I've noticed a very high performance impact during large land battles when Unit Detail is set to High or Ultra and I was hoping someone could shed some light as to what in my rig may be causing this apparent bottleneck.
To illustrate the issue I set all GFX settings to Low/Off except Unit Detail which was left on Ultra. During a replay of a large siege battle my FPS would drop to 25-35 once the armies collide on the walls. In contrast when I set all the settings to Max/On (even VSync) but set Unit Detail to Low the absolute minimum frames I could get was 33 FPS.
Why is it that just this one setting can cripple my rig?
Additionally I also ran GPU-Z and Perfmon in the background and found that, even though my FPS was dropping below 30 during the first test, the maximum load on my GPU was 43% with a mere 540 MB VRAM used (of 1280).
The interesting thing though was my CPU usage. It appeared that one core was sitting between 95-100% usage whilst the rest were below 20% (some were even in a parked state).
Clearly the game isn't taxing my PC so why am I getting below 30 FPS?
Is there anything I can do to run High Unit detail without it crippling my experience?
Core i7 K 875 (OC to ~3300GHz)
GeForce GTX 570 (1280MB)
8 GB DDR3 RAM (PC3-16000)
I've already updated all drivers so no need to suggest that
TL;DR: High/Ultra Unit Detail cripples my FPS even though CPU & GPU load is low.