What I've read from UEFI so far is that it has features that BIOS didn't have: it can look in the filesystem and find the boot loader there.
Then, since the UEFI boot system can read directly
C:\Windows\System32\winload.efifrom the main partition for C:\, why is there the need for a separate 100 MB partition when it could just read winload.efi directly in the main partition?
Can't the GPT link that it should use C:\Windows\System32\winload.efi and avoid the 100 MB partition?
(illustrative image, not taken from my system, thus the different partition sizes)
02 Answers
UEFI doesn't support NTFS. The spec calls for FAT family support. Vendors could add NTFS support, but:
- It's not really necessary, because FAT32 is completely sufficient and much less complex
- Unless all vendors agreed to add NTFS support, it wouldn't be a universally usable configuration anyway.
EFI System Partition isn't tied to any particular OS. If you're multibooting, you can store multiple bootloaders on a single partition.
In addition to gronostaj's answer there's another feature that require a separate partition: full disk encryption, aka BitLocker in Microsoft world.
From Microsoft documentation:
BitLocker Drive Encryption Partitioning Requirements
BitLocker must use a system partition that is separate from the Windows partition. The system partition:
- Must be configured as the active partition.
- Must not be encrypted or used to store user files.
- Must have at least 100 megabytes (MB) of space.
- Must have at least 50 MB of free space.
- May be shared with a recovery partition.
The unencrypted partition contains the info needed to read the encrypted partition, and the UEFI can't access this encrypted partition.
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