Direct Memory Access (DMA) allows peripherals to read/write memory without CPU intervention, improving performance and reducing CPU load.

• ESP8266: Does not have DMA support. All peripheral transfers (UART, SPI, I²C, ADC, etc.) are handled by the CPU. This limits maximum throughput and increases CPU usage for high-speed data operations.
• ESP32: Fully supports DMA for several peripherals including SPI, I²S, and UART. DMA allows high-speed data transfers directly to/from memory, enabling efficient audio streaming, high-speed SPI devices, and other data-intensive applications.

Summary: If your project requires high-speed peripheral data transfer with minimal CPU involvement, the ESP32 is the preferred choice. The ESP8266 can still handle high-speed tasks but relies entirely on CPU cycles, which can become a bottleneck.