Not all of us mate! Some of us benchmark before and after.
Yeah at some point a long time ago, I tried it, found it helped somehow,
can't really remember, and then just always set up new systems like that
until the Radeon and Catalysts came along.
If the setting hadn't been working fine with my nVidia cards for years
and all my benchmarks hadn't seemed as good as anyone elses, I would
have changed it before getting a Radeon. As soon as I got a Radeon I
changed the setting.
Almost all of the tweak programs or sites where I've seen the Large
System Cache setting listed, pretty much say, "give it a try, see if it
helps your system, no guarantees." Until the Radeons/Catalysts started
having catastrophic(for some?) problems with the setting it wasn't too
big of a deal either way.