Firmware

From Wikipedia, the free encyclopedia

In computing, firmware is software that is embedded in a hardware device. It is often provided on flash ROMs or as a binary image file that can be uploaded onto existing hardware by a user.

1 Definitions
2 Origins
3 Evolved firmware uses
4 Firmware and device drivers
5 Firmware support challenges in PCs
6 Examples
7 See also
8 References
9 External links

[edit] Definitions

A typical vision of a computer architecture as a series of abstraction layers: hardware, firmware, assembler, kernel, operating system and applications (see also Tanenbaum 79).

Firmware is defined as:

the computer program in a read-only memory (ROM) integrated circuit (a hardware part number or other configuration identifier is usually used to represent the software);
the erasable programmable read-only memory (EPROM) chip, whose program may be modified by special external hardware, but not by [a general purpose] application program.^[1]

the electrically erasable programmable read-only memory (EEPROM) chip, whose program may be modified by special electrical external hardware (not the usual optical light), but not by [a general purpose] application program.

[edit] Origins

The term "firmware" was originally used for micro-programs written for micro sequencers such as AMD29xx. Later on, it was coined to indicate a functional replacement for hardware on low cost microprocessors.

Firmware in many devices can now be updated without the need for additional hardware, often through the use of vendor-provided software.

In practical terms, firmware updates can improve the performance and reliability, indeed even the basic available functionality of a device, and many devices benefit from regular firmware updates. One of the most common devices to have regular firmware updates are recording devices such as optical media writers (DVD, CD, HD DVD, Blu-ray), as media technologies extend, so firmware updates ensure hardware is kept up to date and compatible.

[edit] Evolved firmware uses

Firmware has evolved to mean the programmable content of a hardware device, which can consist of machine language instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device.

A typical common feature of firmware is that it can be updated post-manufacturing, either electronically, or by replacing a storage media such as a socketed memory chip.

Firmware can — but is not required to — 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 EEPROM and Flash, or SRAM solutions, such as the firmware loaded by an operating system device driver, as described below.

[edit] 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 device driver.

[edit] 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.

[edit] Examples

Examples of firmware include:

The BIOS found in IBM-compatible Personal Computers;
The EFI, found on Itanium systems, Intel-based Mac OS X machines, and as a secondary bootloader (which runs after the traditional BIOS) on x64 PCs;
The operating system on a router, such as the Linksys WRT54G
Open Firmware, used in computers from Sun Microsystems and Apple Computer;
ARCS, used in computers from Silicon Graphics;
RTAS (Run-Time Abstraction Services), used in computers from IBM;
EPROM chips used in the Eventide H-3000 series of digital music processors.
Adding features on the PSP
The iPod's control menus
The Common Firmware Environment (CFE)
Washing Machines (WM)
FPGA or CPLD programming files used to configure hardware for a variety of purposes.