diff --git a/src/mame/drivers/cps1.c b/src/mame/drivers/cps1.c
index 464d9cc7bfb..8a0502ce36c 100644
--- a/src/mame/drivers/cps1.c
+++ b/src/mame/drivers/cps1.c
@@ -3072,6 +3072,10 @@ ROM_START( forgott1 )
 	ROM_LOAD( "prg1",         0x0000, 0x0117, CRC(f1129744) SHA1(a5300f301c1a08a7da768f0773fa0fe3f683b237) )
 	ROM_LOAD( "rom1",         0x0000, 0x0117, CRC(41dc73b9) SHA1(7d4c9f1693c821fbf84e32dd6ef62ddf14967845) )
 	ROM_LOAD( "sou1",         0x0000, 0x0117, CRC(84f4b2fe) SHA1(dcc9e86cc36316fe42eace02d6df75d08bc8bb6d) )
+
+	ROM_REGION( 0x0200, "bboardplds", ROMREGION_DISPOSE )
+	ROM_LOAD( "lw621.1a",     0x0000, 0x0117, CRC(5eec6ce9) SHA1(5ec8b60f1f1bdba865b1fa2387987ce99ff4093a) )
+	ROM_LOAD( "lwio.12b",     0x0000, 0x0117, CRC(ad52b90c) SHA1(f0fd6aeea515ee449320fe15684e6b3ab7f97bf4) )
 ROM_END
 
 /* B-Board 88618B */
diff --git a/src/mame/video/cps1.c b/src/mame/video/cps1.c
index 003bfb2271b..626c812da52 100644
--- a/src/mame/video/cps1.c
+++ b/src/mame/video/cps1.c
@@ -433,6 +433,9 @@ CPS_B_21_QSx are various battery configurations in Q-Sound games
 */
 
 
+// LWCHR and LW621 are equivalent as far as the game is concerned, though the
+// equations are different
+
 #define mapper_LWCHR	{ 0x8000, 0x8000, 0, 0 }, mapper_LWCHR_table
 static const struct gfx_range mapper_LWCHR_table[] =
 {
@@ -452,6 +455,38 @@ static const struct gfx_range mapper_LWCHR_table[] =
 	{ 0 }
 };
 
+#define mapper_LW621	{ 0x8000, 0x8000, 0, 0 }, mapper_LW621_table
+static const struct gfx_range mapper_LW621_table[] =
+{
+	// verified from PAL dump (PAL @ 1A):
+	// bank 0 = pin 18
+	// bank 1 = pin 14
+	// pins 19, 16, 17, and 12 give an alternate half-size mapping which would
+	// allow to use smaller ROMs:
+	// pin 19
+	// 0 00000-03fff
+	// pin 16
+	// 0 04000-07fff
+	// 1 00000-1ffff
+	// pin 17
+	// 2 00000-1ffff
+	// 3 00000-1ffff
+	// 4 00000-1ffff
+	// pin 12
+	// 3 00000-1ffff
+	//
+	// note that allowed codes go up to 0x1ffff but physical ROM is half that size
+
+	/* type            start    end      bank */
+	{ GFXTYPE_SPRITES, 0x00000, 0x07fff, 0 },
+	{ GFXTYPE_SCROLL1, 0x00000, 0x1ffff, 0 },
+
+	{ GFXTYPE_STARS,   0x00000, 0x1ffff, 1 },
+	{ GFXTYPE_SCROLL2, 0x00000, 0x1ffff, 1 },
+	{ GFXTYPE_SCROLL3, 0x00000, 0x1ffff, 1 },
+	{ 0 }
+};
+
 
 // DM620, DM22A and DAM63B are equivalent as far as the game is concerned, though
 // the equations are quite different
@@ -1199,7 +1234,7 @@ static const struct CPS1config cps1_config_table[]=
 {
 	/* name       CPSB         gfx mapper   in2  in3  out2   kludge */
 	{"forgottn", CPS_B_01,     mapper_LWCHR },
-	{"forgott1", CPS_B_01,     mapper_LWCHR },
+	{"forgott1", CPS_B_01,     mapper_LW621 },
 	{"lostwrld", CPS_B_01,     mapper_LWCHR },
 	{"ghouls",   CPS_B_01,     mapper_DM620 },
 	{"ghoulsu",  CPS_B_01,     mapper_DM620 },