page 179

"If list continuation processing is performed through the TA_LIST_CONT
register, the TA initializes its internal status in the same manner as
before, but leaves the TA_NEXT_OPB register unchanged."

TA_NEXT_OPB is only used in the case where the TA needs to allocate a
object pointer in a tile that has a full OPB (e.g: for TA_ALLOC_CTRL
0x2, to write the 16th opaque object to a tile, the next OPB for that
tile is at the address TA_NEXT_OPB).