System Management BIOS

In computing, the System Management BIOS (SMBIOS) specification defines data structures (and access methods) that can be used to read management information produced by the BIOS of a computer.[1] This eliminates the need for the operating system to probe hardware directly to discover what devices are present in the computer. The SMBIOS specification is produced by the Distributed Management Task Force (DMTF), a non-profit standards development organization. The DMTF estimates that two billion client and server systems implement SMBIOS.[2]

Not to be confused with DMI.
System Management BIOS
StatusPublished
Year started1999 (1999)
Latest version3.4.0
August 20, 2020 (2020-08-20)
OrganizationDistributed Management Task Force (DMTF)
Related standardsCommon Information Model (CIM), Web-Based Enterprise Management (WBEM), Redfish
DomainSystems management
AbbreviationSMBIOS
Websitewww.dmtf.org/standards/smbios

The DMTF released the version 3.4.0 of the specification on August 20, 2020.[3]

SMBIOS was originally known as Desktop Management BIOS (DMIBIOS), since it interacted with the Desktop Management Interface (DMI).[4]

History

Version 1 of the Desktop Management BIOS (DMIBIOS) specification was produced by Phoenix Technologies in or before 1996.

Version 2.0 of the Desktop Management BIOS specification was released on March 6, 1996 by American Megatrends (AMI), Award Software, Dell, Intel, Phoenix Technologies, and SystemSoft Corporation. It introduced 16-bit plug-and-play functions used to access the structures from Windows 95.[5]

The last version to be published directly by vendors was 2.3 on August 12, 1998. The authors were American Megatrends, Award Software, Compaq, Dell, Hewlett-Packard, Intel, International Business Machines (IBM), Phoenix Technologies, and SystemSoft Corporation.

Circa 1999, the Distributed Management Task Force (DMTF) took ownership of the specification. The first version published by the DMTF was 2.3.1 on March 16, 1999. At approximately the same time Microsoft started to require that OEMs and BIOS vendors support the interface/data-set in order to have Microsoft certification.

Version 3.0.0, introduced in February 2015, added a 64-bit entry point, which can coexist with the previously defined 32-bit entry point.

Version 3.4.0 was released in August 2020.[6]

Contents

The SMBIOS table consists in an entry point (two types are defined, 32-bit and 64-bit), and a variable number of structures that describe platform components and features. These structures are occasionally referred to as "tables" or "records" in third-party documentation.

Structure types

As of version 3.3.0, the SMBIOS specification defines the following structure types:[7][8]

Accessing SMBIOS data

The EFI configuration table (EFI_CONFIGURATION_TABLE) contains entries pointing to the SMBIOS 2 and/or SMBIOS 3 tables.[9] There are several ways to access the data, depending on the platform and operating system.

From UEFI

In the UEFI Shell, the SmbiosView command can retrieve and display the SMBIOS data.[10][11] One can often enter the UEFI shell by entering the BIOS, and then selecting the shell as a boot option (as opposed to a DVD drive or hard drive).

From Linux

The Linux kernel contains an SMBIOS decoder, allowing systems administrators to inspect system hardware configuration and to enable or disable certain workarounds for problems with specific systems, based on the provided SMBIOS information.

The userspace command-line utility dmidecode(8) inspects this data. Information provided by this utility typically includes the system manufacturer, model name, serial number, BIOS version and asset tag, as well other details of varying level of interest and reliability, depending on the system manufacturer. The information often includes usage status for the CPU sockets, expansion slots (including AGP, PCI and ISA) and memory module slots, and the list of I/O ports (including serial, parallel and USB).[12][13] Decoded DMI tables for various computer models are collected in a public GitHub repository.[14]

For Dell systems there is a libsmbios utility.[15]

From Windows

Microsoft specifies WMI as the preferred mechanism for accessing SMBIOS information from Microsoft Windows.[16][17]

On Windows systems that support it (XP and later), some SMBIOS information can be viewed with either the WMIC utility with 'BIOS'/'MEMORYCHIP'/'BASEBOARD' and similar parameters, or by looking in the Windows Registry under HKLM\HARDWARE\DESCRIPTION\System.

