Using the BIOS to identify a motherboard

Under normal conditions each and every mainboard model or model family uses a unique BIOS. This is a geeky way of saying that the BIOS used on most mainboards was written or modified specifically for that board type. It is for this reason that you will notice so many different BIOS update files on most manufacturers’ websites. If a company produces fifteen different mainboard families, there will generally be at least fifteen different BIOS versions used across that mix. Sometimes, different BIOS versions will be used within a mainboard family as well. Consider two boards within a given design family, one with two DIMM slots and supporting up to 512MB of SDRAM, while the other has three DIMM slots and supports 768 MB of SDRAM. A likely consequence of this design change is that these two boards, while in the same design family, will probably use different BIOS versions.

Don’t be confused by the terminology here, either. The terms version and release have two distinct meanings as applied to PC mainboard BIOS. Version is generally taken to mean a BIOS that is designed for a specific combination of processor, RAM, chipset, peripheral support, OS support, and performance level. Release is generally taken to mean a specific iteration of a specific BIOS version. Various BIOS versions are offered in various releases as bug fixes or additional system enhancements become available. Some websites will refer to their BIOS update offerings by mainboard model and BIOS version. In this case, the mainboard model correlates to the actual BIOS version, while the update version correlates to the BIOS version release.


Now that that is out of the way, why is it important to begin with? It’s like this – if each different mobo uses a unique BIOS, it stands to reason that the mobo can then be identified simply by identifying the BIOS that it uses. Some manufacturers make this very easy for us by displaying the BIOS version and release on system startup. Others will display a BIOS identifier string on startup, while still others will offer no on-screen clues. Lets consider an easy one first.




Figure 2 – Mainboard ID information displayed on startup
Figure 2 shows the information displayed at the upper left corner of the monitor on system startup, during the RAM count. Figure 3 shows the BIOS ID string (for the same mainboard) that is displayed at the same time. To keep this information displayed long enough to write it down, simply press the Pause key on your keyboard when the information appears. Write down the desired information, and then press any key to continue the boot cycle.

In Figure 2, the board is identified with the string TRM-P6L40A4-V1.02, and the BIOS used is some iteration of Award’s 4.51PG BIOS – probably the most popular PNP BIOS in use today. Using the board ID string as a basis, a simple web search takes us to http://support.tekramusa.com, the support site provided by the board maker, Tekram Technology.

The board ID string also tells us that the current BIOS release is v1.02. Is this information relevant? The answer to that depends upon the reason you are trying to ID the board in the first place. Suppose you are having a problem getting a real-mode CD-ROM device driver (for your BTC CD-ROM reader) to load successfully. Somewhere along the line, somebody says, “Yeah – that was a problem with that mobo with early BIOS releases. They fixed that in release 1.03.” Now it’s obvious, right?

That’s all the information that we need to identify this particular board. It actually identified itself and its BIOS release for us. Now suppose that we are dealing with a board that doesn’t display the board ID info, but does display the BIOS ID string across the lower portion of the monitor, as shown in Figure 3 below. Can we use this information to work backwards to the board model? Sometimes … as we are about to see.





Figure 3 – BIOS ID string displayed on startup
A quick look at the BIOS ID string gives us some helpful info right off the top. We can see that the BIOS date here is 10/29/97, and that the BIOS provides support for the Intel 440LX/Winbond W877AF chipset. The BIOS string also gives us some other useful info if you know where to look for it. I have found Wim’s BIOS Site – http://www.wimsbios.com – to be an excellent resource for identifying the board from its BIOS ID string. This site has extensive listings for both AMI (American Megatrends) and Award BIOS’es, and there is also a wealth of other BIOS-related information available there as well.

As is thoroughly explained at Wim’s BIOS Site, the significant portion of the string is the 2A69JTG9C portion, which includes a basic chipset code, a manufacturer code, and a model/family code. The following illustrations show how these codes relate in the tables provided at the site. As is evident in Figure 5, where available, there are also links provided to the board maker’s website.





Figure 4 – BIOS chipset code in ID string 2A69JTG9C



Figure 5 – Manufacturer codes as referenced in ID strings




Figure 6 – Manufacturer and board family or model codes in ID string 2A69JTG9C
A similar scheme of ID codes is used by AMI in their BIOS’es. I have a 533MHz test box in my shop that reports a BIOS ID string of 62-0922-009999-00101111-071595-000000-M756LMR-H and a displayed date of 09/22/2000. In most cases, the last four digits in the third group are the manufacturer code. Note that I said “in most cases”. This particular board is a PC-Chips board, and their assigned ID is 1437. There is no apparent pattern to the use of 9999 in the ID string, and I have seen it on several different makers’ boards. This ID string does, however, include the board model, M756LMR, in its last group of digits. AMI calls this a Project Tag. Again there is no fixed rule to this. Some mobo’s display their chipset type as the sixth group of digits, where this string shows all zeroes. What I have seen is that when the manufacturer ID is shown as 9999, the ID string will often contain the model as a project tag, and when the ID string has a valid maker ID, it then usually has a chipset type rather than a model displayed. In the case of this mobo, a web search for the Project Tag data yielded the manufacturer’s name.