AMIBIOS

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AMIBIOS, commonly stylized as AMI BIOS, is an IBM PC-compatible BIOS. It was first released by Access Methods Inc. in 1985 and later developed by American Megatrends (now AMI Inc.). It is also one of the first IBM PC-compatible BIOS firmware that were mass licensed for clone systems, released shortly after the competing PhoenixBIOS by Phoenix Technologies. Similar to that, it was also reverse engineered under a clean room solution to avoid infringement of IBM BIOS' copyright.

Its latest mainstream version, AMIBIOS 8, was phased out on most platforms released after 2010, in favor of modern UEFI-based firmware solutions (such as AMI Aptio or InsydeH2O, former of which developed by the same company). Despite this, it is still used on some industrial systems (such as the ones with the Vortex86 SoC) that are based on legacy platforms. It is also commonly used on newer motherboards for legacy platforms, especially LGA 775 and 1156. Aside from this, earlier instances of AMI Aptio contained an embedded version of AMIBIOS 8 as a component module for legacy boot (CSM) only mode. However, since CSM was discontinued by Intel in 2020[1], this mode was removed along with its module. It should also be noted that this module was not used for UEFI boot mode with CSM support.

Acquisition from Access Methods Inc.

Main page: American Megatrends

Access Methods Inc., a joint venture by Subromanian Shankar and Pat Sarma, released the first version of AMIBIOS in 1985.[2] Shortly after and due to legal issues, the owners found a new company with the funds raised by this joint venture. This venture was founded as Quintessential Consultants Inc. (QCI) and later renamed to American Megatrends Inc. (AMI) to keep the "AMIBIOS" acronym. The venture then acquired AMIBIOS from Access Methods next year.[3]

List of known versions

All versions predating AMI Plus BIOS were initially released by Access Methods. Therefore, in most instances (ROMs), these versions' copyright string mentions "Access Methods Inc.". However, some of these versions were later updated by American Megatrends. Therefore, the copyright string of ROMs based on these updated cores may mention "American Megatrends Inc." instead.

In most cases, ROMs of all versions from AMIBIOS 2.x to AMIBIOS 6 and AMIBIOS 7 can be identified by the date shown in the identification string (which is almost always shown at the bottom left of the POST screen). Because these dates are fixed to the initial release date of the AMIBIOS core version. However, occasionally, some OEMs modified these dates to reflect the ROM compile/release date instead of the core release date, especially on earlier versions released before AMI WinBIOS (AMIBIOS 4). On AMIBIOS 07.00.xx and AMIBIOS 8, the identification string date was changed to reflect the ROM compile date instead of the core release date. Therefore, these versions do not have fixed core dates and therefore cannot be identified

Notice: Due to lack of information and references, the names for all versions released before the AMI Hi-Flex BIOS are assumed based on little and unofficial information available. When more information is available, these will be corrected.

Version name First release date POST screen (if available) Known core dates Notes
AMIBIOS 1.x 1985 Not available The first version of AMIBIOS, currently no ROMs or pictures are available.
AMIBIOS 2.x 1986 The name is assumed based on information from the unofficial MR BIOS website[4] and therefore may not be correct.
AMI Plus BIOS(?) 1987 The name is assumed based on information from the unofficial MR BIOS website[5] and may not be correct. Unofficially also called the AMI Pre-Color BIOS due to its monochrome setup utility, which came out before the AMI Hi-Flex BIOS with its colorful utility.
AMI Hi-Flex BIOS November 1990 Not to be confused with the Hi-Flex Setup Utility on AMIBIOS 6 and 07.00.10, which was named after it. Unofficially also called AMI Color BIOS due to its colorful setup utility. Likely and internally also called AMIBIOS 3, although unconfirmed.
AMI WinBIOS (AMIBIOS 4) December 1993 Often referred to as the AMI WinBIOS, not to be confused with the WinBIOS Setup Utility on AMIBIOS 6 (which was named after it).
AMIBIOS 5 October 1994 10/10/94 Visually almost identical to the AMIBIOS 4, although contains new features and likely also initial bug fixes.
AMIBIOS 6 July 1995 07/15/95

07/15/97 07/15/99

Also known as AMIBIOS 97 (1997), AMIBIOS 98 (1998) and AMIBIOS 99 (1999)[6][7]
AMIBIOS 07.00.xx 1999-2000 Not used Commonly known as both AMIBIOS 07.00.xx and 07.00.00, officially called AMIBIOS V7.0[8]. Not to be confused with AMIBIOS 07.00.10.
AMIBIOS 7 April 2001 04/02/01 It is assumed to be an update to the AMIBIOS 6 codebase (possibly for meeting the PC 2001 requirements) that was named 07.00.10 likely for marketing reasons only.
AMIBIOS 8 October 2001 Not used Last commercial version of AMIBIOS. May possibly be an update to AMIBIOS 07.00.xx for meeting the PC 2001 requirements, although this is only a theory.
AMIBIOS 9 Unknown Not available. Not used Used in Microsoft Hyper-V. Assumed to be the name given to the BIOS emulation component for CSM/legacy mode in AMI Aptio.

