How Linux Detects Physical Memory: Inside the E820 BIOS Interface

This article explains how the Linux kernel discovers physical memory during boot by invoking the BIOS interrupt 0x15 with the E820 function, how firmware (ACPI) provides the memory map, and how the kernel stores, prints, and later manages those memory regions using e820 tables, memblock, and the buddy allocator.

ACPIE820Kernel

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How Linux Detects Physical Memory: Inside the E820 BIOS Interface

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Feb 19, 2025 · Operations

Linux Kernel Memory Detection via E820 Mechanism

This article explains how the Linux kernel detects physical memory during boot by leveraging the E820 mechanism, where firmware reports memory ranges via interrupt 15H, enabling the kernel to map usable memory addresses for subsequent allocation.

Boot ProcessE820Linux kernel

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Linux Kernel Memory Detection via E820 Mechanism