How to Get Into the BIOS in a Mac Computer

By Brian Cleary

Enter Open Firmware to access the Mac's booting firmware.
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Mac computers are a popular addition to small businesses given their power, reliability and customer service. When dealing with peripheral devices that many small businesses have, you may need to access the Mac's booting firmware, known as the BIOS on Windows machines. Apple's booting firmware, Open Firmware, is first accessed on startup and provides a place to do diagnostics and troubleshooting on the computer. Since Open Firmware controls the computer's boot process, care should be taken altering the settings in this area.

Power off the computer. Open Firmware can only be accessed by starting the computer fresh and preventing the operating system from loading.

Power up the computer and hold down the "Command," "Option," "0" and "F" keys at the same time while booting.

Look for the "Ok" prompt which means the Mac is operating normally and ready for the user's commands.

Enter the commands in the prompt to access the boot configuration modules. Some of these commands are "dev /memory" for RAM configurations, "dev /ls" for the device tree and "dev /cpus" for CPU information.