computing, firmware is a computer program that is embeddedin a hardware device, for example a microcontroller. It can also be provided on flash memoryor as a binary image file that can be uploaded onto existing hardware by a user.
As its name suggests, firmware is somewhere between hardware and software. Like software, it is a computer program which is executed by a
microprocessoror a microcontroller. But it is also tightly linked to a piece of hardware, and has little meaning outside of it.
The term "firmware" was originally used for
micro-programs written for microsequencers such as AMD29xx.Later on, it was coined to indicate a functional replacement for hardware on low-cost microprocessors.
Evolved firmware uses
Firmware has evolved to mean the programmable content of a hardware device, which can consist of
machine languagefor a microprocessor, or configuration settings for a fixed-function device or programmable logic device. Many, though not all, devices have firmware that can be updated after manufacturing. This is usually done electronically in modern systems, however sometimes the storage medium containing the firmware, such as a socketed ROM, must be replaced.
Firmware may expose an externally accessible interface. For example, in some modem implementations the firmware is not directly accessible, but is part of a combination of hardware and firmware that responds to commands from the host system.
Firmware has traditionally been stored in ROM; however cost and performance requirements have driven component vendors to adopt various replacements, including non-volatile media such as
EEPROMand Flash, or SRAM solutions, such as the firmware loaded by an operating system device driver, as described below.
Firmware and device drivers
Most devices attached to modern systems are special-purpose computers in their own right, running their own software. Some of these devices store that software ("firmware") in a ROM within the device itself. Over the years, however, manufacturers have found that loading the firmware from the host system is both cheaper and more flexible. As a result, much current hardware is unable to function in any useful way until the host computer has fed it the requisite firmware. This firmware load is handled by the
Firmware in many devices can now be updated without the need for additional hardware, often through the use of vendor-provided software.
Firmware support challenges in PCs
In some respects firmware is as much a software component of a working system as the operating system. However, unlike most modern operating systems, firmware rarely has a well evolved mechanism for updating itself to fix bugs and addressing functionality issues that are detected after the unit is shipped.
The easiest firmware to update is typically the system boot-related firmware, such as the BIOS in PCs. Some devices, such as video adapters and modems, frequently rely on firmware that is loaded dynamically by the operating system device driver, and thus is updated through the operating system update mechanisms entirely transparent to the user.
In contrast, storage device firmware is rarely updated with the same consistency as other parts of the system. Further, the mechanisms for detecting firmware versions and updating them are not standardized. As a result, these devices tend to have a significantly higher percentage of firmware-driven functionality issues, as compared to other parts of a modern computer system.
Examples of firmware include:
BIOSfound in IBM-compatible Personal Computers;
platform codefound on Itaniumsystems, Intel-based Mac OS Xmachines, and many Intel desktop boards is EFI compliant firmware;
Open Firmware, used in computers from Sun Microsystemsand Apple Computer;
ARCS, used in computers from Silicon Graphics;
RTAS(Run-Time Abstraction Services), used in computers from IBM;
EPROMchips used in the Eventide H-3000 series of digital music processors.
iPod's control menus
Common Firmware Environment(CFE)
* Timing and control systems for
Sometimes an unofficial new or modified version of firmware is created by third parties to provide new features or unlock hidden functionality. Examples include
Rockboxfor digital audio players, CHDKfor Canon digital cameras, and OpenWRTfor wireless routers, as well as many homebrew projects for gaming consoles. These can often unlock general purpose computing functionality in previously limited devices (e.g., running Doom on iPods). Most firmware hacks are free and open sourcesoftware as well.
These hacks usually take advantage of the firmware update facility on many devices to install or run themselves. Some, however, must resort to exploits in order to run, because the manufacturer has attempted to lock the hardware to stop it from running unlicensed code.
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