user2902: I'm trying to program my ATtiny 13 - 20PU. An it seems to work, but there is no action upon the "delay" command. If on the sketch below I comment out the "High" line, my led is off all the time and whenever I have a Pin 4 High, it's on all the time! Basically this seems to be a frequency/fuse/bootloader problem and made me think the upload was broken.
I added a led between the tiny's pin 3 (digital pin 4) and ground with a 1k current limiting resistor. This one is for testing with the attached sketch.
I also tried this breadboard circuit, which gives exactly the same results.
Upon upload to the tiny I get this:
Sketch uses 380 bytes (37%) of program storage space. Maximum is 1,024 bytes.
Global variables use 8 bytes of dynamic memory.

(Everybody warns about 2 errors occuring upon a proper upload - I don't get those).
My boards.txt look like this:
menu.cpu=Processor
menu.clock=Clock

attiny.name=ATtiny
attiny.bootloader.tool=arduino:avrdude
attiny.bootloader.unlock_bits=0xff
attiny.bootloader.lock_bits=0xff
attiny.build.core=arduino:arduino
attiny.build.board=attiny
attiny.upload.tool=arduino:avrdude

attiny.menu.cpu.attiny45=ATtiny45
attiny.menu.cpu.attiny45.upload.maximum_size=4096
attiny.menu.cpu.attiny45.build.mcu=attiny45
attiny.menu.cpu.attiny45.build.variant=tiny8

attiny.menu.cpu.attiny85=ATtiny85
attiny.menu.cpu.attiny85.upload.maximum_size=8192
attiny.menu.cpu.attiny85.build.mcu=attiny85
attiny.menu.cpu.attiny85.build.variant=tiny8

attiny.menu.cpu.attiny44=ATtiny44
attiny.menu.cpu.attiny44.upload.maximum_size=4096
attiny.menu.cpu.attiny44.build.mcu=attiny44
attiny.menu.cpu.attiny44.build.variant=tiny14

attiny.menu.cpu.attiny84=ATtiny84
attiny.menu.cpu.attiny84.upload.maximum_size=8192
attiny.menu.cpu.attiny84.build.mcu=attiny84
attiny.menu.cpu.attiny84.build.variant=tiny14

attiny.menu.clock.internal1=1 MHz (internal)
attiny.menu.clock.internal1.bootloader.low_fuses=0x62
attiny.menu.clock.internal1.bootloader.high_fuses=0xdf
attiny.menu.clock.internal1.bootloader.extended_fuses=0xff
attiny.menu.clock.internal1.build.f_cpu=1000000L

attiny.menu.clock.internal8=8 MHz (internal)
attiny.menu.clock.internal8.bootloader.low_fuses=0xe2
attiny.menu.clock.internal8.bootloader.high_fuses=0xdf
attiny.menu.clock.internal8.bootloader.extended_fuses=0xff
attiny.menu.clock.internal8.build.f_cpu=8000000L

attiny.menu.clock.external8=8 MHz (external)
attiny.menu.clock.external8.bootloader.low_fuses=0xfe
attiny.menu.clock.external8.bootloader.high_fuses=0xdf
attiny.menu.clock.external8.bootloader.extended_fuses=0xff
attiny.menu.clock.external8.build.f_cpu=8000000L

attiny.menu.clock.external16=16 MHz (external)
attiny.menu.clock.external16.bootloader.low_fuses=0xfe
attiny.menu.clock.external16.bootloader.high_fuses=0xdf
attiny.menu.clock.external16.bootloader.extended_fuses=0xff
attiny.menu.clock.external16.build.f_cpu=16000000L

attiny.menu.clock.external20=20 MHz (external)
attiny.menu.clock.external20.bootloader.low_fuses=0xfe
attiny.menu.clock.external20.bootloader.high_fuses=0xdf
attiny.menu.clock.external20.bootloader.extended_fuses=0xff
attiny.menu.clock.external20.build.f_cpu=20000000L


#################################################
attiny.menu.cpu.attiny13=ATtiny13
attiny.menu.cpu.attiny13.upload.maximum_size=1024
attiny.menu.cpu.attiny13.build.mcu=attiny13
attiny.menu.cpu.attiny13.build.variant=core13

attiny.menu.clock.internal96=9.6MHz (internal)
attiny.menu.clock.internal96.bootloader.low_fuses=0x7A
attiny.menu.clock.internal96.bootloader.high_fuses=0xff
attiny.menu.clock.internal96.build.f_cpu=9600000L
################################################

attiny.menu.clock.internal48=4.8MHz (internal)
attiny.menu.clock.internal48.bootloader.low_fuses=0x79
attiny.menu.clock.internal48.bootloader.high_fuses=0xff
attiny.menu.clock.internal48.build.f_cpu=4800000L
################################################

