tailieunhanh - Handbook Phần Cứng PU part 27

Tham khảo tài liệu 'handbook phần cứng pu part 27', công nghệ thông tin, phần cứng phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | ROM with BIOS BIOS is sometimes called firmware. Before 1990 or so BIOSes were held on ROM chips that could not be altered. As their complexity and need for updates grew BIOS firmware was stored on EEPROM or flash memory devices. This EEPROM chip sits on a FWH interface but in some newer boards EEPROM chips are already sitting on a newer emerging interface named SPI. EEPROM chips are advantageous because they can easily be updated by the user however an improperly executed or aborted BIOS update can render the computer or device unusable. To avoid BIOS corruption some new motherboards have a backup BIOS Dual BIOS boards . Also most BIOSes have a boot block which is a portion of the ROM that runs first and is not updateable. This code will verify that the rest of the BIOS is intact via checksum hash etc. before jumping to it. If the boot block detects that the main BIOS is corrupt then it will typically boot to a floppy so that the user can try flashing again hopefully with a better image. Hardware manufacturers frequently issue BIOS updates to upgrade their products and remove bugs. edit Firmware on adapter cards A computer system can contain several BIOS firmware chips. The motherboard BIOS typically contains code to access fundamental hardware components such as the keyboard floppy drives ATA IDE hard disk controllers USB human interfaces and storage devices. In addition plug-in adapter cards such as SCSI RAID Network interface cards and video boards often include their own BIOS complementing or replacing the system BIOS code for the given component. In some devices that can be used by add-in adapters and actually directly integrated on the motherboard the add-in ROM may also be stored as separate code on the main BIOS flash chip. It may then be possible to upgrade this add-in BIOS sometimes called an option ROM separately from the main BIOS code. Add-in cards usually only require such an add-in BIOS if they Need to be used prior to the time that the operating .