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Boot Sequence: BIOS vs UEFI

Step from power-on through OS handoff, with toggles for the legacy and modern paths

UEFI firmware boot flowReset VectorSEC PhasePEI PhaseDXE PhaseACPI TablesBDS PhaseOS Loaderphase 1 of 7
Step 1 / 7Reset Vector

Power is applied. The CPU wakes up at a fixed address near the top of memory and fetches its first instruction from SPI flash. There is no RAM yet.

Arrow keys · R to reset · Toggle mode above

Tap dots to jump · Switch UEFI/Legacy above

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