ROM identification string

The ROM identification string was first introduced with AMIBIOS 2.x and is often located at the bottom left of the POST screen. With this string, many useful details regarding the BIOS ROM can usually be gathered, such as the ROM size, chipset, motherboard manufacturer and sometimes even the AMIBIOS version. The string is formatted into sections with each containing different information regarding the ROM. The known codes for these sections are listed in the list of codes for BIOS strings (also available at the bottom of this page). The string format has been changed various times with some new releases of AMIBIOS.

AMIBIOS 2.x

MMMM-SSSSSS

  • MMMM: Manufacturer/OEM identification code
  • SSSSSS: AMIBIOS version release date

Example string: 1406-061286

This string is for an AMIBIOS 2.x version released on June 12, 1986 ("061286") for Flying Triumph Co. Ltd. ("1406").

AMI Plus BIOS

DCCC-MMMM-SSSSSS-KK

  • D: CMOS setup type
    • Note: This section can also be two characters long for "DE" if the ROM contains both built-in diagnostics and an extended setup.
  • CCC: Chipset type
  • MMMM: Manufacturer/OEM identification code
  • SSSSSS: BIOS version release date
  • KK: Keyboard controller ID (with second character indicating the model).

Example string: D286-1277-043089-K0

This string is for an AMI Plus BIOS version released on April 30, 1986 ("043089") with built-in diagnostics ("D") for a machine with a discrete logic chipset for 80286 ("286") and a default/unknown keyboard controller (K"0") for Trangg Bow Co. ("1277").

AMI Hi-Flex BIOS and later versions

CR-VVVV-00MMMM-FFFFFFFF-SSSSSS-DDDDDDDD-Project-Y2KC-K

  • C: Processor architecture
  • R: ROM size
  • MMMM: Manufacturer/OEM identification code
  • FFFFFFFF: BIOS feature identification
    • Usually "00101111" which is the default.
  • SSSSSS: BIOS compile date (AMIBIOS 7 and 8) or the AMIBIOS version's initial release date (all other versions)
    • Note: Even on versions using the initial release date, this section was occasionally modified by the OEM to reflect the ROM release date instead.
  • DDDDDDDD: BIOS identifier (usually the chipset)
  • Project: internal BIOS project ID
    • Only used on later revisions of AMIBIOS 6 and later versions.
  • Y2KC: unknown, most likely Year 2000 compatibility indicator
  • K: Keyboard controller ID

Example string: 61-0530-001169-00101111-071595-440BX/ZX-1AAET006-R

This string is for a 05.30 version ("0530") 128 KB ("1")* size AMIBIOS 6 ROM ("071595", initial release date for AMIBIOS 6) for 686 architecture processors ("6") with Intel 440BX or ZX chipset ("440BX/ZX") and an AMIKEY '94 clone keyboard controller ("R") for project ID 1AAET006 of MSI ("1169").

*The BIOS ROM size is actually 256 KB in this specific case, the 128 KB size specified in the string is an error. This also means the string is not always fully accurate, although mostly is.

List of known codes for sections of the ROM identification string

Click "Expand" to view.

  1. ↑ https://www.intel.com/content/www/us/en/content-details/630266/removal-of-legacy-boot-support-for-intel-platforms-technical-advisory.html | Note: Although this document was published in 2023, it clearly mentions legacy boot being discontinued in 2020.
  2. ↑ https://twit.tv/shows/triangulation/episodes/226
  3. ↑ https://www.youtube.com/watch?v=5jYX3sL08Xs
  4. ↑ https://mrbios.com/techsupport/award/postcodes.htm | "AMI BIOS 2.2x" section
  5. ↑ https://mrbios.com/techsupport/award/postcodes.htm | "AMI Plus BIOS" section
  6. ↑ https://web.archive.org/web/19970623225759/http://www.amibios.com/amibios.html
  7. ↑ https://web.archive.org/web/19991012065711fw_/http://ami.com/amibios/bios.platforms.desktop.html
  8. ↑ https://web.archive.org/web/20000607010157fw_/http://www.ami.com/y2k_ami.html | "V.7.0" is listed as an AMIBIOS version, which must be 07.00.xx as 07.00.10 was not yet released at the time
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This page was last edited on 19 March 2025, at 06:53.