Editing BIOS (section)

== {{Anchor|COMPARISON}}Vendors and products ==
{| class="wikitable floatright" style="margin-left: 2em;"
|+ Comparison of different BIOS implementations
|-
! Company
| [[Award Software|AwardBIOS]]
| [[American Megatrends|AMIBIOS]] <!--latest version is 8 -->
| [[Insyde Software|Insyde]]
| [[SeaBIOS]]
|-
! License
| {{Proprietary}}
| {{Proprietary}}
| {{Proprietary}}
| {{open source|[[GNU Lesser General Public License|LGPL]] v3}}
|-
! Maintained / developed
| {{Terminated}}
| {{Terminated}}
| {{Terminated}}
| {{Yes}}
|-
! [[32-bit computing|32-bit]] PCI BIOS calls
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! {{Abbr|AHCI|Advanced Host Controller Interface}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! {{Abbr|APM|Advanced Power Management}}
| {{Yes}}
| {{Yes}}
| {{Yes}} <small>(1.2)</small>
| {{Yes}} <small>(1.2)</small>
|-
! {{Abbr|BBS|BIOS Boot Specification}}
| {{Yes}}
| {{Yes}} <!-- SATA, IDE, USB, LAN, Floppy -->
| {{Yes}}
| {{Yes}}
|-
! Boot menu
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! Compression
| {{Yes}} <small>([[LHA (file format)|LHA]]<ref name="prozessor-patches" />)</small>
| {{Yes}} <small>(LHA)</small>
| {{Yes}} <small>(RLE)</small>
| {{Yes}} <small>(LZMA)</small>
|-
! CMOS
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! {{Abbr|EDD|Enhanced Disk Drive}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! {{Abbr|ESCD|Extended System Configuration Data}}
| {{Yes}}
| {{Yes}}
| {{Dunno}}
| {{No}}
|-
! Flash from ROM
| {{Dunno}}
| {{Yes}} <!-- Qflash, Del-key -->
| {{Dunno}}
| {{No}}
|-
! Language
| Assembly
| Assembly
| Assembly
| [[C (programming language)|C]]
|-
! {{Abbr|LBA|Logical Block Addressing}}
| {{Yes}} <small>(48)</small>
| {{Yes}} <small>(48)</small>
| {{Yes}}
| {{Yes}} <small>(48)</small>
|-
! MultiProcessor Specification
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! Option ROM
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! Password
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{No}}
|-
! {{Abbr|PMM|Post Memory Manager}}
| {{Dunno}}
| {{Yes}}
| {{Dunno}}
| {{Yes}}
|-
! Setup screen
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{No}}
|-
! {{Abbr|SMBIOS|System Management BIOS}}
| {{Yes}} <!-- 2.4 or newer -->
| {{Yes}} <!-- 2.5 or newer -->
| {{Yes}} <!-- 2.6 or newer -->
| {{Yes}}
|-
! Splash screen
| {{Yes}} <small>(EPA)<ref>{{cite web |url=http://fileformats.archiveteam.org/wiki/Award_BIOS_logo |title=Award BIOS logo |date=2015-06-15 |access-date=2015-12-06 |url-status = live|archive-url=https://web.archive.org/web/20151221152258/http://fileformats.archiveteam.org/wiki/Award_BIOS_logo |archive-date=2015-12-21 }}</ref></small>
| {{Yes}} <small>([[PCX]])</small> <!-- 640x480x256 pcx -->
| {{Yes}}
| {{Yes}} <small>(BMP, JPG)</small> <!-- JPEG would use 16 or 24 bpp video mode, BMP use 24bpp mode only -->
|-
! {{Abbr|TPM|Trusted Platform Module}}
| {{Unknown}}
| {{Yes}}
| {{Unknown}}
| {{Yes|Some}}
|-
! [[USB]] booting
| {{Yes}}
| {{Yes}}
| {{Yes}} <!-- at least USB floppy -->
| {{Yes}}
|-
! USB hub
| {{Dunno}}
| {{Dunno}}
| {{Dunno}}
| {{Yes}}
|-
! USB keyboard
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|-
! USB mouse
| {{Yes}}
| {{Yes}}
| {{Yes}}
| {{Yes}}
|}

IBM published the entire listings of the BIOS for its original PC, PC XT, PC AT, and other contemporary PC models, in an appendix of the ''IBM PC Technical Reference Manual'' for each machine type. The effect of the publication of the BIOS listings is that anyone can see exactly what a definitive BIOS does and how it does it.

[[File:Compaq Portable 386 BIOS.jpg|thumb|[[Compaq Portable]] 386 BIOS]]
In May 1984, [[Phoenix Technologies|Phoenix Software Associates]] released its first ROM-BIOS. This BIOS enabled OEMs to build essentially fully compatible clones without having to reverse-engineer the IBM PC BIOS themselves, as Compaq had done for the [[Compaq Portable|Portable]]; it also helped fuel the growth in the PC-compatibles industry and sales of non-IBM versions of DOS.<ref>[https://books.google.com/books?id=zzAEAAAAMBAJ&pg=PA8 Phoenix Eagerly Waiting to Clone Next-Generation IBM BIOS]. {{webarchive|url=https://web.archive.org/web/20140122080016/http://books.google.com/books?id=zzAEAAAAMBAJ&pg=PA8 |date=2014-01-22 }}, ''InfoWorld'', 9 March 1987.</ref> The first [[American Megatrends]] (AMI) BIOS was released in 1986.

New standards grafted onto the BIOS are usually without complete public documentation or any BIOS listings. As a result, it is not as easy to learn the intimate details about the many non-IBM additions to BIOS as about the core BIOS services.

Many PC motherboard suppliers licensed the BIOS "core" and toolkit from a commercial third party, known as an "independent BIOS vendor" or IBV. The motherboard manufacturer then customized this BIOS to suit its own hardware. For this reason, updated BIOSes are normally obtained directly from the motherboard manufacturer. Major IBVs included [[American Megatrends]] (AMI), [[Insyde Software]], [[Phoenix Technologies]], and Byosoft. Microid Research and [[Award Software]] were acquired by [[Phoenix Technologies]] in 1998; Phoenix later phased out the Award brand name (although Award Software is still credited in newer AwardBIOS versions and in UEFI firmwares).{{when|date=June 2024}} [[General Software]], which was also acquired by Phoenix in 2007, sold BIOS for embedded systems based on Intel processors.

[[SeaBIOS]] is an open-source BIOS implementation.