Low fps maps and radeon videocards

On some maps (like kz_cg_holodeck, kz_man_dreaming, kz_a2_corruo_bhop etc) radeon owners have massive fps drops (on some parts of maps). On old cs client it was possible to avoid fps-drops using d3d video mode. But it new cs version valve removed this.
So how is it possible to fix those annoying fps-drops? (w/o installing old cs client ofc). Maybe some console commands, cvars, whatever?