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No RAM installed/detected Three successive tones followed by a repeating five-second pause: Incompatible RAM types; No good banks One long tone while the power button is held down: EFI ROM update in progress (For Macs made until 2012) Three long tones, three short tones, three long tones: EFI ROM corruption detected, ROM recovery in process
Device configuration overlay (DCO) is a hidden area on many of today's hard disk drives (HDDs). Usually when information is stored in either the DCO or host protected area (HPA), it is not accessible by the BIOS (or UEFI), OS, or the user. However, certain tools can be used to modify the HPA or DCO.
If the sector is read successfully, some BIOSes will also check for the boot sector signature 0x55 0xAA in the last two bytes of the sector (which is 512 bytes long), before accepting a boot sector and considering the device bootable. [b] When a bootable device is found, the BIOS transfers control to the loaded sector.
Furthermore, the Linux kernel can be compiled with the option to run as an EFI bootloader on its own through the EFI boot stub feature. HP-UX has used (U)EFI as its boot mechanism on IA-64 systems since 2002. OpenVMS has used EFI on IA-64 since its initial evaluation release in December 2003, and for production releases since January 2005. [121]
After restarting, it shows a message for a few seconds informing the user that a problem caused the computer to restart, before continuing to boot. The message now includes a Chinese translation. If five new kernel panics occur within three minutes of the first one, the Mac will display a prohibitory sign for thirty seconds, and then shut down ...
On Apple Mac computers using Intel x86-64 processor architecture, the EFI system partition is initially left blank and unused for booting into macOS. [13] [14]However, the EFI system partition is used as a staging area for firmware updates [15] and for the Microsoft Windows bootloader for Mac computers configured to boot into a Windows partition using Boot Camp.
In this example of dual booting, the user chooses by inserting or removing the DVD from the computer, but it is more common to choose which operating system to boot by selecting from a boot manager menu on the selected device, by using the computer keyboard to select from a BIOS or UEFI Boot Menu, or both; the Boot Menu is typically entered by ...
A modern PC is configured to attempt to boot from various devices in a certain order. If a computer is not booting from the device desired, such as the floppy drive, the user may have to enter the BIOS Setup function by pressing a special key when the computer is first turned on (such as Delete, F1, F2, F10 or F12), and then changing the boot order. [6]