▁some ▁believe ▁that ▁CPU s ▁and ▁GPU s ▁will ▁conver ge ▁one ▁way ▁or ▁another ▁and ▁the ▁line ▁between ▁software ▁and ▁hardware ▁rendering ▁will ▁fade . ▁ ▁Software ▁fall back ▁For ▁various ▁reasons ▁such ▁as ▁hardware ▁failure , ▁broken ▁drivers , ▁em ulation , ▁quality ▁ass urance , ▁software ▁programming , ▁hardware ▁design , ▁and ▁hardware ▁limitations , ▁it ▁is ▁sometimes ▁useful ▁to ▁let ▁the ▁CPU ▁assume ▁some ▁or ▁all ▁functions ▁in ▁a ▁graphics ▁pipeline . ▁ ▁As ▁a ▁result , ▁there ▁are ▁a ▁number ▁of ▁general - pur pose ▁software ▁packages ▁capable ▁of ▁replacing ▁or ▁augment ing ▁an ▁existing ▁hardware ▁graph ical ▁acceler ator , ▁including : ▁ ▁R AD ▁Game ▁Tools ' ▁P ix om atic , ▁sold ▁as ▁middle ware ▁intended ▁for ▁static ▁linking ▁inside ▁D 3 D ▁ 7 – 9 ▁client ▁software . ▁ ▁Swift Sh ader , ▁a ▁library ▁sold ▁as ▁middle ware ▁intended ▁for ▁bund ling ▁with ▁D 3 D 9 ▁& ▁OpenGL ▁ES ▁ 2 ▁client ▁software . ▁ ▁The ▁sw r ast , ▁soft pipe , ▁& ▁LL VM pipe ▁render ers ▁inside ▁M esa ▁work ▁as ▁a ▁sh im ▁at ▁the ▁system ▁level ▁to ▁em ulate ▁an ▁OpenGL ▁ 1 . 4 – 3 . 2 ▁hardware ▁device . ▁ ▁W AR P , ▁provided ▁since ▁Windows ▁V ista ▁by ▁Microsoft , ▁which ▁works ▁at ▁the ▁system ▁level ▁to ▁provide ▁fast ▁D 3 D ▁ 9 . 1 ▁and ▁above ▁em ulation . ▁This ▁is ▁in ▁addition ▁to ▁the ▁extremely ▁slow ▁software -