Ja, jag förstår att du sökt på Apple, men i alla fall.
Har du provat detta? Bortse från version nummer i instruktionen...
Note: If a message says your firmware is up-to-date with version 4.1.7 of the iMac Firmware Updater, or that this version of the iMac Firmware Updater will not run on this computer, then you do not need this update. If a message says you need to install Mac OS 9.1, the firmware updater will not run until you install Mac OS 9.1 or later.
2. Follow the onscreen instructions. When prompted, click Shut Down in the dialog box to shut down your iMac.
3. Locate the programmer´s button on the side of the iMac, to the right of the reset button. Press and
hold in the programmer´s button. You may need to use a pen or a straightened paper clip.
4. While you hold in the programmer´s button, press the Power button to start up your iMac.
5. Continue to hold in the programmer´s button until you hear a long tone.
Release the programmer´s button when you hear the tone. The update starts automatically.