# Three different ARM ports

The ARM architecture has evolved over time and modern ARM processors provide features which are not available in older models. &debian; therefore provides three ARM ports to give the best support for a very wide range of different machines:

- &debian;/armel targets older 32-bit ARM processors without support for a hardware floating point unit (FPU),

- &debian;/armhf works only on newer 32-bit ARM processors which implement at least the ARMv7 architecture with version 3 of the ARM vector floating point specification (VFPv3). It makes use of the extended features and performance enhancements available on these models.

- &debian;/arm64 works on 64-bit ARM processors which implement at least the ARMv8 architecture.

Technically, all currently available ARM CPUs can be run in either endian mode (big or little), but in practice the vast majority use little-endian mode. All of &debian;/arm64, &debian;/armhf and &debian;/armel support only little-endian systems.

## Variations in ARM CPU designs and support complexity

ARM systems are much more heterogeneous than those based on the i386/amd64-based PC architecture, so the support situation can be much more complicated.

The ARM architecture is used mainly in so-called system-on-chip (SoC) designs. These SoCs are designed by many different companies with vastly varying hardware components even for the very basic functionality required to bring the system up. System firmware interfaces have been increasingly standardised over time, but especially on older hardware firmware/boot interfaces vary a great deal, so on these systems the Linux kernel has to take care of many system-specific low-level issues which would be handled by the mainboard's BIOS/UEFI in the PC world.

At the beginning of the ARM support in the Linux kernel, the hardware variety resulted in the requirement of having a separate kernel for each ARM system in contrast to the one-fits-all kernel for PC systems. As this approach does not scale to a large number of different systems, work was done to allow booting with a single ARM kernel that can run on different ARM systems. Support for newer ARM systems is now implemented in a way that allows the use of such a multiplatform kernel, but for several older systems a separate specific kernel is still required. Because of this, the standard &debian; distribution only supports installation on a selected number of such older ARM systems, alongside the newer systems which are supported by the ARM multiplatform kernels (called armmp) in &debian;/armhf.

The ARM architecture is used mainly in so-called system-on-chip (SoC) designs. These SoCs are designed by many different companies, often with vastly varying hardware components even for the very basic functionality required to bring the system up. Older versions of the ARM architecture have seen massive differences from one SoC to the next, but ARMv8 (arm64) is much more standardised and so is easier for the Linux kernel and other software to support.

Server versions of ARMv8 hardware are typically configured using the Unified Extensible Firmware Interface (UEFI) and Advanced Configuration and Power Interface (ACPI) standards. These two provide common, device-independent ways to boot and configure computer hardware. They are also common in the x86 PC world.

## Platforms supported by Debian/arm64

Arm64/AArch64/ARMv8 hardware became available quite late in the &debian; &releasename-cap; release cycle so not many platforms had support merged in the mainline kernel version by the time of this release; this is the main requirement to have &d-i; working on them. The following platforms are known to be supported by &debian;/arm64 in this release. There is only one kernel image, which supports all the listed platforms.

Applied Micro (APM) Mustang/X-Gene

- The APM Mustang was the first Linux-capable ARMv8 system available. It uses the X-gene SoC, which has since also been used in other machines. It is an 8-core CPU, with ethernet, USB and serial. A common form-factor looks just like a desktop PC box, but many other versions are expected in the future. Most of the hardware is supported in the mainline kernel, but at this point USB support is lacking in the &releasename-cap; kernel.

ARM Juno Development Platform

- Juno is a capable development board with a 6-core (2xA57, 4xA53) ARMv8-A 800Mhz CPU, Mali (T624) graphics, 8GB DDR3 RAM, Ethernet, USB, Serial. It was designed for system bring-up and power testing so is neither small nor cheap, but was one of the first boards available. All the on-board hardware is supported in the mainline kernel and in &releasename-cap;.

When using &d-i; on non-UEFI systems, you may have to manually make the system bootable at the end of the installation, e.g. by running the required commands in a shell started from within &d-i;. flash-kernel knows how to set up an X-Gene system booting with U-Boot.

