# Choosing a microcontroller or processor

Answer six questions to find the kind of chip that fits your project, from small microcontrollers to Linux-class processors. You get a class, not a brand.

Page: https://dharanova.com/learn/choosing-a-processor · Track: Think · Level: Core · Facts last checked 7 October 2026

Read first: [Microcontroller or microprocessor?](https://dharanova.com/learn/mcu-vs-mpu.md), [Chip, module, SoM, dev board, SBC](https://dharanova.com/learn/chip-som-board.md), [GPUs, DSPs, ISPs, NPUs and what TOPS means](https://dharanova.com/learn/accelerators-and-tops.md)

## Key points

1. Software support often matters more than the silicon. If a chip's drivers are in the main Linux kernel, not only in the vendor's own kernel, it is much easier to keep moving to newer kernels with security fixes. [1]
2. Several chip vendors run longevity programmes that commit, with conditions, to keep making listed parts for a minimum period, often 10 or 15 years, which matters for industrial products with long lives. Check when each vendor starts counting, and read the conditions. (as of 6 October 2026) [2][3]
3. Safety-critical designs follow a functional-safety standard, such as ISO 26262 (road vehicles, ASIL A–D) or the general IEC 61508 (SIL 1–4), and are much easier with parts that come with the vendor's safety documentation. [4][5][6]

## The six questions

1. Does the device need a full operating system? Options: Yes; No; Not sure.
2. How is it powered? Options: Battery, months to years; Rechargeable battery; Mains or USB, always on.
3. Which wireless link must the device have? Options: None, or wired only; Bluetooth LE, Thread or Zigbee; Wi-Fi; Cellular or LoRa.
4. What is the heaviest work it does? Options: Read sensors, switch outputs; Audio or signal processing; Camera AI or large ML models; A rich touchscreen interface or video.
5. Must anything respond within microseconds, every time? Options: Yes; No.
6. Does either of these apply? Options: Neither; Safety-critical (vehicle, medical, machinery); Must stay in production for 10+ years.

## How answers map to a class

Rules are tried in order; the first whose conditions all match decides the class.

1. Does the device need a full operating system? Yes; How is it powered? Battery, months to years → Entry application processor. If it must run Linux on a long-life battery, start with the smallest and most efficient application processors, and plan for it to sleep most of the time.
2. Does the device need a full operating system? Yes or Not sure; What is the heaviest work it does? Camera AI or large ML models; How is it powered? Mains or USB, always on or Rechargeable battery → High-performance application processor. Camera AI or large models need fast cores and a real accelerator, which in practice means Linux. A single camera running a small model may also fit a mainstream part with an NPU.
3. Does the device need a full operating system? Yes; How is it powered? Rechargeable battery; What is the heaviest work it does? Read sensors, switch outputs or Audio or signal processing → Entry application processor. If it must run Linux on a rechargeable battery and the work is light, the smallest and most efficient application processors are the place to start.
4. Does the device need a full operating system? Yes; Must anything respond within microseconds, every time? Yes; What is the heaviest work it does? Read sensors, switch outputs or Audio or signal processing → Entry application processor. Linux plus guaranteed timing points to a processor with a microcontroller core alongside. Many entry parts have one; so do several mainstream parts, if you need more compute.
5. Does the device need a full operating system? Yes → Mainstream application processor. Quad-core application processors are built for Linux devices with displays, and for gateways that serve many smaller devices.
6. What is the heaviest work it does? Camera AI or large ML models or A rich touchscreen interface or video → High-performance microcontroller. Without Linux, camera and touchscreen work is easiest on a fast microcontroller with lots of RAM and, for vision, an NPU. Simple displays can also run on smaller chips.
7. Which wireless link must the device have? Bluetooth LE, Thread or Zigbee or Wi-Fi → Wireless microcontroller. A radio built into the microcontroller is cheaper and smaller than a separate radio chip, and pre-certified modules built around one make certification much easier.
8. Any other answers → General-purpose microcontroller. Most sensing and control jobs fit comfortably in an ordinary microcontroller.

## The six classes of processor

### General-purpose microcontroller

A small, cheap, low-power chip that reads sensors, drives outputs and can run on a battery for years.

- CPU: One or two 8-bit or 32-bit cores (AVR, Cortex-M0+/M4/M33, RISC-V)
- Clock: About 20 MHz to 200 MHz
- Memory: 2 KB to a few hundred KB of SRAM, a few low-power parts reach megabytes; flash (or MRAM) on-chip on most parts
- Software: Bare metal or a small RTOS
- Power: Microamps asleep; under a milliamp to a few tens of milliamps running, depending on clock

Good for: Sensor nodes; Simple controllers and appliances; Learning embedded programming.
Wrong for: Anything that needs Linux; Camera processing; Rich graphical interfaces, apart from a few display-oriented parts.

