BIOS Checksum Error: It’s Not That Bad!

A BIOS checksum error is one of the most common errors you can encounter when you build your own computer, perform a hardware upgrade or attempt to bring back to life a computer that hasn’t been used for a long time. If it sounds like a scenario that’s not very likely to happen to you, think again, as computers became so un-complicated that you don’t need to be working at NASA to know how to upgrade or even build one yourself; in fact, learning how to build your own computer is as simple as taking this online course, so the possibility of coming across a BIOS checksum error one day is higher than you think. The error indicates that the BIOS is incorrectly configured or corrupted, preventing the computer from booting normally; unlike operating system errors or software errors that occur after your computer is up and running, a BIOS checksum error will render it inoperable right after you power it on, so it’s no wonder this type of error can seem like something really serious. Fortunately, it is not as scary as it seems, and fixing it is quite easy.

BIOS Basics

In order to understand what triggers the BIOS checksum error, what the error means and how you can fix it, it is necessary to understand what the BIOS is and how it works. Simply put, the Basic Input/Output System, or BIOS, is a program that checks if all the components necessary for the computer to run are present; if everything is ok, the BIOS gives the processor the necessary instructions on how to proceed and load the operating system.

Before the boot code in the BIOS is executed, though, the BIOS data is checked for authenticity by comparing one of its values, known as a checksum, against a value stored in a memory chip called CMOS; if the values match, it means that everything is working correctly, so the boot code is executed and the computer starts normally. However, if the checksums do not match, it means that something interfered with the BIOS, so the computer displays a BIOS checksum error and stops the boot process.

Causes of BIOS Checksum Errors

There are two scenarios that can trigger a BIOS checksum error:

• Something interacts with the BIOS code and interferes with the checksum it generates;
• Something alters the pre-defined checksum values present in the CMOS memory.

The first scenario usually occurs when an incompatible piece of hardware is installed, as it will fail to pass the initial hardware check performed by the BIOS, and thus return a BIOS checksum error. A BIOS checksum error can also be generated by an incorrectly performed overclocking process. In case you are not familiar with this, overclocking is a process which implies modifying some parameters of certain components to higher values in order to obtain increased performance. Pushing the components too hard will usually trigger their protection systems, which will make the components unusable until you return them to their default settings. Just as in the case of incompatible hardware, components that have the protection systems activated will generate an invalid BIOS checksum, thus leading to the apparition of the BIOS checksum error.

Even if the generated BIOS checksum is correct, a BIOS checksum error can still appear if the checksum it is verified against is invalid. This value is stored in a CMOS memory chip which requires continuous power to function. The power is usually provided by the PC’s power supply, but a small battery is also present to help preserve the settings when the PC is unplugged. If the PC is not in use for longer periods, the power in the battery will eventually run out, thus altering the values stored in the CMOS chip. These settings can also become corrupted if you attempt to perform a BIOS update with an incompatible BIOS file, as this operation implies the rewrite of the data stored in the CMOS memory chip. This wasn’t a real problem in the past, as CMOS chips were very difficult to program, but as technology advances, updating a BIOS became a very simple operation. If you are passionate about programming and want to learn about hardware-level programming, check out this online course on PLC programming to ease your way into programming your own BIOS for logic controllers. Once you figure out the programming part, you may be interested in taking things even further by taking an online course to learn how to create your own circuit boards, for a truly customized device.

Fixing a BIOS Checksum Error

The first thing you need to do in order to fix a BIOS checksum error is to determine its cause, and if you’ve read the previous paragraph, you should already have a pretty good idea what triggered the error. In most cases, fixing a BIOS checksum error is a straightforward process that only takes a few minutes to complete.

• Dead Battery

Fixing this is a no-brainer: you take out the old battery and replace it with new one. The CR2032 is the most common model of CMOS batteries, but just to be on the safe side check the model on the old battery before putting the new one in, to make sure it’s the same.

• Incorrect BIOS/CMOS Settings

Whether your CMOS settings got corrupted after a long period of no use or you messed up the BIOS settings yourself, bringing them to their defaults is quite easy. Simply access the BIOS and select the “Load Defaults” option. If your BIOS is not accessible anymore, you can perform a hardware reset by using the “Clear CMOS” jumper on the motherboard. Refer to your motherboard’s manual for instructions on how to perform this operation. There’s also a third way to reset the BIOS settings: unplug your computer, remove the CMOS battery and simply wait a few minutes for the CMOS chip to remain completely unpowered; this will bring it to the default settings.

• Unsuccessful Upgrade

If you come across a BIOS checksum error as a result of an upgrade that went wrong, try removing the newly installed components and testing them in a different machine to see if they all function correctly. You can also test the components in the computer you want to upgrade by installing one component at a time and see if the machine works correctly. Once you identify which component is the trouble maker, you can either replace it with another component or remove it from the upgrade plan.

Moving Forward

Ok, so you just learned how to fix the not-so-dreadful BIOS checksum error, but what about all the other problems you might encounter while building or upgrading a PC? Check out Joe Lowmiller’s article on building your own computer for interesting tips and tricks that might save you from some serious headaches. If you found Joe’s article interesting, and I’m sure you did, you might just get an appetite for building things, so why not take an online course to learn to build and program an Arduino platform?