July, 2024

Understanding Low-Level Principles – Memory Series | S06 | How DDR5 Doubles Memory Bandwidth Compared to DDR4 Key Insight: Every new generation of memory standard is essentially bargaining with the laws of physics — when bandwidth is insufficient, find a new way to “squeeze” more data through. 1. The Bandwidth Improvement Formula Memory bandwidth calculation... » read more

# A06 — new/delete 和 malloc/free: C++ memory management的Difference **金句**: new 不是 malloc, delete 不是 free — 它们不只是allocate, 还有构造和析构. — ## new 和 malloc 的Essential Difference “` new 和 malloc 的区别： malloc： – C 库函数 – 只分配内存，不初始化 – 返回 void* – 失败返回 NULL new： – C++ 关键字 – 分配内存 + 调用构造函数 – 返回具体类型的指针（不需要类型转换） – 失败抛出... » read more

330 – Deep Dive into Android Boot Process: From Power-On to the First App Series Navigation: 331-Bootloader | 332-init Process | 333-Zygote Have you ever thought about this: From the moment you press the power button until the desktop wallpaper appears on screen, what does the Android system go through? This is a complete chain... » read more

H04 — XMP and EXPO: How Memory Overclocking Works, and Why a 3200-rated Stick Can Run at 3600 Key Insight: Bought a 3200-rated stick, runs at 3600. It’s not magic; it’s engineering. Why Memory Has Both JEDEC and XMP Frequencies When buying memory, you see DDR4-3200 on the specs, but you can actually set it... » read more

# Writing an OS Kernel from Scratch – Part 33: e1000 NIC Driver — Connect Your OS to the Network World! “An operating system without a network is just an information island. Today, we implement the Intel e1000 NIC driver, letting MyOS ping the outside world!” In previous chapters, we built a complete desktop system:... » read more

K11 — The Full Path of Physical Page Allocation: alloc_pages and the Buddy System Key Insight: Every call to alloc_pages embarks on a complete journey from request to physical page frame. The alloc_pages Function Signature alloc_pages is the core function for allocating physical pages in Linux: struct page *alloc_pages(gfp_t gfp_mask, unsigned int order); Parameters: -... » read more

title: [Writing an OS Kernel from Scratch] 335 – ARM Architecture Boot: From Power-On to Kernel category: os tag: [arm, boot, embedded, u-boot] source: https://github.com/golang12306/os-kernel-from-scratch [Writing an OS Kernel from Scratch] 335 – ARM Architecture Boot: From Power-On to Kernel 1. ARM Boot Sequence Overview Embedded device boot is a layered relay race. To understand... » read more

Writing an OS Kernel from Scratch | 347: Display — From Framebuffer to GPU Abstract: The display is the most intuitive output device of a computer, but the timing, resolution, framebuffer, and GPU rendering pipeline behind it are rarely studied in depth. This article starts from CRT timing principles, explains the DRM/KMS architecture, modetest/xrandr commands,... » read more

B10 — Why fork is Fast: The Copy-On-Write Mechanism Key Insight: Don’t copy, just share. Until it’s actually needed. The Traditional Problem with fork: Massive Memory Copying The fork system call creates a new process. The traditional implementation copies the entire memory space of the parent process: 传统 fork 的问题： 父进程内存：假设 1GB fork() 执行时： -... » read more

K06 — The Full Flow of mmap Memory Allocation: Demand Paging and Physical Page Allocation Key Insight: When you request 1 GB of memory, the system does not actually give you 1 GB upfront. It only allocates when you actually use it. Lazy Allocation in mmap mmap only creates virtual address mappings. It does not... » read more