diff --git a/arch/arm/include/kinetis/chip.h b/arch/arm/include/kinetis/chip.h
index 0e8f216d04..7cbf732620 100644
--- a/arch/arm/include/kinetis/chip.h
+++ b/arch/arm/include/kinetis/chip.h
@@ -48,13 +48,40 @@
 
 /* Get customizations for each supported chip */
 
-#if defined(CONFIG_ARCH_CHIP_MK20DX256VLH7)
+/* MK20DX---VLH7
+ *
+ *  ------------- ------ --- ------- ------ ------- ------ ----- ----
+ *  PART NUMBER   CPU    PIN PACKAGE TOTAL  PROGRAM EEPROM SRAM  GPIO
+ *                FREQ   CNT         FLASH  FLASH
+ *  ------------- ------ --- ------- ------ ------- ------ ----- ----
+ *  MK20DX64VLH7  72 MHz 64  LQFP     96 KB  64 KB  2 KB   16 KB 40
+ *  MK20DX128VLH7 72 MHz 64  LQFP    160 KB 128 KB  2 KB   32 KB 40
+ *  MK20DX256VLH7 72 MHz 64  LQFP    288 KB 256 KB  2 KB   64 KB 40
+ *  ------------- ------ --- ------- ------ ------- ------ ----- ----
+ */
+
+#if defined(CONFIG_ARCH_CHIP_MK20DX64VLH7) || \
+    defined(CONFIG_ARCH_CHIP_MK20DX128VLH7) || \
+    defined(CONFIG_ARCH_CHIP_MK20DX256VLH7)
+
 #  define KINETIS_K20             1          /* Kinetics K20 family */
 #  undef  KINETIS_K40                        /* Not Kinetics K40 family */
 #  undef  KINETIS_K60                        /* Not Kinetis K60 family */
+
+#if defined(CONFIG_ARCH_CHIP_MK20DX64VLH7)
+#  define KINETIS_FLASH_SIZE      (64*1024)  /* 64Kb */
+#  define KINETIS_FLEXMEM_SIZE    (32*1024)  /* 32Kb */
+#  define KINETIS_SRAM_SIZE       (16*1024)  /* 16Kb */
+#elif defined(CONFIG_ARCH_CHIP_MK20DX128VLH7)
+#  define KINETIS_FLASH_SIZE      (128*1024) /* 128Kb */
+#  define KINETIS_FLEXMEM_SIZE    (32*1024)  /* 32Kb */
+#  define KINETIS_SRAM_SIZE       (32*1024)  /* 32Kb */
+#else /* if defined(CONFIG_ARCH_CHIP_MK20DX256VLH7) */
 #  define KINETIS_FLASH_SIZE      (256*1024) /* 256Kb */
 #  define KINETIS_FLEXMEM_SIZE    (32*1024)  /* 32Kb */
 #  define KINETIS_SRAM_SIZE       (64*1024)  /* 64Kb */
+#endif
+
 #  undef  KINETIS_MPU                        /* No memory protection unit */
 #  undef  KINETIS_EXTBUS                     /* No external bus interface */
 #  define KINETIS_NDMACH          16         /* Up to 16 DMA channels */
diff --git a/arch/arm/src/kinetis/Kconfig b/arch/arm/src/kinetis/Kconfig
index ff1fd735c6..88c161de01 100644
--- a/arch/arm/src/kinetis/Kconfig
+++ b/arch/arm/src/kinetis/Kconfig
@@ -10,6 +10,14 @@ choice
 	default ARCH_CHIP_MK60N512VMD100
 	depends on ARCH_CHIP_KINETIS
 
+config ARCH_CHIP_MK20DX64VLH7
+	bool "MK20DX64VLH7"
+	select ARCH_FAMILY_K20
+
+config ARCH_CHIP_MK20DX128VLH7
+	bool "MK20DX128VLH7"
+	select ARCH_FAMILY_K20
+
 config ARCH_CHIP_MK20DX256VLH7
 	bool "MK20DX256VLH7"
 	select ARCH_FAMILY_K20
diff --git a/configs/teensy-3.x/README.txt b/configs/teensy-3.x/README.txt
index 8079ec91e8..94b320b4e8 100644
--- a/configs/teensy-3.x/README.txt
+++ b/configs/teensy-3.x/README.txt
@@ -12,8 +12,22 @@ README
 
   This board configuration can also be used with the older Teensy-3.0.  The
   Teensy-3.0 has the same schematic (although some pins are not used on the
-  Teensy-3.0).  the primary difference is that the Teensy 3.0 has a
-  MK30DX128VLH5 with slightly less capability.
+  Teensy-3.0).  The primary difference is that the Teensy 3.0 has a
+  MK30DX128VLH5 with slightly less capability.  There are many difference
+  between the MK30DX256VLH7 and the MK30DX128VLH5 but the basic differences
+  that effect how you configure NuttX are:
+
+    --------------- -------------- -------------- ---------------------------
+    Feature         Teensy 3.0     Teensy 3.1     CONFIGURATION
+    --------------- -------------- -------------- ---------------------------
+    Processor
+      Core          MK20DX128VLH5  MK20DX256VLH7  CONFIG_ARCH_CHIP_xyz
+      Rated Speed    48 MHz         72 MHz        Settings in include/board.h
+      Overclockable  96 MHz         96 MHz        Settings in include/board.h
+    Flash Memory    128 KB         256 KB         See scripts/flash.ld
+    SRAM             16 KB          64 KB         See scripts/flash.ld and
+                                                  set CONFIG_RAM_SIZE=???
+    --------------- -------------- -------------- ---------------------------
 
 Contents
 ========