diff --git a/sparkfun/samd/boards.txt b/sparkfun/samd/boards.txt
index bdac485f..5d766b21 100644
--- a/sparkfun/samd/boards.txt
+++ b/sparkfun/samd/boards.txt
@@ -155,6 +155,62 @@ samd21_proRF.build.pid=0x214F
 samd21_proRF.bootloader.tool=openocd
 samd21_proRF.bootloader.file=zero/Sparkfun_SAMD21_ProRF.bin
 
+samd21_proRF_no_bl.name=SparkFun SAMD21 Pro RF (no bootloader, 8 MHz)
+samd21_proRF_no_bl.vid.0=0x1B4F
+samd21_proRF_no_bl.pid.0=0x214F
+samd21_proRF_no_bl.vid.1=0x1B4F
+samd21_proRF_no_bl.pid.1=0x215F
+samd21_proRF_no_bl.upload.tool=bossac
+samd21_proRF_no_bl.upload.protocol=sam-ba
+samd21_proRF_no_bl.upload.maximum_size=262144
+samd21_proRF_no_bl.upload.use_1200bps_touch=true
+samd21_proRF_no_bl.upload.wait_for_upload_port=true
+samd21_proRF_no_bl.upload.native_usb=true
+samd21_proRF_no_bl.build.mcu=cortex-m0plus
+samd21_proRF_no_bl.build.f_cpu=8000000L
+samd21_proRF_no_bl.build.usb_product="SFE SAMD21 Pro RF"
+samd21_proRF_no_bl.build.usb_manufacturer="SparkFun"
+samd21_proRF_no_bl.build.board=SAMD_ZERO
+samd21_proRF_no_bl.build.core=arduino
+samd21_proRF_no_bl.build.extra_flags=-D__SAMD21G18A__ {build.usb_flags}
+samd21_proRF_no_bl.build.ldscript=linker_scripts/gcc/flash_without_bootloader.ld
+samd21_proRF_no_bl.build.openocdscript=openocd_scripts/arduino_zero.cfg
+samd21_proRF_no_bl.build.variant=SparkFun_ProRF
+samd21_proRF_no_bl.build.variant_system_lib=
+samd21_proRF_no_bl.build.extra_combine_flags=
+samd21_proRF_no_bl.build.vid=0x1B4F
+samd21_proRF_no_bl.build.pid=0x214F
+samd21_proRF_no_bl.bootloader.tool=openocd
+samd21_proRF_no_bl.bootloader.file=zero/Sparkfun_SAMD21_ProRF.bin
+
+samd21_proRF_no_bl_24.name=SparkFun SAMD21 Pro RF (no bootloader, 24 MHz)
+samd21_proRF_no_bl_24.vid.0=0x1B4F
+samd21_proRF_no_bl_24.pid.0=0x214F
+samd21_proRF_no_bl_24.vid.1=0x1B4F
+samd21_proRF_no_bl_24.pid.1=0x215F
+samd21_proRF_no_bl_24.upload.tool=bossac
+samd21_proRF_no_bl_24.upload.protocol=sam-ba
+samd21_proRF_no_bl_24.upload.maximum_size=262144
+samd21_proRF_no_bl_24.upload.use_1200bps_touch=true
+samd21_proRF_no_bl_24.upload.wait_for_upload_port=true
+samd21_proRF_no_bl_24.upload.native_usb=true
+samd21_proRF_no_bl_24.build.mcu=cortex-m0plus
+samd21_proRF_no_bl_24.build.f_cpu=24000000L
+samd21_proRF_no_bl_24.build.usb_product="SFE SAMD21 Pro RF"
+samd21_proRF_no_bl_24.build.usb_manufacturer="SparkFun"
+samd21_proRF_no_bl_24.build.board=SAMD_ZERO
+samd21_proRF_no_bl_24.build.core=arduino
+samd21_proRF_no_bl_24.build.extra_flags=-D__SAMD21G18A__ {build.usb_flags}
+samd21_proRF_no_bl_24.build.ldscript=linker_scripts/gcc/flash_without_bootloader.ld
+samd21_proRF_no_bl_24.build.openocdscript=openocd_scripts/arduino_zero.cfg
+samd21_proRF_no_bl_24.build.variant=SparkFun_ProRF
+samd21_proRF_no_bl_24.build.variant_system_lib=
+samd21_proRF_no_bl_24.build.extra_combine_flags=
+samd21_proRF_no_bl_24.build.vid=0x1B4F
+samd21_proRF_no_bl_24.build.pid=0x214F
+samd21_proRF_no_bl_24.bootloader.tool=openocd
+samd21_proRF_no_bl_24.bootloader.file=zero/Sparkfun_SAMD21_ProRF.bin
+
 samd21_proRF_1w.name=SparkFun SAMD21 Pro RF 1W
 samd21_proRF_1w.vid.0=0x1B4F
 samd21_proRF_1w.pid.0=0x8D21
diff --git a/sparkfun/samd/cores/arduino/startup.c b/sparkfun/samd/cores/arduino/startup.c
index d66bfa8e..27e9cd07 100644
--- a/sparkfun/samd/cores/arduino/startup.c
+++ b/sparkfun/samd/cores/arduino/startup.c
@@ -227,7 +227,13 @@ void SystemInit( void )
   /* ----------------------------------------------------------------------------------------------
    * 5) Switch Generic Clock Generator 0 to DFLL48M. CPU will run at 48MHz.
    */
+#if F_CPU != 8000000L
+
+#if F_CPU == 24000000L
+  GCLK->GENDIV.reg = GCLK_GENDIV_DIV(2) | GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_MAIN ) ; // Generic Clock Generator 0
+#else
   GCLK->GENDIV.reg = GCLK_GENDIV_ID( GENERIC_CLOCK_GENERATOR_MAIN ) ; // Generic Clock Generator 0
+#endif
 
