Laptop + ENB = unexpectedly large frame drop

[cordate]

I've been messing about with Skyrim on a laptop for the first time and I'm not sure the results I am getting are typical. 

 

Lappy stats:

Windows 10

NVidia 960M

RAM: 8Gb

Processor: i5-6300HQ Quad-core @ 2.3GHz

Resolution: 1920 x 1080 (framerates are marginally better if I run it fullscreen)

Skyrim: Original edition

Mods running: STEP base 

 

Without an ENB running, I can get framerates in the mid 70's in my interior test cell -not that one wants to actually play with anything above 60, given the physics issues.

 

But with an ENB running (I've tried 4 or 5 and they all seem to give about the same performance hit), the framerate goes down to about 23FPS, and turning off shadows, DoF, and Ambient Occlusion only gives me about 6 additional FPS. 

 

I'd expect to lose maybe about a third of my framerate running an ENB that my machine found demanding, but this is more like 70%.

 

I've tried loading an unmodded game session and got similar framerates, so my STEP base install doesn't appear to be causing issues.

 

I've checked task manager while running the game and the memory and CPU are only lightly tasked - memory gets about 50% used and the CPU's under 25%. I'm going to install the Skyrim Performance Monitor next and see if I can glean any clues from it. Maybe the video card's getting hot and throttled back.

 

Maybe someone else here has already worked through similar troubles? Or is a 70% framerate hit just a thing that happens on some laptops? 

 

I've tried loading an unmodded game session and got similar framerates, so my STEP base install doesn't appear to be causing issues.