And I choose the settings: Board ATtiny, Processor ATtiny13, Clock 9.6 MHz (internal), Port Arduino Uno (same as when I upload the ISP sketch), Programmer Arduino as ISP. I upload by clicking "Upload using Programmer".
Arduino Software is 1.6.4, the programmer Arduino is an Uno SMD edition.
I used this programmer and this tutorial for smeezkitty core13. 
I'm trying to upload this sketch:
// Blink sketch to test ATtiny Chips

//       ATMEL ATTINY13 / ARDUINO
//
//                 +-\/-+
// ADC0 (D 5) PB5 1|*   |8 Vcc
// ADC3 (D 3) PB3 2|    |7 PB2 (D 2) ADC1
// ADC2 (D 4) PB4 3|    |6 PB1 (D 1) PWM1
//            GND 4|    |5 PB0 (D 0) PWM0
//                 +----+


const int LED_PIN = 4; // digital pin
const int DELAY_TIME = 1000; // time between blinks [ms]

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, LOW);
  delay(DELAY_TIME);
  digitalWrite(LED_PIN, HIGH);
  delay(DELAY_TIME);
}

Trying to burn a bootloader with the same settings as uploading to the tiny and then tools -> burn bootloader, get's me the error: 
"efuse" memory type not defined for part "ATtiny13"
Error while burning bootloader.

Skimming through the data sheet I noticed that the tiny13 - 20PU (the 20) stand for 20 MHz,... theoretically one should be able to downclock them to the ordinary 10 MHz, but maybe this is my problem?

user2902: There was some mistakes in the boards.txt it seems. After finding a very detailed and extensive boards file here, I modified it to have neat and tidy categories and is easier to use to become a working boards.txt. I had to burn the bootloader once to set the fuses right. After that everything works like a charm for 3 ATtiny13! No warnings or errors. This is used with Arduino 1.6.4. The folder tree is ~Arduino/hardware/attiny/avr/cores/core13 and ~Arduino/hardware/attiny/avr/boards.txt
# boards.txt for Arduino 1.6.4

menu.flag=GCC Flags
menu.cpu=Processor
menu.clock=Clock

attiny13.name=ATtiny13
attiny13.upload.tool=arduino:avrdude
attiny13.upload.using=arduino:usbtiny

attiny13.bootloader.tool=arduino:avrdude

attiny13.menu.cpu.attiny13=ATtiny13
attiny13.menu.cpu.attiny13.upload.maximum_size=1024
attiny13.menu.cpu.attiny13.upload.maximum_data_size=64
attiny13.menu.cpu.attiny13.build.mcu=attiny13
attiny13.menu.cpu.attiny13.build.core=core13
# attiny13.menu.cpu.attiny13.build.variant=core13

#################################################
############## clock speeds #####################
#################################################

#### 9.6 MHz
############
attiny13.menu.clock.t13_9M6=9.6MHz (internal clock, Preserve EEPROM, BOD disable)
attiny13.menu.clock.t13_9M6.bootloader.low_fuses=0x3A
attiny13.menu.clock.t13_9M6.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_9M6.upload.speed=57600L
attiny13.menu.clock.t13_9M6.build.f_cpu=9600000L

#### 9.6 MHz - 2.7V
attiny13.menu.clock.t13_9M6_bod=9.6MHz (internal clock, Preserve EEPROM, BOD - 2.7V)
attiny13.menu.clock.t13_9M6_bod.bootloader.low_fuses=0x32
attiny13.menu.clock.t13_9M6_bod.bootloader.high_fuses=0xFB
attiny13.menu.clock.t13_9M6_bod.upload.speed=57600L
attiny13.menu.clock.t13_9M6_bod.build.f_cpu=9600000L

#### 4.8 MHz - 2.7V
attiny13.menu.clock.t13_4M8_bod=4.8 MHz (int 4.8 MHz clock, Preserve_EEPROM, BOD - 2.7V)
attiny13.menu.clock.t13_4M8_bod.bootloader.low_fuses=0x31
attiny13.menu.clock.t13_4M8_bod.bootloader.high_fuses=0xFB
attiny13.menu.clock.t13_4M8_bod.upload.speed=57600L
attiny13.menu.clock.t13_4M8_bod.build.f_cpu=4800000L