Various software utilities can retrieve raw SMBIOS data, including FirmwareTablesView[18] and AIDA64.

Generating SMBIOS data

Table and structure creation is normally up to the system firmware/BIOS. The UEFI Platform Initialization (PI) specification includes an SMBIOS protocol (EFI_SMBIOS_PROTOCOL) that allows components to submit SMBIOS structures for inclusion, and enables the producer to create the SMBIOS table for a platform.[19]

Platform virtualization software can also generate SMBIOS tables for use inside VMs, for instance QEMU.[20]

If the SMBIOS data is not generated and filled correctly then the machine may behave unexpectedly. For example, a Mini PC that advertises Chassis Information | Type = Tablet may behave unexpectedly using Linux. A desktop manager like GNOME will attempt to monitor a non-existent battery and shutdown the screen and network interfaces when the missing battery drops below a threshold. Additionally, if the Chassis Information | Manufacturer is not filled in correctly then work-arounds for the incorrect Type = Tablet problem cannot be applied.[21]

See also

References
  1. "Libsmbios Library Documentation". dell.com. 2007-04-11. Archived from the original on 2016-09-18. Retrieved 2016-02-02.
  2. DMTF press release on SMBIOS 3.2: https://www.dmtf.org/content/dmtf-releases-smbios-32
  3. "System Management BIOS". dmtf.org. Sep 2018. Retrieved 2019-12-30.
  4. "Desktop Management BIOS Specification, Version 2.0" (PDF). uni-regensburg.de. 1996-03-06. Retrieved 2016-02-02.
  5. "Desktop Management BIOS Specification, Version 2.0" (PDF). uni-regensburg.de. 1996-03-06. Retrieved 2016-02-02.
  6. All Published Versions of DSP0134
  7. Ken Hess (2010-04-23). "Linux System Information Decoded". linux-mag.com. Retrieved 2016-02-02.
  8. SMBIOS Specification, version 3.3.0, Sep 2019, https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.3.0.pdf
  9. UEFI Specification, version 2.6, section 4.6
  10. "smbiosview (HP UEFI System Utilities and Shell Command Mobile Help for HP ProLiant Gen9 Servers)". hp.com. 2015-09-22. Retrieved 2016-02-02.
  11. "Tianocore /edk2/ShellPkg/Library/UefiShellDebug1CommandsLib/SmbiosView". sourceforge.net. Retrieved 2015-01-27.
  12. "dmidecode". nongnu.org. Retrieved 2013-10-30.
  13. Joe Barr (2004-11-29). "dmidecode: What's it good for?". linux.com. Retrieved 2013-10-30.
  14. Linux Hardware Project (2019-12-24). "Large collection of decoded DMI tables for various computer models". linuxhw. Retrieved 2019-12-24.
  15. Dell (2021-01-19). "libsmbios provides a library to interface with the SMBIOS tables. It also provides extensions for proprietary methods of interfacing with Dell specific SMBIOS tables". Dell. Retrieved 2021-01-19.
  16. wjfrancis (2008-03-27). "SMBIOS Peek - CodeProject". Codeproject.com. Retrieved 2012-05-12.
  17. SMBIOS Support in Windows, Microsoft paper, updated April 25, 2005
  18. "FirmwareTablesView". NirSoft. Retrieved 2020-12-02.
  19. Platform Initialization Specification, volume 5, section 6, SMBIOS Protocol
  20. QEMU version 2.12.50 User Documentation, https://qemu.weilnetz.de/doc/qemu-doc.html
  21. "5 to 20 minutes shutdowns on Cherry Trail machine". Red Hat Issue Tracker. March 21, 2019. Retrieved March 21, 2019.
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