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eine deutsche Übersetzung gibt es hier: FAQDe

Fundamental questions

What is this site about?

Welcome to the XDA-Developers wiki!

For information on XDA-Developers itself, see the About page

This wiki covers a wide range of devices, platforms, guides and topics for both end users and technical developers.

Can't find your device?

A wide range of legacy PDA-phones manufactured by the Taiwanese company HTC are rebranded. These phones are sold under a variety of different brand names by different providers, even though the actual device is the same. If your device matches the device here, it most likely is the same device. Most aliases are listed alongside the HTC name.

Technical Terms and Jargon

It has been suggested that this article or section be merged with acronyms. (Discuss)
It has been suggested that this article or section be merged with glossary. (Discuss)
It has been suggested that this article or section be merged with jargon list. (Discuss)

Telephony Networks

  • GSM/UTMS: A system of mobile radio communications. Most commonly seen as 1X, 3G, or 4G. In some languages, GSM also refers to the mobile phone itself.
  • CDMA: Similar to GSM, but a different standard. Most commonly seen as 1X (analog), 3G, or 4G LTE.


  • IPL: Initial Program Loader - usually paired with Secondary Program Loader (SPL), is the boot loader of your phone, much like the BIOS is the boot loader for your PC. Note: IPL/SPL are highly hardware dependent, flashing the wrong IPL/SPL is much more serious than a flashing the wrong ROM. It may be noted that, sometimes a ROM package also contains the IPL/SPL which will be flashed into your phone. Hence be extra careful what you are flashing. Note: although a ROM may also contains the IPL/SPL, `ROM` usually refers just to the OS (eg. the Windows Phone 7, not the IPL/SPL) and the ExtRom.
  • SPL: Refer to "IPL"; see also SPL
  • ROM: Read Only Memory - commonly used in the form of `ROM upgrade`. The ROM is the firmware/software, which controls everything on your phone. ROM itself usually comes in a package, with IPL/SPL, OS, Radio, and ExtRom. However, in most cases, `upgrading a ROM` usually means just the OS and the ExtRom, as these are the obvious/visible part of a ROM upgrade.
  • OS: Operating System - the platform software for your phone, much like Windows 7 for your PC. Upgrading the OS is like, in PC terms, upgrading from Windows XP to Windows 7.
  • ExtROM: Extended ROM - is the section of the ROM which the distributor of the phone (eg O2, T-Mobile, iMate, etc) store their customization (eg Today theme, ring tones, extra software) data. In WM5, the customization data will be automatically installed after the initial configuration (after every hardreset), just after the security section. In most cases, ExtROM can be unlocked to allow users to store/build their own customizations that will be automatically installed upon every hardreset.
  • CID: Carrier Id - commonly used in the form `CID-Unlocking`. If you purchase your phone (example) from Qtek (Qtek is the 'carrier'), your phone will only accept Qtek ROMs (the carrier's ROMs). If you want to flash ROMs from other carrier, you'll need to CID-unlock your phone, so that your phone will accept other ROMs. Note: In general, the phrase 'unlock your phone' usually refers to SIM-unlock, not CID unlock.
  • Radio: Also referred as GSM (see below) - commonly used in the form `upgrading the Radio/GSM` - in the field of ROM upgrading. The `Radio` is essentially a ROM that controls the phone function part (as oppose to PDA function part) of your phone. Upgrading this `Radio` software may have effect on your phone reception quality, battery life (optimized phone function), signal strength, etc.
  • GSM: A system of mobile radio communications. Most common 2G standard. Often used on xda-developers somewhat confusingly to refer to the radio protocol stack or `Radio` in XDA devices. This is slightly misleading as 3G HTC phones use a W-CDMA stack for the 3G communications, and GSM for 2G. In some languages, GSM also refers to the mobile phone itself.
  • Protocol: Similar to `Radio`. Both terms refer to the radio protocol stack, which is the software which handles communications with the mobile network.
  • SIM: Subscriber Identity Module - commonly used in the form `SIM unlock`. Some phones are locked to the specific telco from which you purchase your phone, eg you can't use a locked O2 phone using a Vodaphone SIM/smart card. To use SIM card from other telco, you need to SIM unlock your phone. Note: In general, the phrase 'unlock your phone' usually refers to SIM-unlock, not CID unlock.
  • AKU: Adaptation Kit Update - Starting with Windows Mobile 5 Microsoft began a policy of updates similar to that of the desktop windows. Rather the replacing the whole OS some functionality may be added. For example AKU 2.0 introduced push mail. These updates are distributed through the OEMs and are given to the consumer in form of ROM updates. Note that OEM may choose not to create an update with the latest AKU for their devices. Getting an AKU for your phone is like getting the SP1 (Service Pack 1) for your Windows 7.

