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. 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 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. 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. 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. The following systems are known to work with &debian;/armhf using the multiplatform (armmp) kernel: Freescale MX53 Quick Start 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) and A20 (architecture codename sun7i) SoCs. Full installer support is currently available for the following sunXi-based systems: Cubietech Cubieboard 1 + 2 / Cubietruck LeMaker Banana Pi and Banana Pro LinkSprite pcDuino and pcDuino3 Mele A1000 Miniand Hackberry Olimex A10-Olinuxino-LIME / A10s-Olinuxino Micro / A13-Olinuxino / A13-Olinuxino Micro / A20-Olinuxino-LIME / A20-Olinuxino-LIME2 / A20-Olinuxino Micro PineRiver Mini X-Plus System support for Allwinner sunXi-based devices is limited to drivers and device-tree information available in the mainline Linux kernel. The android-derived linux-sunxi.org 3.4 kernel series is not supported by &debian;. The mainline Linux kernel generally supports serial console, ethernet, SATA, USB and MMC/SD-cards on Allwinner A10, A10s/A13 and A20 SoCs, but it does not have native drivers for the display (HDMI/VGA/LCD) and audio hardware in these SoCs. The NAND flash memory that is built into some sunXi-based systems is not supported. Using a local display is technically possible without native display drivers via the simplefb infrastructure in the mainline kernel, which relies on the U-Boot bootloader for initialising the display hardware, but this is not supported by the U-Boot version in &debian; 8. 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 Quad The Wandboard Quad is a development board based on the Freescale i.MX6 Quad SoC. System support for it 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 and SATA. Support for the onboard audio options (analog, S/PDIF, HDMI-Audio) and for the onboard WLAN/Bluetooth module is not available in &debian; 8. 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;. EfikaMX The EfikaMX platform (Genesi Efika Smartbook and Genesi EfikaMX nettop) was supported in &debian; 7 with a platform-specific kernel, but is no longer supported from &debian; 8 onwards. The code required to build the formerly used platform-specific kernel has been removed from the upstream Linux kernel source in 2012, so &debian; cannot provide newer builds. Using the armmp multiplatform kernel on the EfikaMX platform would require device-tree support for it, which is currently not available. The following platforms are supported by &debian;/armel; they require platform-specific kernels. IXP4xx The Intel IXP4xx processor series is used in commonly used network attached storage (NAS) devices like the Linksys NSLU2. While there is kernel support for this platform in &debian; 8, it is not supported by the &d-i;. It is possible to do a dist-upgrade from &debian; 7 to &debian; 8 for existing installations, though. Due to the small amount of RAM that systems based on the IXP4xx typically have, this requires that swap space is enabled prior to upgrading. Support for the IXP4xx platform will be dropped completely in &debian; 9. 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: OpenRD (OpenRD-Base, OpenRD-Client and OpenRD-Ultimate), plug computers (SheevaPlug, GuruPlug and DreamPlug), QNAP Turbo Station (all TS-11x, TS-21x and TS-41x models), and LaCie NASes (Network Space v2, Network Space Max v2, Internet Space v2, d2 Network v2, 2Big Network v2 and 5Big Network v2). 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 and HP mv2120. 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. MV78xx0 The MV78xx0 platform has been used on the Marvell DB-78xx0-BP development board. It was supported in &debian; 7 with a platform-specific kernel (based on the Linux kernel version 3.2), but is not supported any more from &debian; 8 onwards.