#### 1.2 MHz
attiny13.menu.clock.t13_1M2=1.2 MHz (int 9.6 MHz divided by 8,Preserve_EEPROM, BOD - 2.7V)
attiny13.menu.clock.t13_1M2.bootloader.low_fuses=0x2A
attiny13.menu.clock.t13_1M2.bootloader.high_fuses=0xFB
attiny13.menu.clock.t13_1M2.upload.speed=9600L
attiny13.menu.clock.t13_1M2.build.f_cpu=1200000L

#### 600 kHz
attiny13.menu.clock.t13_0M6=600 kHz (int 4.8 MHz divided by 8, Preserve_EEPROM, BOD disable)
attiny13.menu.clock.t13_0M6.bootloader.low_fuses=0x29
attiny13.menu.clock.t13_0M6.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_0M6.upload.speed=9600L
attiny13.menu.clock.t13_0M6.build.f_cpu=600000L

## 128 kHz
attiny13.menu.clock.t13_128k=128 KHz (internal watchdog oscillator)
attiny13.menu.clock.t13_128k.bootloader.low_fuses=0x7B
attiny13.menu.clock.t13_128k.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_128k.upload.speed=250
attiny13.menu.clock.t13_128k.build.f_cpu=128000L

## 16 kHz
attiny13.menu.clock.t13_16k=16 KHz (internal watchdog oscillator, Preserve_EEPROM, BOD disable)
attiny13.menu.clock.t13_16k.bootloader.low_fuses=0x2B
attiny13.menu.clock.t13_16k.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_16k.upload.speed=250
attiny13.menu.clock.t13_16k.build.f_cpu=16000L



##-----------------------------------
##--------- compiler flags ----------
##-----------------------------------

attiny13.menu.flag.Os=Default
attiny13.menu.flag.Os.compiler.c.extra_flags=
attiny13.menu.flag.Os.compiler.c.elf.extra_flags=
attiny13.menu.flag.Os.compiler.cpp.extra_flags=

attiny13.menu.flag.Os_flto=Default -flto
attiny13.menu.flag.Os_flto.compiler.c.extra_flags=-Wextra -flto
attiny13.menu.flag.Os_flto.compiler.c.elf.extra_flags=-w -flto
attiny13.menu.flag.Os_flto.compiler.cpp.extra_flags=-Wextra -flto

attiny13.menu.flag.O1=-O1
attiny13.menu.flag.O1.compiler.c.extra_flags=-O1
attiny13.menu.flag.O1.compiler.c.elf.extra_flags=-O1
attiny13.menu.flag.O1.compiler.cpp.extra_flags=-O1

attiny13.menu.flag.O1_flto=-O1 -flto
attiny13.menu.flag.O1_flto.compiler.c.extra_flags=-O1 -Wextra -flto
attiny13.menu.flag.O1_flto.compiler.c.elf.extra_flags=-O1 -w -flto
attiny13.menu.flag.O1_flto.compiler.cpp.extra_flags=-O1 -Wextra -flto

attiny13.menu.flag.O3=-O3
attiny13.menu.flag.O3.compiler.c.extra_flags=-O3
attiny13.menu.flag.O3.compiler.c.elf.extra_flags=-O3
attiny13.menu.flag.O3.compiler.cpp.extra_flags=-O3

attiny13.menu.flag.O3_flto=-O3 -flto
attiny13.menu.flag.O3_flto.compiler.c.extra_flags=-O3 -Wextra -flto
attiny13.menu.flag.O3_flto.compiler.c.elf.extra_flags=-O3 -w -flto
attiny13.menu.flag.O3_flto.compiler.cpp.extra_flags=-O3 -Wextra -flto


2902: <p>I'm trying to program my ATtiny 13 - 20PU. An it seems to work, but there is no action upon the "delay" command. If on the sketch below I comment out the "High" line, my led is off all the time and whenever I have a <code>Pin 4 High</code>, it's on all the time! Basically this seems to be a frequency/fuse/bootloader problem and made me think the upload was broken.</p>