Example parts:

- Ambiq Apollo4 Plus (chip only): 1× Cortex-M4F at 192 MHz
- Microchip AVR64DD32 (chip only): 1× AVR (8-bit) at 24 MHz
- Raspberry Pi Pico 2 W (board): 2× Cortex-M33 or Hazard3 (RV32), chosen per core at boot at 150 MHz
- Raspberry Pi RP2350 (chip only): 2× Cortex-M33 or Hazard3 (RV32), chosen per core at boot at 150 MHz
- STMicroelectronics STM32U083 (chip only): 1× Cortex-M0+ at 56 MHz
- Texas Instruments MSPM0L1306 (chip only): 1× Cortex-M0+ at 32 MHz
- WCH CH32V003 (chip only): 1× QingKe V2A (RV32EC) at 48 MHz

### Wireless microcontroller

A microcontroller with the radio on the same chip: most often Bluetooth LE, Thread and Zigbee, or Wi-Fi; a few add sub-GHz LoRa or cellular.

- CPU: One or two 32-bit cores (Cortex-M0+/M33, RISC-V, Xtensa), sometimes with a low-power helper core
- Clock: About 48 to 240 MHz
- Memory: Tens to hundreds of KB of SRAM
- Software: Vendor SDK on FreeRTOS or Zephyr
- Power: Microamps asleep; milliamps receiving; Wi-Fi transmit peaks are far higher than Bluetooth LE

Good for: Smart-home devices; Wearables and phone accessories; Battery sensors that report over a radio.
Wrong for: Heavy local computation; Wired-only designs, where the radio is wasted.

Example parts:

- Espressif ESP32-C6 (chip only): 1× RV32 high-performance core at 160 MHz + 1× RV32 low-power core at 20 MHz
- Espressif ESP32-S3 (chip only): 2× Xtensa LX7 at 240 MHz
- Nordic Semiconductor nRF54L15 (chip only): 1× Cortex-M33 at 128 MHz + 1× RISC-V coprocessor (VPR) at 128 MHz
- Silicon Labs EFR32MG24 (chip only): 1× Cortex-M33 at 78 MHz
- Texas Instruments CC2340R5 (chip only): 1× Cortex-M0+ at 48 MHz

### High-performance microcontroller

The simplicity of a microcontroller, with hundreds of MHz, megabytes of RAM and, increasingly, a small NPU or camera interface.

- CPU: Cortex-M7/M55/M85 or RISC-V, sometimes with a second core
- Clock: About 400 MHz to 1 GHz
- Memory: About 0.75 to 4 MB of SRAM; flash often external
- Software: Bare metal or RTOS, still no Linux
- Power: Tens to a few hundred milliwatts active, more with an NPU or GPU busy
- Acceleration: DSP or vector instructions; some parts add an NPU (hundreds of GOPS), a 2D GPU, a camera ISP or a video encoder

Good for: Touchscreen panels without Linux; Audio and vibration analysis; Small vision models such as person detection.
Wrong for: Coin-cell battery life; Software that expects Linux.

Example parts:

- Espressif ESP32-P4 (chip only): 2× RV32 high-performance core at 400 MHz + 1× RV32 low-power core at 40 MHz
- NXP i.MX RT1170 (chip only): 1× Cortex-M7 at 1 GHz + 1× Cortex-M4 at 400 MHz
- Renesas RA8M1 (chip only): 1× Cortex-M85 at 480 MHz
- STMicroelectronics STM32N657 (chip only): 1× Cortex-M55 at 800 MHz

### Entry application processor

The smallest chips that run Linux well: one or two efficient cores, often with a microcontroller core alongside.

- CPU: 1 or 2 cores (Cortex-A7/A35/A55, RISC-V), often plus a Cortex-M
- Clock: About 0.8 to 1.7 GHz
- Memory: External DRAM, 256 MB to 4 GB
- Software: Embedded Linux (Yocto, Buildroot); RTOS on the companion core
- Power: The lowest of the Linux-capable classes; usually fanless. Real figures depend on load, memory and peripherals, so measure your own board
- Acceleration: Some parts add a small NPU (around 0.5 to 1.5 TOPS)

Good for: Industrial HMIs and gateways; Linux devices on a power budget; Products that need Linux plus real-time control.
Wrong for: Years on a small battery; Heavy vision AI.

Example parts:

- Microchip SAMA7G54 (chip only): 1× Cortex-A7 at 1 GHz
- NXP i.MX 8ULP (chip only): 2× Cortex-A35 at 800 MHz + 1× Cortex-M33 at 216 MHz
- NXP i.MX 93 (chip only): 2× Cortex-A55 at 1.7 GHz + 1× Cortex-M33 at 250 MHz
- Renesas RZ/Five (chip only): 1× Andes AX45MP (RV64) at 1 GHz
- STMicroelectronics STM32MP157F (chip only): 2× Cortex-A7 at 800 MHz + 1× Cortex-M4 at 209 MHz
- STMicroelectronics STM32MP257F (chip only): 2× Cortex-A35 at 1.5 GHz + 1× Cortex-M33 at 400 MHz + 1× Cortex-M0+ at 200 MHz

### Mainstream application processor

Two- to four-core Linux processors that drive displays, run containers and act as gateways for many smaller devices.

