diff -Naurp gcc/config/avr/avr-devices.c gcc/config/avr/avr-devices.c
--- gcc/config/avr/avr-devices.c	2011-06-24 10:38:47.000000000 +0530
+++ gcc/config/avr/avr-devices.c	2011-06-24 10:38:36.000000000 +0530
@@ -262,6 +262,7 @@ const struct mcu_type_s avr_mcu_types[] 
     /* Xmega, > 64K, <= 128K FLASH, <= 64K RAM.  */
   { "avrxmega4",    ARCH_AVRXMEGA4, NULL,                           0, 0x2000, "x64d3" },
   { "atxmega64a3",  ARCH_AVRXMEGA4, "__AVR_ATxmega64A3__",          0, 0x2000, "x64a3" },
+  { "atxmega64a3u", ARCH_AVRXMEGA4, "__AVR_ATxmega64A3U__",         0, 0x2000, "x64a3u"},
   { "atxmega64d3",  ARCH_AVRXMEGA4, "__AVR_ATxmega64D3__",          0, 0x2000, "x64d3" },
     /* Xmega, > 64K, <= 128K FLASH, > 64K RAM.  */
   { "avrxmega5",    ARCH_AVRXMEGA5, NULL,                           0, 0x2000, "x64a1" },
@@ -270,11 +271,14 @@ const struct mcu_type_s avr_mcu_types[] 
     /* Xmega, > 128K, <= 256K FLASH, <= 64K RAM.  */
   { "avrxmega6",    ARCH_AVRXMEGA6, NULL,                           0, 0x2000, "x128a3" },
   { "atxmega128a3", ARCH_AVRXMEGA6, "__AVR_ATxmega128A3__",         0, 0x2000, "x128a3" },
+  { "atxmega128a3u",ARCH_AVRXMEGA6, "__AVR_ATxmega128A3U__",        0, 0x2000, "x128a3u"},
   { "atxmega128b1", ARCH_AVRXMEGA6, "__AVR_ATxmega128B1__",         0, 0x2000, "x128b1" },
   { "atxmega128d3", ARCH_AVRXMEGA6, "__AVR_ATxmega128D3__",         0, 0x2000, "x128d3" },
   { "atxmega192a3", ARCH_AVRXMEGA6, "__AVR_ATxmega192A3__",         0, 0x2000, "x192a3" },
+  { "atxmega192a3u",ARCH_AVRXMEGA6, "__AVR_ATxmega192A3U__",        0, 0x2000, "x192a3u"},
   { "atxmega192d3", ARCH_AVRXMEGA6, "__AVR_ATxmega192D3__",         0, 0x2000, "x192d3" },
   { "atxmega256a3", ARCH_AVRXMEGA6, "__AVR_ATxmega256A3__",         0, 0x2000, "x256a3" },
+  { "atxmega256a3u",ARCH_AVRXMEGA6, "__AVR_ATxmega256A3U__",        0, 0x2000, "x256a3u"},
   { "atxmega256a3b",ARCH_AVRXMEGA6, "__AVR_ATxmega256A3B__",        0, 0x2000, "x256a3b" },
   { "atxmega256a3bu", ARCH_AVRXMEGA6, "__AVR_ATxmega256A3BU__",     0, 0x2000, "x256a3bu" },
   { "atxmega256d3", ARCH_AVRXMEGA6, "__AVR_ATxmega256D3__",         0, 0x2000, "x256d3" },
diff -Naurp gcc/config/avr/t-avr gcc/config/avr/t-avr
--- gcc/config/avr/t-avr	2011-06-24 10:38:47.000000000 +0530
+++ gcc/config/avr/t-avr	2011-06-24 10:38:36.000000000 +0530
@@ -272,15 +272,19 @@ MULTILIB_MATCHES = \
 	mmcu?avrxmega2=mmcu?atxmega32a4u \
 	mmcu?avrxmega2=mmcu?atxmega32x1 \
 	mmcu?avrxmega4=mmcu?atxmega64a3 \
+	mmcu?avrxmega4=mmcu?atxmega64a3u \
 	mmcu?avrxmega4=mmcu?atxmega64d3 \
 	mmcu?avrxmega5=mmcu?atxmega64a1 \
 	mmcu?avrxmega5=mmcu?atxmega64a1u \
 	mmcu?avrxmega6=mmcu?atxmega128a3 \
+	mmcu?avrxmega6=mmcu?atxmega128a3u \
 	mmcu?avrxmega6=mmcu?atxmega128b1 \
 	mmcu?avrxmega6=mmcu?atxmega128d3 \
 	mmcu?avrxmega6=mmcu?atxmega192a3 \
+	mmcu?avrxmega6=mmcu?atxmega192a3u \
 	mmcu?avrxmega6=mmcu?atxmega192d3 \
 	mmcu?avrxmega6=mmcu?atxmega256a3 \
+	mmcu?avrxmega6=mmcu?atxmega256a3u \
 	mmcu?avrxmega6=mmcu?atxmega256a3b \
 	mmcu?avrxmega6=mmcu?atxmega256a3bu \
 	mmcu?avrxmega6=mmcu?atxmega256d3 \