<p>I added a led between the tiny's pin 3 (digital pin 4) and ground with a 1k current limiting resistor. This one is for testing with the attached sketch.
I also tried <a href="http://highlowtech.org/?p=1706" rel="nofollow">this breadboard circuit</a>, which gives exactly the same results.</p>

<p>Upon upload to the tiny I get this:</p>

<pre><code>Sketch uses 380 bytes (37%) of program storage space. Maximum is 1,024 bytes.
Global variables use 8 bytes of dynamic memory.
</code></pre>

<p>(Everybody warns about 2 errors occuring upon a proper upload - I don't get those).</p>

<p>My boards.txt look like this:</p>

<pre><code>menu.cpu=Processor
menu.clock=Clock

attiny.name=ATtiny
attiny.bootloader.tool=arduino:avrdude
attiny.bootloader.unlock_bits=0xff
attiny.bootloader.lock_bits=0xff
attiny.build.core=arduino:arduino
attiny.build.board=attiny
attiny.upload.tool=arduino:avrdude

attiny.menu.cpu.attiny45=ATtiny45
attiny.menu.cpu.attiny45.upload.maximum_size=4096
attiny.menu.cpu.attiny45.build.mcu=attiny45
attiny.menu.cpu.attiny45.build.variant=tiny8

attiny.menu.cpu.attiny85=ATtiny85
attiny.menu.cpu.attiny85.upload.maximum_size=8192
attiny.menu.cpu.attiny85.build.mcu=attiny85
attiny.menu.cpu.attiny85.build.variant=tiny8

attiny.menu.cpu.attiny44=ATtiny44
attiny.menu.cpu.attiny44.upload.maximum_size=4096
attiny.menu.cpu.attiny44.build.mcu=attiny44
attiny.menu.cpu.attiny44.build.variant=tiny14

attiny.menu.cpu.attiny84=ATtiny84
attiny.menu.cpu.attiny84.upload.maximum_size=8192
attiny.menu.cpu.attiny84.build.mcu=attiny84
attiny.menu.cpu.attiny84.build.variant=tiny14

attiny.menu.clock.internal1=1 MHz (internal)
attiny.menu.clock.internal1.bootloader.low_fuses=0x62
attiny.menu.clock.internal1.bootloader.high_fuses=0xdf
attiny.menu.clock.internal1.bootloader.extended_fuses=0xff
attiny.menu.clock.internal1.build.f_cpu=1000000L

attiny.menu.clock.internal8=8 MHz (internal)
attiny.menu.clock.internal8.bootloader.low_fuses=0xe2
attiny.menu.clock.internal8.bootloader.high_fuses=0xdf
attiny.menu.clock.internal8.bootloader.extended_fuses=0xff
attiny.menu.clock.internal8.build.f_cpu=8000000L

attiny.menu.clock.external8=8 MHz (external)
attiny.menu.clock.external8.bootloader.low_fuses=0xfe
attiny.menu.clock.external8.bootloader.high_fuses=0xdf
attiny.menu.clock.external8.bootloader.extended_fuses=0xff
attiny.menu.clock.external8.build.f_cpu=8000000L

attiny.menu.clock.external16=16 MHz (external)
attiny.menu.clock.external16.bootloader.low_fuses=0xfe
attiny.menu.clock.external16.bootloader.high_fuses=0xdf
attiny.menu.clock.external16.bootloader.extended_fuses=0xff
attiny.menu.clock.external16.build.f_cpu=16000000L

attiny.menu.clock.external20=20 MHz (external)
attiny.menu.clock.external20.bootloader.low_fuses=0xfe
attiny.menu.clock.external20.bootloader.high_fuses=0xdf
attiny.menu.clock.external20.bootloader.extended_fuses=0xff
attiny.menu.clock.external20.build.f_cpu=20000000L


#################################################
attiny.menu.cpu.attiny13=ATtiny13
attiny.menu.cpu.attiny13.upload.maximum_size=1024
attiny.menu.cpu.attiny13.build.mcu=attiny13
attiny.menu.cpu.attiny13.build.variant=core13

attiny.menu.clock.internal96=9.6MHz (internal)
attiny.menu.clock.internal96.bootloader.low_fuses=0x7A
attiny.menu.clock.internal96.bootloader.high_fuses=0xff
attiny.menu.clock.internal96.build.f_cpu=9600000L
################################################

attiny.menu.clock.internal48=4.8MHz (internal)
attiny.menu.clock.internal48.bootloader.low_fuses=0x79
attiny.menu.clock.internal48.bootloader.high_fuses=0xff
attiny.menu.clock.internal48.build.f_cpu=4800000L
################################################
</code></pre>

