Native Linux on Apple A5 — the first step of the Cascadia project (A5 → A6 → A12/A13)
Status: Phase 1 Complete — Linux boots to shell
Cascadia is an attempt to run native, mainline Linux on Apple A5-based devices — starting with the iPad mini 1 (iPad2,5).
As of writing, no prior Linux port exists for the A5 (S5L8942X). PostmarketOS covers A8+, Project Sandcastle targeted A10, but A5 has been a complete blind spot. Cascadia aims to change that.
The goal is not just to boot Linux — it's to build a foundation for future ports to A6, A10, and eventually A12/A13 (via usbliter8), documenting everything along the way so others can build on it.
- checkm8 BootROM exploit covers A5 (permanent, hardware-level)
- No prior Linux work — genuinely uncharted territory
- A5 uses Samsung-derived IP blocks (UART, cache) with partial open documentation — more approachable than newer Apple-custom silicon
- PowerVR SGX543 GPU has some open documentation (future goal)
| Device | Model | Chip | Board ID |
|---|---|---|---|
| iPad mini 1 (Wi-Fi) | iPad2,5 / A1432 | Apple A5 (S5L8942X) | p105ap |
More devices planned as the project matures.
- checkm8 via Raspberry Pi Pico (checkm8-a5)
- Full boot chain: primepwn → autogo iBEC → staging-bundle → Linux
- Linux 6.12 kernel boots on hardware
- Apple DeviceTree fully parsed, all hardware addresses extracted
- Custom Linux DTS (memory, UART0, AIC1, simplefb, PL310 L2)
- Custom AIC1 interrupt controller driver
- PMCCNTR clocksource (Cortex-A9 cycle counter)
- Serial output via DCSD cable — kernel logs confirmed
- simplefb framebuffer — /dev/fb0 registered, Tux on screen
- Alpine Linux 3.24 embedded initramfs
- Interactive shell on tty0 (framebuffer console)
- USB networking (OTG PHY needs driver)
- CPU1 / SMP bringup (entry point research in progress)
- WiFi (BCM4334 via SDIO)
- Touch input
Phase 1 ✓: Linux boots to interactive shell. Serial logs. Framebuffer console. Phase 2 (current): USB gadget ethernet → SSH → package manager → fastfetch. Phase 3: CPU1 SMP bringup. WiFi via brcmfmac. Phase 4: A6 port (iPhone 5 / iPad mini 2). Build on Phase 1 foundation. Phase 5: A12/A13 via usbliter8 (longer term).
Hardware addresses extracted directly from Apple's DeviceTree:
| Peripheral | Physical Address | Notes |
|---|---|---|
| UART0 | 0x32500000 | boot-console, earlycon=s3c6400 |
| AIC | 0x3F200000 | Custom aic,1 driver (not mainline) |
| PL310 L2 | 0x3E000000 | Disabled — hangs with L1 D-cache off |
| Framebuffer | 0x9F6FC000 | 768×1024, stride 3072, BGRA8888 |
| RAM base | 0x80000000 | 512MB |
Boot chain uses autogo-patched iBEC (teutekeune/iBSSloader) + staging-bundle (linux-boot loader + zImage-dtb at 0x80008000).
In May 2026, while looking for existing Linux ports for the iPad mini 1, I found nothing. PostmarketOS stops at A8, Project Sandcastle targeted A10, and the A5 had been completely ignored — likely because it's 32-bit, old, and "not worth it".
That's exactly why it's interesting.
The A5 (S5L8942X) is covered by checkm8, uses Samsung-derived IP blocks with partial open documentation, and has PowerVR SGX543 GPU which has more public info than Apple's custom silicon. It's arguably one of the more approachable chips for a from-scratch Linux port.
This project started as an experiment to see how far you can get. Turns out — pretty far.
- teutekeune — iBSSloader: useful info - kernel patches, boot chain, AIC1 driver
- axi0mX — checkm8 BootROM exploit
- LukeZGD — Legacy iOS Kit, EverPwnage, checkm8-a5 Pico firmware
- NyanSatan — checkm8_bootkit, iBoot research
- iH8sn0w — iBoot32Patcher
GPL-2.0