On default settings L3DT uses all the CPU power it can get. This makes your windows sluggish and almost impossible to use.
You can tweak L3DT by going Utilities → Throttle CPU and put that to about %50 and Settings → Multi-Thread settings, tick Core count manual override and put it at least one lower than the amount of cores you have. Like 4 core system put in 3.
Now your L3DT attributes and textures processing does not cause your windows to get sluggish and other programs work fine.
L3DT is much slower on processing this way, so lets say in our computer 20480 res textures computed in 2hrs with default/full settings while on the suggested settings here its 4hrs. If you look at the times and say no thanks, consider that with full settings your windows is pretty much unusable for that 2hrs amount…