Prime Perm maps were categorized as P2, previously ran in normal rooms and had a standard duration of 2 minutes.
When the map editor was first introduced (V0.63), normal rooms only played two map categories: the original maps made by Tigrounette and user-made maps (P0). As people started to make maps, the category of user-made maps became massive. And of course, some maps were better than the others. At this point P1 was introduced, to keep the better maps in the rotation for a longer period and also to give them more playtime. Soon came P2, which was the crème de la crème of the P1 maps. And soon P2 was split into P4 (shaman), P5 (art), P6 (mechanism), P7 (no shaman), P8 (dual shaman) and P9 (miscellaneous).