DMA Controller: How Peripheral Devices Transfer Data to RAM a basic computer consists of three parts: a central processing unit (CPU), memory (RAM), and a bus that allows data transfer between them. all other connected hardware is considered peripheral devices. In this video, I explain how DMA works in a modern computer architecture, including: the problem with transferring data between peripheral devices and main memory (RAM), how DMA controllers solve this problem, types of DMA architectures, how modern PCI Express (PCIe) systems integrate DMA controllers, and the role of the I/O MMU in translating virtual addresses to physical addresses when device data transfer is needed. SUMMARY hardware devices need to read or write data to the main memory from time to time. Since it requires a processor to move each piece of data from one place to another, it puts a lot of pressure on the CPU and prevents it from doing its job - running programs. that's why computers use Direct Memory Access Controllers (DMA Controllers). DMA Controllers are specialized hardware that transfers data from a peripheral device to main memory (and vice versa) with almost no intervention from the processor. DMAC hardware can be organized as a Centralized DMA (First Party DMA) or use Bus Mastering (Third Party DMA) as the data transfer management method. In modern PCI Express (PCIe) based systems, each device must have its own internal DMA Controller so it can transfer data independently of the rest of the system. Peripheral devices use the I/O Memory Management Unit (IOMMU) to translate virtual addresses to physical ones to access the correct memory locations in RAM. LINKS 📚 Computer Memory and Architecture E-Book Collection: 📚 Inside the Core: How the CPU Works (E-Book): 📚 Interrupts in Modern Computer Systems (E-Book): 📚 The Anatomy of Virtual Memory (E-Book): 📚 Beginner's Guide to CPU Caches (E-Book): ❤ Support my work: SOURCES The information in this video is partially based on the book 'Operating System Concepts' (10th Edition) by Abraham Silberschatz, Peter B. Galvin, and Greg Gagne. TABLE OF CONTENTS 00:00 Basic Parts of a Computer 00:45 The Peripheral Data Transfer Problem 01:36 Introduction to DMA Controllers 02:27 Centralized DMAC / Third-Party DMA 03:22 Bus Mastering / First-Party DMA 03:59 DMAC Operation Modes 05:32 DMAC and CPU Caching 06:08 DMA Controllers in PCI Express Architecture 07:06 Peripheral Devices and Virtual Memory ATTRIBUTIONS Some of the images used in this video were designed by macrovector / / Freepik at #computerscience #memorymanagement #computers #operatingsystem #computerhardware