diff --git a/src/mame/machine/saturn_cdb.cpp b/src/mame/machine/saturn_cdb.cpp
index 216a29cfa75..fe0a8455831 100644
--- a/src/mame/machine/saturn_cdb.cpp
+++ b/src/mame/machine/saturn_cdb.cpp
@@ -7,6 +7,8 @@ YGR019B - Hitachi YGR019B CD-Subsystem LSI. Earlier revision is YGR019A. Later r
         into one IC (YGR022 315-5962). The SH1 and the YGR019B make up the 'CD Block' CD Authentication and CD I/O data controller.
         Another of it's functions is to prevent copied CDs from being played
 
+Attempts to use SCI, tight loops checking bit 2 of 0x5ffffc2 (TEIE)
+		
 */
 
 #include "emu.h"
@@ -25,6 +27,11 @@ void saturn_cdb_device::device_start()
 
 static ADDRESS_MAP_START( saturn_cdb_map, AS_PROGRAM, 32, saturn_cdb_device )
 	AM_RANGE(0x00000000, 0x0000ffff) AM_ROM
+	AM_RANGE(0x01000000, 0x010fffff) AM_RAM // RAM buffer area?
+	AM_RANGE(0x02000000, 0x0200003f) AM_RAM // i/f with SH-2s
+	AM_RANGE(0x02100000, 0x0210003f) AM_RAM // i/f with SH-2s
+	AM_RANGE(0x02180000, 0x0218003f) AM_RAM // i/f with SH-2s
+	AM_RANGE(0x07000000, 0x07000fff) AM_RAM // unknown, internal RAM?
 ADDRESS_MAP_END
 
 MACHINE_CONFIG_MEMBER( saturn_cdb_device::device_add_mconfig )