Hi, there, It's a number of factors for the jumping FPS, including: Where your current location in sim is, what page in the FMS you're on, and whether your displays are on. The Q6600 is a relatively decent CPU, but using the older tech in comparison to those like Sandy Bridge. The biggest bottleneck here is likely to be the CPU itself. As a tip, try and stay off the LEGs page while in flight on your FMC unless you're actually using it. This can eliminate some stutter if you're experiencing any, as the page constantly refreshes navdata to check distances, etc.