diff --git a/src/mame/drivers/ampex.cpp b/src/mame/drivers/ampex.cpp
index f168a1a3743..d4d2b27544b 100644
--- a/src/mame/drivers/ampex.cpp
+++ b/src/mame/drivers/ampex.cpp
@@ -26,22 +26,21 @@ private:
 };
 
 static ADDRESS_MAP_START( mem_map, AS_PROGRAM, 8, ampex_state )
-	AM_RANGE(0x0000,0x2fff) AM_ROM AM_REGION("roms", 0)
-	AM_RANGE(0x4000,0x5fff) AM_RAM // devices in this range
-	AM_RANGE(0x8000,0x9fff) AM_RAM
-	AM_RANGE(0xc000,0xcfff) AM_RAM
-ADDRESS_MAP_END
-
-static ADDRESS_MAP_START( io_map, AS_PROGRAM, 8, ampex_state )
+	AM_RANGE(0x0000, 0x2fff) AM_ROM AM_REGION("roms", 0)
+	AM_RANGE(0x4000, 0x43ff) AM_RAM // main RAM
+	AM_RANGE(0x4400, 0x57ff) AM_RAM // expansion RAM
+	AM_RANGE(0x5841, 0x5841) AM_WRITENOP // ???
+	AM_RANGE(0x5842, 0x5842) AM_READNOP // ???
+	AM_RANGE(0x8000, 0x9fff) AM_RAM
+	AM_RANGE(0xc000, 0xcfff) AM_RAM // video RAM
 ADDRESS_MAP_END
 
 static INPUT_PORTS_START( ampex )
 INPUT_PORTS_END
 
 static MACHINE_CONFIG_START( ampex )
-	MCFG_CPU_ADD("maincpu", I8085A, 2'000'000) // no idea of clock. cpu could be 8080.
+	MCFG_CPU_ADD("maincpu", I8080A, 2'000'000) // no idea of clock.
 	MCFG_CPU_PROGRAM_MAP(mem_map)
-	MCFG_CPU_IO_MAP(io_map)
 MACHINE_CONFIG_END
 
 ROM_START( dialog80 )