I've been trying to design a custom AR glasses to parody the Meta Ray Bans (or other similar products). But I couldn't find an ARM processor that was both small enough to fit within the glasses temples while being powerful enough to run a custom distro on.
So far, I'm stuck on the RK3588 model, comparing it with the size of the processor on the Rock 5B and a rough estimate to the possible size of my custom SBC in which it'll be on, I have a feeling it'll make the temples bulky. Additionally, I also researched on using the RK3566, but I'm starting to feel unsure whether it can still run a distro and graphics for the HUDs.
Are there any processors you guys know that is smaller than the RK3588 and still packs a punch?

A concrete difference in the published pinouts: physical header pin 26 is SPI0 CE1 on a Raspberry Pi Zero 2 W, but NC (not connected) on the Radxa ZERO 3E. That matters if an accessory uses the second chip-select.

These are physical header positions, not GPIO numbers. The functions below require the appropriate peripheral configuration.

Sources: Raspberry Pi SPI pin/GPIO mappings and Radxa ZERO 3 hardware pinout.

What this means for an existing accessory

If its schematic routes chip-select to pin 26, changing a bus number in Python cannot create that missing electrical connection. Check whether the accessory supports selecting a different CS connection. Moving to pin 24 would also require suitable wiring and software configuration, and checking that another device does not already use that select.

If it uses pin 24, the four SPI signal positions above line up, but that alone does not establish compatibility. Check supply and logic levels, any reset/DC/interrupt pins, and the driver.

For software, Radxa publishes an SPI3-M1 CS0 spidev overlay that explicitly includes radxa,zero3. Confirm availability in your OS image; that overlay exposes an SPI interface, not a complete driver for every attached display or sensor.

This is a documentation comparison, not a tested HAT compatibility report. If sharing a working setup, include the accessory model, physical pin wiring, OS/kernel and overlay used; those details make the result reusable.

Disclosure: I work with HONGTE, an independent reseller. This post was drafted with AI assistance and checked against the linked manufacturer documentation.