   while ( GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY )
   {
@@ -245,6 +251,7 @@ void SystemInit( void )
   {
     /* Wait for synchronization */
   }
+#endif
 
   /* ----------------------------------------------------------------------------------------------
    * 6) Modify PRESCaler value of OSC8M to have 8MHz
@@ -277,7 +284,8 @@ void SystemInit( void )
   PM->APBBSEL.reg = PM_APBBSEL_APBBDIV_DIV1_Val ;
   PM->APBCSEL.reg = PM_APBCSEL_APBCDIV_DIV1_Val ;
 
-  SystemCoreClock=VARIANT_MCK ;
+  //SystemCoreClock=VARIANT_MCK ;
+  SystemCoreClock = F_CPU;
 
   /* ----------------------------------------------------------------------------------------------
    * 8) Load ADC factory calibration values
diff --git a/sparkfun/samd/platform.txt b/sparkfun/samd/platform.txt
index c145b308..e4cc19fc 100644
--- a/sparkfun/samd/platform.txt
+++ b/sparkfun/samd/platform.txt
@@ -183,7 +183,7 @@ tools.openocd.erase.pattern=
 
 tools.openocd.bootloader.params.verbose=-d2
 tools.openocd.bootloader.params.quiet=-d0
-tools.openocd.bootloader.pattern="{path}/{cmd}" {bootloader.verbose} -s "{path}/share/openocd/scripts/" -f "{runtime.platform.path}/variants/{build.variant}/{build.openocdscript}" -c "telnet_port disabled; init; halt; at91samd bootloader 0; program {{{runtime.platform.path}/bootloaders/{bootloader.file}}} verify reset; shutdown"
+tools.openocd.bootloader.pattern="{path}/{cmd}" {bootloader.verbose} -s "{path}/share/openocd/scripts/" -f "{runtime.platform.path}/variants/{build.variant}/{build.openocdscript}" -c "telnet_port disabled; init; halt; at91samd bootloader 0; program {{runtime.platform.path}/bootloaders/{bootloader.file}} verify reset; shutdown"
 
 #
 # OpenOCD sketch upload - version with configurable bootloader size
@@ -210,4 +210,4 @@ tools.openocd-withbootsize.erase.pattern=
 
 tools.openocd-withbootsize.bootloader.params.verbose=-d2
 tools.openocd-withbootsize.bootloader.params.quiet=-d0
-tools.openocd-withbootsize.bootloader.pattern="{path}/{cmd}" {bootloader.verbose} -s "{path}/share/openocd/scripts/" -f "{runtime.platform.path}/variants/{build.variant}/{build.openocdscript}" -c "telnet_port disabled; init; halt; at91samd bootloader 0; program {{{runtime.platform.path}/bootloaders/{bootloader.file}}} verify reset; shutdown"
+tools.openocd-withbootsize.bootloader.pattern="{path}/{cmd}" {bootloader.verbose} -s "{path}/share/openocd/scripts/" -f "{runtime.platform.path}/variants/{build.variant}/{build.openocdscript}" -c "telnet_port disabled; init; halt; at91samd bootloader 0; program {{runtime.platform.path}/bootloaders/{bootloader.file}} verify reset; shutdown"