sometimes 1 or 2 FPS that's normal considering everything that's going on in the background, but then (sometimes) an 8 - 10 FPS drop depending on the airport.
Ok, the "depending on the airport" part might be important.
Frame rate losses are not linear. Usually, the are very small as long you have plenty of VRAM available, but if you start to get closer to the limit (bigger airports, but also small unoptimized ones), they drop very sharply, because if the sim must start to swap texture memory in and out from/to the system to the VRAM on the card, it's a completely different kind of load.
As usual, the overall load on the sim is NEVER caused by any single addon but, the problem is, it's so easy to disable GSX ( just quit the Couatl engine from the traybar icon ) that, it's also very easy to assume it was the "cause" of the fps loss, because it's not as if you could easily unload the airport or the airplane.
Some example, let's assume GSX requires 5% of the overall VRAM here, it's just an example, I'm not using actual numbers, because they change depending on which vehicles, how many of them (variable number of doors, variable number of luggage carts depending on payload, etc.). Just for simplicity sake, let's assume it's all identical and only the airport change, so GSX in that case would add 5% to your VRAM consumption.
- Some Airport + Some Airplane = 90% of your VRAM taken. Fps is fine.
- Same Airport + Same airplane + start GSX = 95% of your VRAM take, Fps is still fine, maybe a slight 1-2 fps drop on the heavier services like Boarding cargo+pax.
- Different (heavier/less optimized) airport + Same airplane = 98% of your VRAM taken. Fps might still be fine, because you are now just barely under the limit.
- Same (heavier/less optimized) airport + Same airplane + GSX = 103% of your VRAM taken. Now the sim must start swapping memory in/out, and this will cause a significant fps drop.
Can you stop the airport ? Can you stop the airplane ? Can you unload the rest of the scenery around you ? Not really. But you can stop GSX easily, so you can easily say "it was GSX, because I stopped it and the fps went up", even if your VRAM was already almost entirely consumed by the other stuff.
That is the VRAM issue, you can check if this is your issue by looking at the DevMode fps counter and see how much VRAM you have before/after calling GSX
If you have plenty of VRAM instead, we might need to look into the number of objects instead.
