Laggy GPU?

Sorry if this was already addressed and feel free to link a thread that addresses this problem, but recently my video graphics card isn't what it used to be. Games that I could run smoothly are fine most of the time but every once in awhile it would stutter. Specifically, a game that I used to be able to run at 60+ fps now runs at 20-35 fps. Not sure if Binding of Isaac is a CPU-reliant or GPU-reliant game, but it's very slow and laggy, as opposed to running relatively fast even at the highest settings. If you need clarification on anything or help in any way, let me know please

System: Alienware m17x R2
OS: Windows 7 Ultimate 64-bit
BIOS: Ver A10 1.00
CPU: i7 920x
GPU: ATI Mobility Radeon HD 5870 running in crossfire

 

how are your temps? Could you have dust in the fans that could be getting your CPU/GPU's to hot?

 

As tony says, you should start by checking your temps.

Also, have you updated drivers recently?

 

Alright, I used GPU-Z and it runs 45-50 idle, and min of 60 and max of 75 while I'm playing the game (frame drops to 20ish when it's max). My CPU ran ~50 at all times, whether it was idle or during the game.

I'm not sure when I updated my drivers but I remember downloading the A10 bios when it came out ~6 months ago.

 

Simple tell tale sign that your 5870's are being throttled once they hit that 75C threshold. Are you currently using a notebook cooler to supply better airflow to the R2? We also normally avoid the newer BIOS versions as Dell tweaked the throttling settings to kick in at lower temperatures.

 

I'm using a NZXT Cryo LX Cooler atm. Is it too late to downgrade or is there an alternative?

 

You could go with a single 6990M, which has a 256 Bit memory BUS and keep the same performance. You could take on the task of redoing the thermal paste on the GPU's.