Fork from http://sourceforge.net/projects/ard-core13/ (http://forum.arduino.cc/index.php/topic,89781.0.html)

Includes some compilation errors fixes.

Includes changes made by aleksey_ua from Arduino Forum. (http://forum.arduino.cc/index.php?topic=89781.msg2363643#msg2363643)

Copy attiny13 directory to /opt/arduino-<version>/hardware/.

Copy attiny13 directory into /Applications/Arduino.app/Contents/Java/hardware/.

Copy attiny13 directory into C:\arduino\arduino-<version>\hardware.

Default ArduinoISP sketch too fast for attiny13 @ 128 or 600 KHz ("Invalid device signature" error). To fix that, in ArduinoISP sketch change string:

#define SPI_CLOCK (1000000/6)

with:

#define SPI_CLOCK (128000/6)

If you've got a brand new attiny13a you probably have to set proper fuse bits before you start programming your chip. It's just simple one line command - see details in fusebits-set-attiny13a.txt. I couldn't even burn the bootloader before I set proper fuse bits for my MCU.