG Port, PVOID Buffer
             case VGA_STAT_MONO:
             case VGA_STAT_COLOR:
             {
-                *(Address++) = VgaReadPort(Port);
+                *(Address++) = VgaReadPort(CurrentPort);
                 break;
             }
 
             default:
             {
-                DPRINT1("Read from unknown port: 0x%X\n", Port);
+                DPRINT1("Read from unknown port: 0x%X\n", CurrentPort);
             }
         }
     }
 }
 
-static VOID WINAPI EmulatorWriteIo(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size)
+static VOID WINAPI EmulatorWriteIo(PFAST486_STATE State, ULONG Port, PVOID Buffer, ULONG Size, UCHAR Width)
 {
-    INT i;
+    INT i, j;
     LPBYTE Address = (LPBYTE)Buffer;
 
     UNREFERENCED_PARAMETER(State);
 
-    for (i = 0; i < Size; i++)
+    for (i = 0; i < Size; i++) for (j = 0; j < Width; j++)
     {
-        switch (Port)
+        ULONG CurrentPort = Port + j;
+
+        switch (CurrentPort)
         {
             case PIT_COMMAND_PORT:
             {
@@ -188,21 +192,21 @@ static VOID WINAPI EmulatorWriteIo(PFAST486_STATE State, ULONG Port, PVOID Buffe
             case PIT_DATA_PORT(1):
             case PIT_DATA_PORT(2):
             {
-                PitWriteData(Port - PIT_DATA_PORT(0), *(Address++));
+                PitWriteData(CurrentPort - PIT_DATA_PORT(0), *(Address++));
                 break;
             }
 
             case PIC_MASTER_CMD:
             case PIC_SLAVE_CMD:
             {
-                PicWriteCommand(Port, *(Address++));
+                PicWriteCommand(CurrentPort, *(Address++));
                 break;
             }
 
             case PIC_MASTER_DATA:
             case PIC_SLAVE_DATA:
             {
-                PicWriteData(Port, *(Address++));
+                PicWriteData(CurrentPort, *(Address++));
                 break;
             }
 
@@ -252,13 +256,13 @@ static VOID WINAPI EmulatorWriteIo(PFAST486_STATE State, ULONG Port, PVOID Buffe
             case VGA_STAT_MONO:
             case VGA_STAT_COLOR:
             {
-                VgaWritePort(Port, *(Address++));
+                VgaWritePort(CurrentPort, *(Address++));
                 break;
             }
 
             default:
             {
-                DPRINT1("Write to unknown port: 0x%X\n", Port);
+                DPRINT1("Write to unknown port: 0x%X\n", CurrentPort);
             }
         }
     }