AtTiny13 and AtTiny2313 are considered as avr4 architecture. But they do not support all the instructions of avr4. For example the "mul" instruction does not exist. See bellow a test case for mul.
avr-gcc -mmcu=attiny2313 test_mul.c int main(void) { uint8_t a, b; uint16_t res; res = a * b; } -- Summary: Atmel AVR Tiny13 and Tiny2313 support corrupted Product: gcc Version: 4.0.0 Status: UNCONFIRMED Severity: normal Priority: P1 Component: target AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: frouleau at naotek dot com CC: ericw at evcohs dot com,gcc-bugs at gcc dot gnu dot org GCC build triplet: Any GCC host triplet: Any GCC target triplet: avr http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19059