## Other platforms

The multiplatform support in the arm64 Linux kernel may also allow running &d-i; on arm64 systems not explicitly listed above. So long as the kernel used by &d-i; has support for the target system's components, and a device-tree file for that target is available, a new target system may work just fine. In these cases, the installer can usually provide a working installation, and so long as UEFI is in use, it should be able to make the system bootable as well. If UEFI is not used you may also need to perform some manual configuration steps to make the system bootable.

## Platforms supported by Debian/armhf

The following systems are known to work with &debian;/armhf using the multiplatform (armmp) kernel:

Freescale MX53 Quick Start Board (MX53 LOCO Board)

- The IMX53QSB is a development board based on the i.MX53 SoC.

Versatile Express

- The Versatile Express is a development board series from ARM consisting of a baseboard which can be equipped with various CPU daughter boards.

Certain Allwinner sunXi-based development boards and embedded systems

- The armmp kernel supports several development boards and embedded systems based on the Allwinner A10 (architecture codename sun4i), A10s/A13 (architecture codename sun5i), A20 (architecture codename sun7i), A31/A31s (architecture codename sun6i) and A23/A33 (part of the sun8i family) SoCs. Full installer support (including provision of ready-made SD card images with the installer) is currently available for the following sunXi-based systems:

  - Cubietech Cubieboard 1 + 2 / Cubietruck

  - LeMaker Banana Pi and Banana Pro

  - LinkSprite pcDuino and pcDuino3

  - Olimex A10-Olinuxino-LIME / A20-Olinuxino-LIME / A20-Olinuxino-LIME2 / A20-Olinuxino Micro / A20-SOM-EVB

  - Xunlong OrangePi Plus

  System support for Allwinner sunXi-based devices is limited to drivers and device-tree information available in the mainline Linux kernel. Vendor-specific kernel trees (such as the Allwinner SDK kernels) and the android-derived linux-sunxi.org kernel 3.4 series are not supported by &debian;.

  The mainline Linux kernel generally supports serial console, ethernet, SATA, USB and MMC/SD-cards on Allwinner A10, A10s/A13, A20, A23/A33 and A31/A31s SoCs. The level of support for local display (HDMI/VGA/LCD) and audio hardware varies between individual systems. For most systems, the kernel doesn't have native graphics drivers but instead uses the simplefb infrastructure in which the bootloader initializes the display and the kernel just re-uses the pre-initialized framebuffer. This generally works reasonably well, although it results in certain limitations (the display resolution cannot be changed on the fly and display powermanagement is not possible).

  Onboard flash memory intended to be used as a mass storage device generally exists in two basic variants on sunXi-based systems: raw NAND flash and eMMC flash. Most older sunXi-based boards with onboard flash storage use raw NAND flash for which support is not generally available in the mainline kernel and therefore also not in Debian. A number of newer systems use eMMC flash instead of raw NAND flash. An eMMC flash chip basically appears as a fast, non-removable SD card and is supported in the same way as a regular SD card.

  The installer includes basic support for a number of sunXi-based systems not listed above, but it is largely untested on those systems as the &debian; project doesn't have access to the corresponding hardware. No pre-built SD card images with the installer are provided for those systems. Development boards with such limited support include:

  - Olimex A10s-Olinuxino Micro / A13-Olinuxino / A13-Olinuxino Micro

  - Sinovoip BPI-M2 (A31s-based)

  - Xunlong Orange Pi (A20-based) / Orange Pi Mini (A20-based)

  In addition to the SoCs and systems listed above, the installer has very limited support for the Allwinner H3 SoC and a number of boards based on it. Mainline kernel support for the H3 is still largely work in progress at the time of the Debian 9 release freeze, so the installer only supports serial console, MMC/SD and the USB host controller on H3-based systems. There is no driver for the on-board ethernet port of the H3 yet, so networking is only possible with a USB ethernet adaptor or a USB wifi dongle. Systems based on the H3 for which such very basic installer support is available include:

  - FriendlyARM NanoPi NEO

  - Xunlong Orange Pi Lite / Orange Pi One / Orange Pi PC / Orange Pi PC Plus / Orange Pi Plus / Orange Pi Plus 2E / Orange Pi 2

NVIDIA Jetson TK1

- The NVIDIA Jetson TK1 is a developer board based on the Tegra K1 chip (also known as Tegra 124). The Tegra K1 features a quad-core 32-bit ARM Cortex-A15 CPU and Kepler GPU (GK20A) with 192 CUDA cores. Other systems based on the Tegra 124 may work, too.

