In any of the HSC standard scenarios, my average frame rate is around 30 fps. This is with everything on "high" except shadows, which are on "low". It fluctuates very little (26-32 fps).
The issue is I'll have periods of about 30 seconds where the frame rate dips down below 14 fps. Sometimes way below. Then seemingly without a reason, it goes back up to 30 fps, Instantly. I've paid attention to AI, scenery loading times, etc. There seems to be no connection to AI trains. Scenery loading doesnt specifically seem to be associated with the slow downs either. It's not like most games where a slow down is gradual or clearly associated with an increased graphics load.
Then, after a period of these while running a scenario, I exited TS2012 and looked at my GPU and CPU meter (Win 7 Sidebar). It showed a 'map' of the slowdowns, if you will. And what it shows is rather shocking. When framerates are at 30fps and life is good, GPU load is around 90-100%. When the framerates slow way down, it reflects this in the GPU graph by showing the load go from 100% to about 30%, instantly. I thought maybe it was due to temperatures getting too high, but from what I can tell, GPU temps never exceed 55 degrees C.
Image of the sidebar immediately after exiting TS2012:

Throughout all this, the CPU graph show both my cores at a constant 60-70% load and around 70 degrees C (TjMax for my i5 is 105C). So I'm really confused.
I thought maybe it was hard drive speeds (I have two at 7200 RPM). But it doesnt make sense why other games arent having these issues. I then thought maybe I should move my paging file to the non OS drive. I did it, but this too has had no effect on eliminating the slowdowns. Also, these issues pop up regardless of graphics settings. They can be at low or high, TSX or no TSX, and it still happens.
Anyone have a clue whats going on? Is anyone else experiencing this? Like I said, this never happened with RW-2, or any other game.
System:
TOSHIBA - Model Qosmio X505
Processor Intel® Core™ i5-430M processor @ 2.26 GHz (2.53 GHz with Turbo Boost Technology), 3MB L3
Cache
Memory G-Skill RAM 8.00 GB DDR3 (CL 7-7-7-20)
Graphics NVIDIA GeForce GTS 360M with 1GB GDDR5
Total available graphics memory (incl. shared) 4095 MB
Hard Drive 2x 500GB Hitachi (7200rpm) Serial ATA
1gb Paging File on OS HDD, 12gb Paging File on 2nd HDD
OS Windows 7 Home Premium 64 bit