diff --git a/common/hw-gfx-gma-pch-sideband.adb b/common/hw-gfx-gma-pch-sideband.adb
new file mode 100644
index 0000000..abbf472
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+++ b/common/hw-gfx-gma-pch-sideband.adb
@@ -0,0 +1,137 @@
+--
+-- Copyright (C) 2015 secunet Security Networks AG
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation; version 2 of the License.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+-- GNU General Public License for more details.
+--
+
+with HW.GFX.GMA.Registers;
+
+package body HW.GFX.GMA.PCH.Sideband is
+
+   SBI_CTL_DEST_ICLK : constant := 0 * 2 ** 16;
+   SBI_CTL_DEST_MPHY : constant := 1 * 2 ** 16;
+   SBI_CTL_OP_IORD   : constant := 2 * 2 **  8;
+   SBI_CTL_OP_IOWR   : constant := 3 * 2 **  8;
+   SBI_CTL_OP_CRRD   : constant := 6 * 2 **  8;
+   SBI_CTL_OP_CRWR   : constant := 7 * 2 **  8;
+
+   SBI_RESPONSE_FAIL : constant := 1 * 2 **  1;
+   SBI_BUSY          : constant := 1 * 2 **  0;
+
+   type Register_Array is array (Register_Type) of Word32;
+   Register_Addr : constant Register_Array := Register_Array'
+     (SBI_SSCDIVINTPHASE6  => 16#0600_0000#,
+      SBI_SSCCTL6          => 16#060c_0000#,
+      SBI_SSCAUXDIV        => 16#0610_0000#);
+
+   ----------------------------------------------------------------------------
+
+   procedure Read
+     (Dest     : in     Destination_Type;
+      Register : in     Register_Type;
+      Value    :    out Word32)
+   is
+   begin
+      Registers.Wait_Unset_Mask
+        (Register => Registers.SBI_CTL_STAT,
+         Mask     => SBI_BUSY);
+
+      Registers.Write
+        (Register => Registers.SBI_ADDR,
+         Value    => Register_Addr (Register));
+
+      if Dest = SBI_ICLK then
+         Registers.Write
+           (Register => Registers.SBI_CTL_STAT,
+            Value    => SBI_CTL_DEST_ICLK or SBI_CTL_OP_CRRD or SBI_BUSY);
+      else
+         Registers.Write
+           (Register => Registers.SBI_CTL_STAT,
+            Value    => SBI_CTL_DEST_MPHY or SBI_CTL_OP_IORD or SBI_BUSY);
+      end if;
+
+      Registers.Wait_Unset_Mask
+        (Register => Registers.SBI_CTL_STAT,
+         Mask     => SBI_BUSY);
+
+      Registers.Read
+        (Register => Registers.SBI_DATA,
+         Value    => Value);
+   end Read;
+
+   procedure Write
+     (Dest     : in     Destination_Type;
+      Register : in     Register_Type;
+      Value    : in     Word32)
+   is
+   begin
+      Registers.Wait_Unset_Mask
+        (Register => Registers.SBI_CTL_STAT,
+         Mask     => SBI_BUSY);
+
+      Registers.Write
+        (Register => Registers.SBI_ADDR,
+         Value    => Register_Addr (Register));
+      Registers.Write
+        (Register => Registers.SBI_DATA,
+         Value    => Value);
+
+      if Dest = SBI_ICLK then
+         Registers.Write
+           (Register => Registers.SBI_CTL_STAT,
+            Value    => SBI_CTL_DEST_ICLK or SBI_CTL_OP_CRWR or SBI_BUSY);
+      else
+         Registers.Write
+           (Register => Registers.SBI_CTL_STAT,
+            Value    => SBI_CTL_DEST_MPHY or SBI_CTL_OP_IOWR or SBI_BUSY);
+      end if;
+
+      Registers.Wait_Unset_Mask
+        (Register => Registers.SBI_CTL_STAT,
+         Mask     => SBI_BUSY);
+   end Write;
+
+   ----------------------------------------------------------------------------
+
+   procedure Unset_Mask
+     (Dest     : in     Destination_Type;
+      Register : in     Register_Type;
+      Mask     : in     Word32)
+   is
+      Value : Word32;
+   begin
+      Read (Dest, Register, Value);
+      Write (Dest, Register, Value and not Mask);
+   end Unset_Mask;
+
+   procedure Set_Mask
+     (Dest     : in     Destination_Type;
+      Register : in     Register_Type;
+      Mask     : in     Word32)
+   is
+      Value : Word32;
+   begin
+      Read (Dest, Register, Value);
+      Write (Dest, Register, Value or Mask);
+   end Set_Mask;
+
+   procedure Unset_And_Set_Mask
+     (Dest        : in     Destination_Type;
+      Register    : in     Register_Type;
+      Mask_Unset  : in     Word32;
+      Mask_Set    : in     Word32)
+   is
+      Value : Word32;
+   begin
+      Read (Dest, Register, Value);
+      Write (Dest, Register, (Value and not Mask_Unset) or Mask_Set);
+   end Unset_And_Set_Mask;
+
+end HW.GFX.GMA.PCH.Sideband;