Seagate Personal Cloud and Seagate NAS

- The Seagate Personal Cloud and Seagate NAS are NAS devices based on Marvell's Armada 370 platform. Debian supports the Personal Cloud (SRN21C), Personal Cloud 2-Bay (SRN22C), Seagate NAS 2-Bay (SRPD20) and Seagate NAS 4-Bay (SRPD40).

SolidRun Cubox-i2eX / Cubox-i4Pro

- The Cubox-i series is a set of small, cubical-shaped systems based on the Freescale i.MX6 SoC family. System support for the Cubox-i series is limited to drivers and device-tree information available in the mainline Linux kernel; the Freescale 3.0 kernel series for the Cubox-i is not supported by &debian;. Available drivers in the mainline kernel include serial console, ethernet, USB, MMC/SD-card and display support over HDMI (console and X11). In addition to that, the eSATA port on the Cubox-i4Pro is supported.

Wandboard

- The Wandboard Quad, Dual and Solo are development boards based on the Freescale i.MX6 Quad SoC. System support is limited to drivers and device-tree information available in the mainline Linux kernel; the wandboard-specific 3.0 and 3.10 kernel series from wandboard.org are not supported by &debian;. The mainline kernel includes driver support for serial console, display via HDMI (console and X11), ethernet, USB, MMC/SD, SATA (Quad only) and analog audio. Support for the other audio options (S/PDIF, HDMI-Audio) and for the onboard WLAN/Bluetooth module is untested or not available in &debian; 9.

Generally, the ARM multiplatform support in the Linux kernel allows running &d-i; on armhf systems not explicitly listed above, as long as the kernel used by &d-i; has support for the target system's components and a device-tree file for the target is available. In these cases, the installer can usually provide a working installation, but it may not be able to automatically make the system bootable. Doing that in many cases requires device-specific information.

When using &d-i; on such systems, you may have to manually make the system bootable at the end of the installation, e.g. by running the required commands in a shell started from within &d-i;.

## Platforms supported by Debian/armel

The following platforms are supported by &debian;/armel; they require platform-specific kernels.

Kirkwood

- Kirkwood is a system-on-chip (SoC) from Marvell that integrates an ARM CPU, Ethernet, SATA, USB, and other functionality in one chip. &debian; currently supports the following Kirkwood based devices:

  - Plug computers (SheevaPlug, GuruPlug, DreamPlug and Seagate FreeAgent DockStar)

  - LaCie NASes (Network Space v2, Network Space Max v2, Internet Space v2, d2 Network v2, 2Big Network v2 and 5Big Network v2)

  - OpenRD (OpenRD-Base, OpenRD-Client and OpenRD-Ultimate)

Orion5x

- Orion is a system-on-chip (SoC) from Marvell that integrates an ARM CPU, Ethernet, SATA, USB, and other functionality in one chip. There are many Network Attached Storage (NAS) devices on the market that are based on an Orion chip. &debian; currently supports the following Orion based devices: Buffalo Kurobox.

Versatile

- The Versatile platform is emulated by QEMU and is therefore a nice way to test and run &debian; on ARM if you don't have real hardware.

## Devices no longer supported by Debian/armel

Kirkwood

- Support for all QNAP Turbo Station models (TS-xxx) has been dropped for &debian; 11, since the Linux kernel for them can no longer being built, due to hardware limitations.

Orion5x

- Support for HP Media Vault mv2120 has been dropped for &debian; 11, since the Linux kernel for it can no longer being built, due to hardware limitations.

You may be able to keep above listed devices running for some time, see the Release Notes for &debian; 11.