Flash BIOS

To facilitate BIOS upgrades, many PC makers have shifted to using Flash ROM chips for their BIOS code instead of EPROM. You can upgrade a system equipped with such a Flash BIOS as easily as running a single program that writes updated code to the Flash ROM chips.

Some PC makers use Flash ROM chips to store their BIOS simply because they can encode the BIOS program more quickly into Flash ROM than EPROM. To make the BIOS flash-upgradable, however, your PC's motherboard requires special circuitry to apply the programming voltages to Flash ROM chips. Not all PCs using Flash ROM for BIOS storage have the necessary circuitry. You should check your PC's owner's manual to determine whether the Flash ROM in your system is software upgradable.

Updating a flash BIOS usually involves two files, a binary file that contains the actual BIOS code and a special program called a loader. The loader activates the motherboard circuitry required to write to the BIOS chips, then transfers the contents of the binary BIOS file to the chips. The loader's job is one of the most delicate in the operation of a PC because if it makes a mistake, your system may be rendered inoperable. It might not be able to boot up and re-run the loader. Consequently, for your security, some system makers require that you take elaborate precautions before you try making a BIOS upgrade. For example, the manufacturer may require you to use both the battery and AC power supplies of a notebook PC to make a BIOS update.

To prevent a BIOS upgrade from accidentally rendering your PC inoperable, many PCs include boot block protection. This feature simply protects or prevents the block of the Flash ROM used for the essential boot up code-the code necessary to read a floppy disk but not necessarily any other support or even diagnostics-from being erased during the upgrade. The protected code is sufficient to get your floppy going so that you can try upgrading your BIOS once again-or if the new BIOS itself is the problem, restore your old BIOS.

Because motherboard circuitry varies among different computer brands and models, the BIOS loader made for one system may not work with another. Unless you're advised otherwise by your PC's manufacturer or a BIOS maker, you should assume that you need a matched pair of files-the BIOS code and loader-to make a BIOS upgrade. In general a loader will warn you if it is not meant for your particular system, but don't depend on such a warning to avoid incompatibilities. A loader that makes a mistake can mean your PC must go back to the factory for new BIOS chips before it will boot again.

Along with fixing problems, upgrading a flash BIOS can sometimes cause them. BIOS makers usually design their flash BIOS loaders to reset your PC's setup parameters to the factory defaults so your system gets a fresh start with its new BIOS. If you've customized your system before making the upgrade (for example, adjusting the energy conservation options of a notebook machine), you'll have to re-establish your settings after the upgrade. Sometimes you may find that the load process has altered the date set in CMOS. Operating your system without checking and resetting the date can cause problems with programs sensitive to the relationship between the current time and file date codes. For example, your backup system or disk maintenance program may not work properly after you upgrade your BIOS if you don't properly restore your system clock.