Pi 5 vs Pi 4: What's Different and Migration Guide

What Actually Changed

• CPU: Broadcom BCM2712, quad-core Cortex-A76 @ 2.4GHz vs BCM2711 Cortex-A72 @ 1.5-1.8GHz — roughly 2-3x single-thread performance.
• PCIe: Pi 5 exposes a single-lane PCIe 2.0 connector (FPC, under the board) — this is huge for NVMe SSD boot and real M.2 hats.
• Power: Needs 5V/5A via USB-C PD, not the old 5V/3A. Old Pi 4 chargers will undervolt a Pi 5 under load.
• RTC: Onboard battery-backed real-time clock header (finally) — no more clock drift on headless boots without network.
• GPIO: Same 40-pin layout, but now routed through a separate RP1 southbridge chip instead of directly off the SoC — slightly higher GPIO latency for bit-banged timing-critical work (matters for some LED/servo libraries).
• Active cooling: Pi 5 needs a fan under sustained load — the official Active Cooler is basically mandatory for anything CPU-heavy.

Migration Checklist

1. Get a proper 27W USB-C PD supply — the official one, or anything that negotiates 5V/5A cleanly.
2. If you're booting from SD card today and want NVMe: you'll need a PCIe-to-M.2 hat (several vendors make these) plus a firmware/bootloader update via rpi-eeprom-update to enable PCIe boot.
3. Re-image with the latest Raspberry Pi OS (Bookworm) — older Bullseye images won't boot on Pi 5 hardware at all.
4. If you use GPIO libraries directly (RPi.GPIO, WiringPi), check compatibility — RP1 broke some low-level timing assumptions. lgpio or gpiozero with the rpi5 backend are the safer bets going forward.
5. Case fit: Pi 5's mounting holes and port layout shifted slightly — most Pi 4 cases won't fit.

When to Stick with Pi 4

If your project is I/O-bound (simple sensor logging, low-traffic web server, Pi-hole) rather than CPU-bound, the Pi 4 is still fine and often cheaper. Save the Pi 5 for camera/AI workloads, NVMe-backed NAS/server projects, or anything doing real compute (Frigate, local LLM inference, compiling).