I/O controllers

RP1 is an in-house silicon chip built into later-generation Raspberry Pi computers to manage their peripherals, such as USB, Ethernet, GPIO, and storage interfaces. It complements the main processor by moving high-speed serial interfaces off the more expensive process node.

Unlike Raspberry Pi microcontrollers, RP1 isn’t a standalone chip; it’s an I/O controller built into Raspberry Pi 5 and Compute Module 5. As a built-in I/O controller, RP1 isn’t sold separately but people do write software for it, which is why it’s described here.

Note
 RP1 isn’t short for the first Raspberry Pi single-board computer (Raspberry Pi Model B).

RP1 overview

RP1 measures approximately 12 x 12 mm in a BGA package with 0.65 mm pin spacing. It connects to the main CPU (BCM2712) on a Raspberry Pi 5 and Compute Module 5 over a PCIe 2.0 x4 link, and handles most external I/O.

RP1 complements the main processor by managing peripherals and offloading I/O tasks from the main CPU. This continues Raspberry Pi’s traditional two-chip architecture where the CPU manages core processing and a companion chip (in this case, RP1) manages peripherals. For more information, see Peripheral interfaces.

RP1 also integrates several internal system components to support high-performance, low-latency I/O operation. For more information, see Internal features.

RP1 includes dedicated multimedia and audio hardware to support display outputs, cameras, and basic audio functionality. For more information, see Multimedia and audio components.

Peripheral interfaces

RPI provides the following peripheral interfaces:

  • 4-lane PCIe 2.0 endpoint

  • Gigabit Ethernet MAC

  • Two USB host controllers (providing more than twice the usable USB bandwidth compared to Raspberry Pi 4), each with:

    • One USB 3.0 port

    • One USB 2.0 port

  • Two SDIO/eMMC interfaces (not used on Raspberry Pi 5)

  • Two 4-lane MIPI transceivers supporting DSI and CSI-2 for display and camera interfaces

  • Low-speed peripherals, including:

    • SPI

    • UART

    • I2C

    • PWM

    • GPIO

    • I2S

Internal features

RP1 integrates the following internal system components:

  • Two Cortex M3 processors with tightly-coupled memories

  • An 8-channel DMA controller

  • Multiple PLLs

  • A 12-bit ADC with temperature sensor

  • 64 kB shared SRAM

  • Timing generator

Multimedia and audio components

RP1 includes the following multimedia and audio blocks for video output and simple audio generation without external codecs:

  • Video DAC (3-channel, supporting PAL/NTSC and VGA; only one composite channel used on Raspberry Pi 5).

  • DPI video frame generator for displays connected to GPIO pins.

  • CSI-2 receiver, DMA and ISP front-end for framing and statistics generation for cameras connected to the MIPI ports.

  • DSI DMA and transmitter for displays connected to the MIPI ports.

  • Delta-sigma PWM audio out.

  • PDM microphone clock generator and stereo bitstream input.

RP1 naming

Raspberry Pi silicon chips follow a naming convention that starts with RP to refer to 'Raspberry Pi', followed by a number. The number in the I/O controller refers to the chip’s generation, being the first embedded I/O controller chip.