I am unsure if that is still the case but the BIOS was always stored on the CMOS, in theory your computer cant boot without it.
the cmos is just volatile memory (though cmos is technically a type of semiconductor which can be made to do many different things, doesnt really describe what the chip really is, which i believe is an sram, ****ing misnomers), hence the battery, used to store settings for the bios, which (i think) is on an entirely different chip (likely an eeprom). you can boot without it but it will be like booting a mobo with factory settings every time. this isnt so much of a problem as it used to be, as most hardware tends to auto configure its self just fine. back in the old days when you needed to enter your hd parameters for them to work, and if you had a bad battery or cmos, you would have had to fiddle with the bois each time you booted. these days you might have issue with memory settings, but it usually defaults to a safe but lower performance setting. if your battery is dead (ive never had a mobo that lasted longer than its battery), you can order a dozen of them from china for a buck. if your cmos is bad, i bet you could get another chip off of ebay. why we dont store settings on something like flash or eeprom is beyond me. limited write cycles, yes, but how many times do you configure a bios? i think some mobos have such features though.
axe that, i decided id look it up.
there is an sram for bios settings but its usually integrated into the southbridge, along with the real time clock. sram is used for its low idle power consumption. the battery keeps the clock ticking and the ram in standby. the bios itself is stored on another chip (usually flash but eeproms may still be used, since they offer 10x more write cycles). so the chip by the battery is the rom and not the ram. of course this depends all on manufacturer preference.
