#### 9.5.1 Options

`-mmcu=mcu`

  Specify ATMEL AVR instruction set or MCU type.

  Instruction set avr1 is for the minimal AVR core, not supported by the C compiler, only for assembler programs (MCU types: at90s1200, attiny11, attiny12, attiny15, attiny28).

  Instruction set avr2 (default) is for the classic AVR core with up to 8K program memory space (MCU types: at90s2313, at90s2323, at90s2333, at90s2343, attiny22, attiny26, at90s4414, at90s4433, at90s4434, at90s8515, at90c8534, at90s8535).

  Instruction set avr25 is for the classic AVR core with up to 8K program memory space plus the MOVW instruction (MCU types: attiny13, attiny13a, attiny2313, attiny2313a, attiny24, attiny24a, attiny4313, attiny44, attiny44a, attiny84, attiny84a, attiny25, attiny45, attiny85, attiny261, attiny261a, attiny461, attiny461a, attiny861, attiny861a, attiny87, attiny43u, attiny48, attiny88, attiny828, at86rf401, ata6289, ata5272).

  Instruction set avr3 is for the classic AVR core with up to 128K program memory space (MCU types: at43usb355, at76c711).

  Instruction set avr31 is for the classic AVR core with exactly 128K program memory space (MCU types: atmega103, at43usb320).

  Instruction set avr35 is for classic AVR core plus MOVW, CALL, and JMP instructions (MCU types: attiny167, attiny1634, at90usb82, at90usb162, atmega8u2, atmega16u2, atmega32u2, ata5505).

  Instruction set avr4 is for the enhanced AVR core with up to 8K program memory space (MCU types: atmega48, atmega48a, atmega48pa, atmega48p, atmega8, atmega8a, atmega88, atmega88a, atmega88p, atmega88pa, atmega8515, atmega8535, atmega8hva, at90pwm1, at90pwm2, at90pwm2b, at90pwm3, at90pwm3b, at90pwm81, ata6285, ata6286).

  Instruction set avr5 is for the enhanced AVR core with up to 128K program memory space (MCU types: at90pwm161, atmega16, atmega16a, atmega161, atmega162, atmega163, atmega164a, atmega164p, atmega164pa, atmega165, atmega165a, atmega165p, atmega165pa, atmega168, atmega168a, atmega168p, atmega168pa, atmega169, atmega169a, atmega169p, atmega169pa, atmega32, atmega323, atmega324a, atmega324p, atmega324pa, atmega325, atmega325a, atmega32, atmega32a, atmega323, atmega324a, atmega324p, atmega324pa, atmega325, atmega325a, atmega325p, atmega325p, atmega325pa, atmega3250, atmega3250a, atmega3250p, atmega3250pa, atmega328, atmega328p, atmega329, atmega329a, atmega329p, atmega329pa, atmega3290a, atmega3290p, atmega3290pa, atmega406, atmega64, atmega64a, atmega64rfr2, atmega644rfr2, atmega640, atmega644, atmega644a, atmega644p, atmega644pa, atmega645, atmega645a, atmega645p, atmega6450, atmega6450a, atmega6450p, atmega649, atmega649a, atmega649p, atmega6490, atmega6490a, atmega6490p, atmega16hva, atmega16hva2, atmega16hvb, atmega16hvbrevb, atmega32hvb, atmega32hvbrevb, atmega64hve, at90can32, at90can64, at90pwm161, at90pwm216, at90pwm316, atmega32c1, atmega64c1, atmega16m1, atmega32m1, atmega64m1, atmega16u4, atmega32u4, atmega32u6, at90usb646, at90usb647, at94k, at90scr100, ata5790, ata5795).

  Instruction set avr51 is for the enhanced AVR core with exactly 128K program memory space (MCU types: atmega128, atmega128a, atmega1280, atmega1281, atmega1284, atmega1284p, atmega128rfa1, atmega128rfr2, atmega1284rfr2, at90can128, at90usb1286, at90usb1287, m3000).

  Instruction set avr6 is for the enhanced AVR core with a 3-byte PC (MCU types: atmega2560, atmega2561, atmega256rfr2, atmega2564rfr2).

  Instruction set avrxmega2 is for the XMEGA AVR core with 8K to 64K program memory space and less than 64K data space (MCU types: atxmega16a4, atxmega16a4u, atxmega16c4, atxmega16d4, atxmega16x1, atxmega32a4, atxmega32a4u, atxmega32c4, atxmega32d4, atxmega16e5, atxmega8e5, atxmega32e5, atxmega32x1).

  Instruction set avrxmega3 is for the XMEGA AVR core with up to 64K of combined program memory and RAM, and with program memory visible in the RAM address space (MCU types: attiny212, attiny214, attiny412, attiny414, attiny416, attiny417, attiny814, attiny816, attiny817, attiny1614, attiny1616, attiny1617, attiny3214, attiny3216, attiny3217).

  Instruction set avrxmega4 is for the XMEGA AVR core with up to 64K program memory space and less than 64K data space (MCU types: atxmega64a3, atxmega64a3u, atxmega64a4u, atxmega64b1, atxmega64b3, atxmega64c3, atxmega64d3, atxmega64d4).

  Instruction set avrxmega5 is for the XMEGA AVR core with up to 64K program memory space and greater than 64K data space (MCU types: atxmega64a1, atxmega64a1u).

  Instruction set avrxmega6 is for the XMEGA AVR core with larger than 64K program memory space and less than 64K data space (MCU types: atxmega128a3, atxmega128a3u, atxmega128c3, atxmega128d3, atxmega128d4, atxmega192a3, atxmega192a3u, atxmega128b1, atxmega128b3, atxmega192c3, atxmega192d3, atxmega256a3, atxmega256a3u, atxmega256a3b, atxmega256a3bu, atxmega256c3, atxmega256d3, atxmega384c3, atxmega256d3).

  Instruction set avrxmega7 is for the XMEGA AVR core with larger than 64K program memory space and greater than 64K data space (MCU types: atxmega128a1, atxmega128a1u, atxmega128a4u).

  Instruction set avrtiny is for the ATtiny4/5/9/10/20/40 microcontrollers.

`-mall-opcodes`

  Accept all AVR opcodes, even if not supported by `-mmcu`.

`-mno-skip-bug`

  This option disable warnings for skipping two-word instructions.

`-mno-wrap`

  This option reject `rjmp/rcall` instructions with 8K wrap-around.

`-mrmw`

  Accept Read-Modify-Write (`XCH,LAC,LAS,LAT`) instructions.

`-mlink-relax`

  Enable support for link-time relaxation. This is now on by default and this flag no longer has any effect.

`-mno-link-relax`

  Disable support for link-time relaxation. The assembler will resolve relocations when it can, and may be able to better compress some debug information.

`-mgcc-isr`

  Enable the `__gcc_isr` pseudo instruction.