- CPU: 2 to 4 cores (Cortex-A53/A55, RISC-V), often plus a Cortex-M
- Clock: About 1 to 2 GHz
- Memory: External DRAM, 512 MB to 8 GB
- Software: Linux (Yocto, Debian-based), Android
- Power: Higher than the entry class; usually still fanless, and normally mains-powered
- Acceleration: 3D GPU; some parts add a 1 to 2.3 TOPS NPU

Good for: IoT gateways and hubs; Touchscreen products; Learning Linux on real hardware.
Wrong for: Devices that must run for months on a battery; Hard real-time control without a companion core.

Example parts:

- Arduino UNO Q (board): 4× Cortex-A53 (Qualcomm Dragonwing QRB2210) at 2 GHz + 1× Cortex-M33 (separate STM32U585 chip) at 160 MHz
- NXP i.MX 8M Plus (chip only): 4× Cortex-A53 at 1.8 GHz + 1× Cortex-M7 at 800 MHz
- Raspberry Pi Zero 2 W (board): 4× Cortex-A53 at 1 GHz
- Renesas RZ/G2L (chip only): 2× Cortex-A55 at 1.2 GHz + 1× Cortex-M33 at 200 MHz
- Rockchip RK3568 (chip only): 4× Cortex-A55 at 2 GHz
- StarFive JH7110 (chip only): 4× SiFive U74 (RV64) at 1.5 GHz
- StarFive VisionFive 2 (board): 4× SiFive U74 (RV64) at 1.5 GHz
- Texas Instruments AM625 (chip only): 4× Cortex-A53 at 1.4 GHz + 1× Cortex-M4F at 400 MHz

### High-performance application processor

Fast cores and powerful accelerators for vision, multiple cameras and on-device AI.

- CPU: 4 to 8 cores: Cortex-A76/A78 class, usually paired with A55s; or many A55s; or x86-64
- Clock: About 1.7 to 3.4 GHz peak
- Memory: External DRAM, 1 to 16 GB; 4 GB or more for larger models
- Software: Linux, Ubuntu, Android, Windows IoT
- Power: Several watts to tens of watts under load; plan a heatsink or fan from the start
- Acceleration: NPU or GPU from about 2 to 67 TOPS. Vendors quote different precisions, and a sparse figure is about double the dense one

Good for: Multi-camera vision; Local inference on larger models; Robotics.
Wrong for: Devices on small batteries; Cost-sensitive products; Fanless enclosures without thermal planning.

Example parts:

- Broadcom BCM2712 (chip only): 4× Cortex-A76 at 2.4 GHz
- Intel Atom x7425E (chip only): 4× Efficient-core (Alder Lake-N) at 3.4 GHz
- MediaTek Genio 1200 (chip only): 4× Cortex-A78 at 2.2 GHz + 4× Cortex-A55 at 2 GHz
- NVIDIA Jetson Orin Nano 8GB (system-on-module): 6× Cortex-A78AE at 1.7 GHz
- NXP i.MX 95 (chip only): 6× Cortex-A55 at 2 GHz + 1× Cortex-M7 at 800 MHz + 1× Cortex-M33 at 333 MHz
- Qualcomm QCS6490 (chip only): 1× Kryo 670 Gold Prime at 2.7 GHz + 3× Kryo 670 Gold at 2.4 GHz + 4× Kryo 670 Silver at 1.9 GHz
- Raspberry Pi 5 (board): 4× Cortex-A76 at 2.4 GHz
- Rockchip RK3588 (chip only): 4× Cortex-A76 at 2.4 GHz + 4× Cortex-A55


## Sources

1. [The Linux Kernel Driver Interface (stable-api-nonsense)](https://docs.kernel.org/process/stable-api-nonsense.html), kernel.org
2. [NXP Product Longevity](https://www.nxp.com/products/product-information/product-longevity:PRDCT_LONGEVITY_HM), NXP
3. [Product Longevity Program (PLP)](https://www.renesas.com/en/support/product-longevity-program-plp), Renesas
4. [ISO 26262-1:2018 Road vehicles: Functional safety, Part 1: Vocabulary](https://www.iso.org/standard/68383.html), ISO
5. [IEC 61508: Functional safety of electrical/electronic/programmable electronic safety-related systems](https://webstore.iec.ch/en/publication/5515), IEC
6. [Functional Safety Support for Arm-based Microcontrollers and Processors (SPRADF6)](https://www.ti.com/lit/pdf/spradf6), Texas Instruments