Yoma, Chapter Four, Mishnah Six
The final mishnah of the chapter continues to deal with differences between Yom Kippur and other days.
On other days there were four wood-piles there, but on this day five, the words of Rabbi Meir.
Rabbi Yose says: on other days three, but on this day four.
Rabbi Judah says: on other days two, but on this day three.
The topic of this mishnah is how many piles of burning wood were on the outer altar on normal days and on Yom Kippur as well.
Rabbi Meir holds that there were normally four wood-piles. The Talmud explains that each pile had its own function. The first was a large pile on which the tamid and its remnants were offered. The second was the pile from which cinders were taken to burn the daily incense offering. The third was to keep an eternal flame (see Leviticus 6:5). The fourth was to burn the limbs of sacrifices that they had not succeeded in burning during the night. On Yom Kippur they added one more wood-pile from which the high priest would collect the cinders to burn the special incense which he will bring into the Holy of Holies.
Rabbi Yose holds that there was no special wood-pile for the limbs that had not been burned during the night.
Rabbi Judah holds that there wasnt a special wood-pile to preserve an eternal flame. Evidently, the other wood-piles were sufficient to ensure that there would always be a flame.