Across the full range of modern computers BIOS is stored on the microcircuit on the basis of Flash Memory. Such microcircuit can be flashed with the assistance of specific programs outright on the computer. The record of the new BIOS version is usually called reflash. This operation may become necessary for addition of some new functions to the BIOS code, faults correction or replacing corrupted versions.
For most cases Flash Memory is installed on the specific board (pic. 2.1) that allows to replace the microcircuit easily when necessary.
Pic. 2.1. Examples of BIOS microcircuits installation on the mainboard.
BIOS microcircuits happened to be set on the rectangular case DIP32 (pic. 2.1, on the left) on the out-of-date computers; BIOS microcircuits on square case are used on majority of boards (pic. 2.1, in the middle), and tiny circuits with the serial interface can be found on the new boards (pic. 2.1, on the right).
Usually they are presented with the chip sticker with the reference to BIOS version. Otherwise, if there is no label – Flash Memory circuit marking is provided. BIOS uses configuration parameters which are stored in specific CMOS-memory. It received its name according to the technology of circuits manufacturing where Complementary Metal-Oxide Semiconductor was applied. CMOS-memory is energized from the specific battery set on the mainboard that is also used for energizing real-time clock.