<p>And I choose the settings: Board ATtiny, Processor ATtiny13, Clock 9.6 MHz (internal), Port Arduino Uno (same as when I upload the ISP sketch), Programmer Arduino as ISP. I upload by clicking "Upload using Programmer".</p>

<p>Arduino Software is 1.6.4, the programmer Arduino is an Uno SMD edition.
I used this <a href="https://arduinodiy.wordpress.com/2015/03/31/1256/#comment-907" rel="nofollow">programmer</a> and this <a href="https://arduinodiy.wordpress.com/2015/04/26/installing-attiny13-core-files-in-arduino-ide-1-6-x-and-1-7-x/" rel="nofollow">tutorial</a> for smeezkitty core13. </p>

<p>I'm trying to upload this sketch:</p>

<pre><code>// Blink sketch to test ATtiny Chips

//       ATMEL ATTINY13 / ARDUINO
//
//                 +-\/-+
// ADC0 (D 5) PB5 1|*   |8 Vcc
// ADC3 (D 3) PB3 2|    |7 PB2 (D 2) ADC1
// ADC2 (D 4) PB4 3|    |6 PB1 (D 1) PWM1
//            GND 4|    |5 PB0 (D 0) PWM0
//                 +----+


const int LED_PIN = 4; // digital pin
const int DELAY_TIME = 1000; // time between blinks [ms]

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_PIN, LOW);
  delay(DELAY_TIME);
  digitalWrite(LED_PIN, HIGH);
  delay(DELAY_TIME);
}
</code></pre>

<p>Trying to burn a bootloader with the same settings as uploading to the tiny and then tools -> burn bootloader, get's me the error: </p>

<pre><code>"efuse" memory type not defined for part "ATtiny13"
Error while burning bootloader.
</code></pre>

<p>Skimming through the data sheet I noticed that the tiny13 - 20PU (the 20) stand for 20 MHz,... theoretically one should be able to downclock them to the ordinary 10 MHz, but maybe this is my problem?</p>
 2902: <p>There was some mistakes in the boards.txt it seems. After finding a very detailed and extensive boards file <a href="http://forum.arduino.cc/index.php?topic=89781.msg2235877#msg2235877" rel="nofollow">here</a>, I modified it to have neat and tidy categories and is easier to use to become a working boards.txt. I had to burn the bootloader once to set the fuses right. After that everything works like a charm for 3 ATtiny13! No warnings or errors. This is used with Arduino 1.6.4. The folder tree is <code>~Arduino/hardware/attiny/avr/cores/core13</code> and <code>~Arduino/hardware/attiny/avr/boards.txt</code></p>

<pre><code># boards.txt for Arduino 1.6.4

menu.flag=GCC Flags
menu.cpu=Processor
menu.clock=Clock

attiny13.name=ATtiny13
attiny13.upload.tool=arduino:avrdude
attiny13.upload.using=arduino:usbtiny

attiny13.bootloader.tool=arduino:avrdude

attiny13.menu.cpu.attiny13=ATtiny13
attiny13.menu.cpu.attiny13.upload.maximum_size=1024
attiny13.menu.cpu.attiny13.upload.maximum_data_size=64
attiny13.menu.cpu.attiny13.build.mcu=attiny13
attiny13.menu.cpu.attiny13.build.core=core13
# attiny13.menu.cpu.attiny13.build.variant=core13

#################################################
############## clock speeds #####################
#################################################

#### 9.6 MHz
############
attiny13.menu.clock.t13_9M6=9.6MHz (internal clock, Preserve EEPROM, BOD disable)
attiny13.menu.clock.t13_9M6.bootloader.low_fuses=0x3A
attiny13.menu.clock.t13_9M6.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_9M6.upload.speed=57600L
attiny13.menu.clock.t13_9M6.build.f_cpu=9600000L

#### 9.6 MHz - 2.7V
attiny13.menu.clock.t13_9M6_bod=9.6MHz (internal clock, Preserve EEPROM, BOD - 2.7V)
attiny13.menu.clock.t13_9M6_bod.bootloader.low_fuses=0x32
attiny13.menu.clock.t13_9M6_bod.bootloader.high_fuses=0xFB
attiny13.menu.clock.t13_9M6_bod.upload.speed=57600L
attiny13.menu.clock.t13_9M6_bod.build.f_cpu=9600000L