Windows Mobile 5 (WM5) and later (WM6, WM6.x)

  • Storage memory: The persistent memory part of WM5, where all the files and documents are kept, much like the hard disk of your PC. Data in the storage memory is unaffected by soft-reset or a flat battery. You can't adjust the ratio of Storage memory and Program memory in WM5 like WinCE2003.
  • Program memory: The non-persistent memory part of WM5, which is used for all the temporary memory requirements, much like the RAM of your PC. A soft-reset or flat battery will erase everything from the program memory. You can't adjust the ratio of Storage memory and Program memory in WM5 like WinCE2003.


  • SIM Unlock: Use any carrier's SIM in the device.
  • CID Unlock: Load any carrier ROM (in any language) on the device.
  • Application Unlock: Most WM5 phones only allow you to load applications that have an acceptable digital signature. If you try to edit the registry or load an application it will give you an error. Application Unlocking removes this barrier and allows you to install any application or edit the registry to your liking.


  • CFS: Completely Fair Scheduler - The original process scheduler. CFS is better for multitasking, BFS is better for user interactions
  • BFS: Brain F**k Scheduler - The updated and improved process scheduler. CFS is better for multitasking, BFS is better for user interactions
  • SVS: Static Voltage Scaling will change the voltage based on a set table created by the kernel maker. Example: At a certain speed, say 245MHz, 925mV is feed into the CPU. At 998MHz, 1225mV is used.
  • AVS: Adaptive Voltage Scaling will change the voltage depending on temperature and CPU needs.
  • HAVS: Under volts and under clocks the processor when it's not being used.
  • BFQ: I/O scheduler - Schedules read and write operations to the SD? or Processor?
  • AXI: AXI (internal bus). Reduces speed when the apps CPU is running at lower clock speeds and increases it when at higher clock speeds.
  • UVOC: Undervolted Overclocked. Reduce the voltage supply to the processor for power saving at lower speeds, along with overclocking the processor at the save voltage as the previous max value. 1250mV @ 998MHz - 1250mV at 1190MHz, -or- 245MHz @ 1000mV - 245MHz @ 900mV.
  • SLAB: Slab allocation is a memory management mechanism intended for more efficient memory allocation and to eliminate memory fragmentation
  • SLUB: SLUB allocator, a drop-in replacement for the slab code. SLUB promises better performance and scalability by dropping most of the queues and related overhead and simplifying the slab structure in general.
  • SLQB: A slab allocator that focuses on per-CPU scaling, and good performance with order-0 allocations.
  • EXT2: The ext2 or second extended filesystem is a file system for the Linux kernel.
  • EXT3: The ext3 or third extended filesystem is a journaled file system that is commonly used by the Linux kernel.
  • EXT4: The ext4 or fourth extended filesystem is a journaling file system for Linux. Should offer improved performance over ext2/3.
  • CIFS: Common Internet File System (CIFS) operates as an application-layer network protocol, mainly used to provide shared access to files across a network.
  • TUN:
  • AUFS: AUFS is a complete rewriting of the earlier UnionFS file system. It aimed to improve reliability and performance.
  • ReiserFS: ReiserFS is a general-purpose, journaled computer file system. Performance is good, but performance can degrade with constant use.

FAQ on your OS and phones

For further Frequently Asked Questions, please select the FAQ on your OS and phones: