i was looking at old tutorials and it says press the sector button where did they put it and/or what is it now it was by the prop(isnt there) and actor buttons in the realtime menu
sectors disappeared with blender 2.12 iirc
they were able to give a good speedup though, try level3.blend [I think] in the 2.03 demos in blender 2.03 and 2.23 to see what I mean.
2.04 release: http://download.blender.org/release/Blender2.04/
the file I mention is level_2.blend in demo20.zip
keys: left arrow, right arrow [turn]
numberpad 4, 2, fwd / backwards
compare its speed [and what it looks like in wireframe] in blender versions (2.00 to 2.10 I guess, 2.04 works) to the current version [or 2.25 or 2.23…]