PRAM has been with Mac from the beginning. it has been used to keep the time zone, startup volume and speaker volume. Resetting of the PRAM thus required resetting the computers time. Mac OS X stores even more in PRAM, such as kernel panic information. This Apple Care article describes what Mac OS X stores in PRAM.
Resetting your Mac’s PRAM and NVRAM
If unable to reset the clock in an older Mac, it may indicate a PRAM battery change is necessary. This list has the Mac and battery part number.