Originally Posted by Justin
the PORT_CODE changes should be enough.
Done. SVN diff:
Code

Index: src/mess/drivers/mc1000.c
===================================================================
--- src/mess/drivers/mc1000.c	(revision 9454)
+++ src/mess/drivers/mc1000.c	(working copy)
@@ -237,8 +237,8 @@
 	PORT_BIT( 0xc0, IP_ACTIVE_LOW, IPT_UNUSED )
 
 	PORT_START("MODIFIERS")
-	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_KEYBOARD ) PORT_NAME("SHIFT") PORT_CODE(KEYCODE_LSHIFT) PORT_CHAR(UCHAR_SHIFT_1)
-	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_KEYBOARD ) PORT_NAME("CTRL") PORT_CODE(KEYCODE_RCONTROL) PORT_CHAR(UCHAR_MAMEKEY(RCONTROL))
+	PORT_BIT( 0x40, IP_ACTIVE_LOW, IPT_KEYBOARD ) PORT_NAME("SHIFT") PORT_CODE(KEYCODE_LSHIFT) PORT_CODE(KEYCODE_RSHIFT) PORT_CHAR(UCHAR_SHIFT_1)
+	PORT_BIT( 0x80, IP_ACTIVE_LOW, IPT_KEYBOARD ) PORT_NAME("CTRL") PORT_CODE(KEYCODE_LCONTROL) PORT_CODE(KEYCODE_RCONTROL) PORT_CHAR(UCHAR_MAMEKEY(LCONTROL)) PORT_CHAR(UCHAR_MAMEKEY(RCONTROL))
 
 	PORT_INCLUDE( m6847_artifacting )
 INPUT_PORTS_END