Alt full screen and momentarily higher frame rates

I wonder if any of you have noticed this occurrence or if it is just specific to my computer. If, during my flight and especially on the ground where there is lots of scenery, I hit the alt button, which brings up the menu bar and freezes the action, and then immediately resume the simulation, my frame rates momentarily increase. If I am at Seattle International, for example, and am taxing around and am getting 10-11 frames per second and momentarily hit the alt button and then resume, my frames will, for about 10 to 20 seconds, go up to 14-15 or so. Perhaps by pressing the alt button it dumps scenery from the videocard and then after a while the scenery reloads in a portion (whatever that may be) of the videocard's or main memory thus using a lot of extra resources. The momentary increase in frame rates I get is about equal to that if I use FS2004 in the windowed mode. Anyone else noticed this?Here are some of my current computer specs and settings:ASUS A7V8X (KT400) Award BIOS 1024 (most recent)AMD Athlon XP 3000+ (2240 333mhz)1.024GB (333mhz SDRAM) ATI Radeon ATI 9800 Pro (128mb) Catalyst 3.8 driverWD 80GB (8mb cache) hard driveSoundBlaster Audigy soundcard Thanks,RobbRobb