#### 4.8 MHz - 2.7V
attiny13.menu.clock.t13_4M8_bod=4.8 MHz (int 4.8 MHz clock, Preserve_EEPROM, BOD - 2.7V)
attiny13.menu.clock.t13_4M8_bod.bootloader.low_fuses=0x31
attiny13.menu.clock.t13_4M8_bod.bootloader.high_fuses=0xFB
attiny13.menu.clock.t13_4M8_bod.upload.speed=57600L
attiny13.menu.clock.t13_4M8_bod.build.f_cpu=4800000L

#### 1.2 MHz
attiny13.menu.clock.t13_1M2=1.2 MHz (int 9.6 MHz divided by 8,Preserve_EEPROM, BOD - 2.7V)
attiny13.menu.clock.t13_1M2.bootloader.low_fuses=0x2A
attiny13.menu.clock.t13_1M2.bootloader.high_fuses=0xFB
attiny13.menu.clock.t13_1M2.upload.speed=9600L
attiny13.menu.clock.t13_1M2.build.f_cpu=1200000L

#### 600 kHz
attiny13.menu.clock.t13_0M6=600 kHz (int 4.8 MHz divided by 8, Preserve_EEPROM, BOD disable)
attiny13.menu.clock.t13_0M6.bootloader.low_fuses=0x29
attiny13.menu.clock.t13_0M6.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_0M6.upload.speed=9600L
attiny13.menu.clock.t13_0M6.build.f_cpu=600000L

## 128 kHz
attiny13.menu.clock.t13_128k=128 KHz (internal watchdog oscillator)
attiny13.menu.clock.t13_128k.bootloader.low_fuses=0x7B
attiny13.menu.clock.t13_128k.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_128k.upload.speed=250
attiny13.menu.clock.t13_128k.build.f_cpu=128000L

## 16 kHz
attiny13.menu.clock.t13_16k=16 KHz (internal watchdog oscillator, Preserve_EEPROM, BOD disable)
attiny13.menu.clock.t13_16k.bootloader.low_fuses=0x2B
attiny13.menu.clock.t13_16k.bootloader.high_fuses=0xFF
attiny13.menu.clock.t13_16k.upload.speed=250
attiny13.menu.clock.t13_16k.build.f_cpu=16000L



##-----------------------------------
##--------- compiler flags ----------
##-----------------------------------

attiny13.menu.flag.Os=Default
attiny13.menu.flag.Os.compiler.c.extra_flags=
attiny13.menu.flag.Os.compiler.c.elf.extra_flags=
attiny13.menu.flag.Os.compiler.cpp.extra_flags=

attiny13.menu.flag.Os_flto=Default -flto
attiny13.menu.flag.Os_flto.compiler.c.extra_flags=-Wextra -flto
attiny13.menu.flag.Os_flto.compiler.c.elf.extra_flags=-w -flto
attiny13.menu.flag.Os_flto.compiler.cpp.extra_flags=-Wextra -flto

attiny13.menu.flag.O1=-O1
attiny13.menu.flag.O1.compiler.c.extra_flags=-O1
attiny13.menu.flag.O1.compiler.c.elf.extra_flags=-O1
attiny13.menu.flag.O1.compiler.cpp.extra_flags=-O1

attiny13.menu.flag.O1_flto=-O1 -flto
attiny13.menu.flag.O1_flto.compiler.c.extra_flags=-O1 -Wextra -flto
attiny13.menu.flag.O1_flto.compiler.c.elf.extra_flags=-O1 -w -flto
attiny13.menu.flag.O1_flto.compiler.cpp.extra_flags=-O1 -Wextra -flto

attiny13.menu.flag.O3=-O3
attiny13.menu.flag.O3.compiler.c.extra_flags=-O3
attiny13.menu.flag.O3.compiler.c.elf.extra_flags=-O3
attiny13.menu.flag.O3.compiler.cpp.extra_flags=-O3

attiny13.menu.flag.O3_flto=-O3 -flto
attiny13.menu.flag.O3_flto.compiler.c.extra_flags=-O3 -Wextra -flto
attiny13.menu.flag.O3_flto.compiler.c.elf.extra_flags=-O3 -w -flto
attiny13.menu.flag.O3_flto.compiler.cpp.extra_flags=-O3 -Wextra -flto
</code></pre>
