diff --git a/avr/boards.txt b/avr/boards.txt
index e9741f0f..1e4e0626 100644
--- a/avr/boards.txt
+++ b/avr/boards.txt
@@ -243,6 +243,18 @@ menu.baudrate=Baud rate
 328.menu.clock.1MHz_internal.build.clkpr=
 328.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
+328.menu.clock.500k_internal=Internal 500 kHz
+328.menu.clock.500k_internal.upload.default_speed=9600
+328.menu.clock.500k_internal.bootloader.low_fuses=0xc2
+328.menu.clock.500k_internal.build.clkpr=-DOSC_PRESCALER=0x04
+328.menu.clock.500k_internal.build.f_cpu=500000L
+
+328.menu.clock.250k_internal=Internal 250 kHz
+328.menu.clock.250k_internal.upload.default_speed=9600
+328.menu.clock.250k_internal.bootloader.low_fuses=0xc2
+328.menu.clock.250k_internal.build.clkpr=-DOSC_PRESCALER=0x05
+328.menu.clock.250k_internal.build.f_cpu=250000L
+
 
 #############################
 #### ATmega168/A/P/PA/PB ####
@@ -463,6 +475,18 @@ menu.baudrate=Baud rate
 168.menu.clock.1MHz_internal.build.clkpr=
 168.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
+168.menu.clock.500k_internal=Internal 500 kHz
+168.menu.clock.500k_internal.upload.default_speed=9600
+168.menu.clock.500k_internal.bootloader.low_fuses=0xc2
+168.menu.clock.500k_internal.build.clkpr=-DOSC_PRESCALER=0x04
+168.menu.clock.500k_internal.build.f_cpu=500000L
+
+168.menu.clock.250k_internal=Internal 250 kHz
+168.menu.clock.250k_internal.upload.default_speed=9600
+168.menu.clock.250k_internal.bootloader.low_fuses=0xc2
+168.menu.clock.250k_internal.build.clkpr=-DOSC_PRESCALER=0x05
+168.menu.clock.250k_internal.build.f_cpu=250000L
+
 
 ############################
 #### ATmega88/A/P/PA/PB ####
@@ -682,6 +706,18 @@ menu.baudrate=Baud rate
 88.menu.clock.1MHz_internal.build.clkpr=
 88.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
+88.menu.clock.500k_internal=Internal 500 kHz
+88.menu.clock.500k_internal.upload.default_speed=9600
+88.menu.clock.500k_internal.bootloader.low_fuses=0xc2
+88.menu.clock.500k_internal.build.clkpr=-DOSC_PRESCALER=0x04
+88.menu.clock.500k_internal.build.f_cpu=500000L
+
+88.menu.clock.250k_internal=Internal 250 kHz
+88.menu.clock.250k_internal.upload.default_speed=9600
+88.menu.clock.250k_internal.bootloader.low_fuses=0xc2
+88.menu.clock.250k_internal.build.clkpr=-DOSC_PRESCALER=0x05
+88.menu.clock.250k_internal.build.f_cpu=250000L
+
 
 ############################
 #### ATmega48/A/P/PA/PB ####
@@ -904,6 +940,19 @@ menu.baudrate=Baud rate
 48.menu.clock.1MHz_internal.build.clkpr=
 48.menu.clock.1MHz_internal.build.f_cpu=1000000L
 
+48.menu.clock.500k_internal=Internal 500 kHz
+48.menu.clock.500k_internal.upload.default_speed=9600
+48.menu.clock.500k_internal.bootloader.low_fuses=0xc2
+48.menu.clock.500k_internal.build.clkpr=-DOSC_PRESCALER=0x04
+48.menu.clock.500k_internal.build.f_cpu=500000L
+
+48.menu.clock.250k_internal=Internal 250 kHz
+48.menu.clock.250k_internal.upload.default_speed=9600
+48.menu.clock.250k_internal.bootloader.low_fuses=0xc2
+48.menu.clock.250k_internal.build.clkpr=-DOSC_PRESCALER=0x05
+48.menu.clock.250k_internal.build.f_cpu=250000L
+
+
 
 ###################
 #### ATmega8/A ####