Changing the startup sound on a Power Mac

Changing the startup sound on a Power Mac. When I asked if it was possible, I was told that was impossible . When I searched on the Internet, I found messages indicating that it was impossible. But obviously, Doug Brown has not read the Internet or asked anyone : he just did it. I contacted him, he helped me a little, and I did it, too.
En français.
C36961 FAMILY_LOW

Basically: the Mac startup sound is stored in a ROM (with Open Firmware on old items, the EFI on recent ones). Doug had already changed the startup sound on an old Mac by directly modifying the ROM , but it requires a lot of equipment.

With “New World ROM” Macs, the ROM is to be modified with a software (it can be flashed like a BIOS) and changing the startup sound is possible. Good news for me, Doug used a Power Mac G3 B&W for his trials , and I just have two of these available. It’s easier to have two, for a good reason: as we play with the boot ROM, the risks are to totally crash the machine.

It is simple : Doug sent me the files needed to compile a program that will rebuild a valid ROM with the requested sound. I fumbled a bit to compile and get the correct files (including the sound), but it is functional.

It must be the original firmware (you should probably convert the disk image to open it), Doug’s program and of course a startup sound.

On the Mac, it works on a Power Mac G3 B&W, and a priori on other Power PC “New World” models (since the first iMac), but I do not have enough info to check, or more precisely I do not want to brick my Mac mini.

The preparation of the sound

Open the sound with Audacity.
Pass it on 16-bit , 44 kHz, mono.
Check the duration : no more than 2.5 seconds.
Export it in RAW (File -> Export -> Other uncompressed formats -> RAW / Signed 16 bit PCM).
Pass the file in Big Endian with a command.

dd if=entree.raw of=sortie.raw conv=swab

Now, start the program that will make the modification of the firmware .

Download G3ChimePatcher on Doug’s site, and then compile the program. It runs under Mac OS X and Linux. In my case, it worked on OS X Mavericks.

g++ adler32.cpp inject_chime.cpp ima.cpp md5.cpp ascii85.cpp -o g3chimepatcher

Then go get the firmware file in the archive .smi. Depending on the type of the machine, you may need to convert the image in .dmg before.

Finally, launch the program.

./g3chimepatcher "G3 firmware" sortie.raw "G3 Firmware Mod"

If everything goes well , you will get this answer.

Successfully injected new startup chime.

Now we need a Power Mac G3 B&W on MAc OS 9 , the firware update program, and an effective text editor (in my case , the demo of BBEdit 6.1).

As explained here, you must first update the update program for it to accept a firmware already installed. A line must be replaced by another.

The old line :

Apple PowerMac1,1 1.1f1 BootROM built on 03/08/99 at 13:29:20

The new line :

Apple PowerMac1,1 1.1f4 BootROM built on 04/09/99 at 13:57:32

Then, open the original firmware file with BBEdit and paste in (to be sure to keep the good values) the content of the new firmware.

When done, simply run the update program, follow the instructions and pray. Because if you ever poorly constructed file, the Mac will be bricked. I took the risk for one simple reason : I have two Power Mac G3 B&W at home.

When this is done, you may have a message when booting Mac OS 9 which indicates that the upgrade did not work. This is normal : just launch the original version of the update program, which will clear the message on the next startup .

A video with the two sounds tested: the first one is the Wilhelm scream , the second one is the startup sound of the TAM ( Twentieth Anniversary Macintosh). Sorry for the background noise, this is the only way to hear the sound when shooting with an iPhone.