Your computer is getting too hot, when you run 3dmark06, the temps of your GPU (graphics card) start to rise. Once it gets to 95*C, it clocks down your computer to 800MHz to prevent from over heating. Download i9kfangui, or nVtemplogger to track your temperatures when your running 3Dmark. This happens to my computer when I run 3dmark as well, but doesnt lag in games.
Theres a few things you can do...
1) Make sure your computer has enough air flow underneath it. Prop the back end up a bit with 2 plastic bottle caps or something of the sort.
2) Blow your computer out. Dust is a big problem when it comes to our lappies. Mine dropped a few degrees after I did that.
3) Apply Arctic Silver 5 (AS5) to your GPU to drop the speeds.
Good luck with your temps!
-Casanova
