I usually don't notice slowness with change blending mode if invalid for video card
Usually, for me I experience slowness, ONLY if the following:
I don't change the CF to 3 in Perfect Dark and the CF to 1 in Harvest Moon 64,using "Protect Memory" in The Legend of Zelda Ocarina of Time and/or using sort independent anti-aliasing.
I don't notice any slowness with anisotrophic filtering.
WARNING, IT WILL BE VERY SLOW (SLLLOWWW)
IF THE FOLLOWING:
CPU core set to interpreter
and/or
using frame buffers except for "Emulate Clear"
or "Black":!!!: