My Motherboard has 2 BIOS chips. Which one should I replace?

The hardware consists in two BIOS microcircuits application on the system
board and is named TwinBIOS. At failure of one microcircuit contents there
is a possibility of load from the second, and the realisation of the given
possibility is rather interesting. At usual switching on the system BIOS
number 1 is used, and if at pushing the button Power to hold the button
Reset, BIOS number 2 will be used.

If both microcircuits content is serviceable, it is possible to choose what
microcircuit to use for the load in BIOS configuration.
The program part consists of built-in in BIOS programs - Flash Utility and
HDD Instant Recovery Utility. The first allows to flash BIOS new versions
without usage any additional means: it is enough only to have a diskette
with the new version. And TwinBIOS technology is entirely supported by the
program: BIOS number 1 can be flashed both from a diskette and from number
2, but standby BIOS number 2 - only from a diskette. Such a range of
possibilities allows to experiment with new versions without any risks to
damage the system.

Also see Article 1043