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Diffstat (limited to 'documentation/UEFI general/UEFI Overview')
| -rw-r--r-- | documentation/UEFI general/UEFI Overview | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/documentation/UEFI general/UEFI Overview b/documentation/UEFI general/UEFI Overview new file mode 100644 index 0000000..f173bfb --- /dev/null +++ b/documentation/UEFI general/UEFI Overview @@ -0,0 +1,20 @@ +Reference: https://wiki.osdev.org/UEFI + + +UEFI VS LEGACY BIOS + +Both motherboards come with BIOS ROMs, which contains firmware that performs the initial power-on configuration of the +system before loading some third-party code into memory and jumping to it. +Differences: + - where they find that code + - how to prepare system before jumping to it + - what convenience functions they provide for the code to call while running + +PLATFORM INITIALIZATION + +BIOS: performs all the usual platform initialization (memory controller configuration, PCI bus configuration and BAR mapping, + graphics card initialization, etc...) but then drops into a backwards-compatible real mode environment. + Bootloader must enable A20 gate, configure a GDT and an IDT, switch to protected mode, and for x86-64 CPUs, + configure paging and switch to long mode. +UEFI firmware: performs those same steps but also prepares a protected mode environment with flat segmentation and for x86-64 CPUs, + a long mode environment with identity-mapped paging. The A20 gate is enabled as well. |