September, 2024

Writing an OS Kernel from Scratch | Windows MBR+BIOS Boot: What Happens Before BOOTMGR and How to Fix It Have you noticed a phenomenon: You assemble a computer, install Windows 10, the System Reserved partition takes up 100MB, and the C: drive takes everything else. This 100MB partition is usually invisible in File Explorer. Only... » read more

Writing an OS Kernel from Scratch | Interrupt and Exception Handling — How the CPU Gets “Interrupted” by Peripherals Your program is running, and suddenly you press a key on the keyboard — how does the operating system know about it? How does the CPU instantly switch from executing code to handling keyboard input? The... » read more

B04 — From Real Mode to Protected Mode: GDT and CR0 Setup Key Insight: Protected mode doesn’t “protect” memory. It allows the CPU to manage more complex memory access rules. Limitations of Real Mode After reset, the CPU defaults to Real Mode, the operating mode from the 8086 era. Real Mode has two severe limitations:... » read more

Writing an OS Kernel from Scratch | Audio Subsystem — How ALSA Plays Sound Have you ever wondered about this process: When playing a song, how does the CPU turn digital signals into vibrations from the speaker? From WAV/MP3 files to music in your headphones, there’s sampling rate, bit depth, alsa-lib, the ALSA driver, HDA... » read more

B08 — Memory Layout of Kernel Space and User Space: vmalloc vs kmalloc Key Insight: The division of virtual address space is one of the most important OS design decisions. x86-64 Virtual Address Space Layout Modern Linux uses a 48-bit virtual address space. User space and kernel space each have separate regions: x86-64 虚拟地址空间布局： 0x0000000000000000... » read more

title: [Writing an OS Kernel from Scratch] 337 – DRAM Training: From Principles to Debugging category: os tag: [dram, ddr, embedded, signal-integrity] source: https://github.com/golang12306/os-kernel-from-scratch [Writing an OS Kernel from Scratch] 337 – DRAM Training: From Principles to Debugging 1. What Is DRAM Training? DRAM Training is the process where the DDR controller automatically adjusts signal... » read more

Writing an OS Kernel from Scratch | Virtual Memory — The Complete Journey of Paging and Linear Addresses You write int *p = (int*)0x00401000; *p = 42; — is this address a real physical address? How does the operating system ensure every process feels it has 4GB of memory when there’s actually only 8GB of... » read more

H01 — How Memory Modules Plug Into the Motherboard: DIMM Structure and Socket Design Key Insight: Behind every visible interface lie countless electrical conventions. DIMM Full Name and Basic Concepts DIMM = Dual Inline Memory Module. DIMM vs SIMM： SIMM（Single Inline Memory Module）： - 单面引脚（只能接触一侧的触点） - 72-pin 或 30-pin（早期） - 只能提供 32-bit 或 16-bit 数据宽度... » read more