I own a Dell XPS 400. It's not the best gaming system (and it's a Dell...), but it has served me well for the 8 or so months that I have owned it. I can have all my FSX settings on "High" without much of a problem.There was one thing, however. As many of you have probably experienced, having the default FSX traffic setting on "High" will give you about one out-of-place Pacifica 737 and two Baron 58's. So, naturally, I ed it all the way up to 100%. There still wasn't a realistic amount of air traffic, but nevertheless, any large amount would cut my frame rate in half. Still unsatisfied with the default traffic, I purchased Ultimate Traffic 2007. I did so after reading several reviews, which affirmed the fact that the program was very good with giving you plenty of traffic and keeping your frame rate normal. (You can probably see where this is going.)To make a long story short, without traffic and with clear skies I get my usual 24 fpm (the default setting I locked.) With traffic, I get about 1 frame every 3 seconds. There are other factors involved with the reduced frame rate-- weather gives it a nice punch to the stomach-- but traffic is the main thing which demolishes the visual performance.I should note that I have an Nvidia Geforce 6800, which is uh... somewhat sub-par in terms of a video card for FSX, and my sound card is not exactly top of the line either. I can't give you the exact specifications, but I do know that it is incompatible with a few things on my computer.My question is this-- despite the fact that I have little trouble with the other settings in FSX, why does traffic do so much damage?

This is basic computing 101. For each calculation that the machine makes, performance drops. More calculation, (AI positioning), more performance loss. Pretty simple.

There are several reasons, some of which I'm outlining here:1) add-on traffic models can be very detailed and add many triangles to render per frame, increasing scene complexity very quickly. The performance needed to render the extra information is very costly, and by far the biggest performance hit on a computer.2) add-on traffic increases the amount of additional airlines rendered compared to the default traffic. Most add-ons provide the same traffic in the 20% density as the 100% density in the default traffic.3) the type of aircraft and textures must be loaded in memory, which increase the object types. The more the object types, the slower the overall simulation gets (and one of the reasons some optimizations involve decreasing the type of trees or auto-gen houses for example).4) when loading a flight at a busy airport with moving jetways (animations set to high), all jetways will animate at the same time, one per aircraft. This is a major frame rate killer, and even the fastest computer able to run FSX will choke.Of all the things you can do to slow down rendering (frame rates), adding AI traffic is easily one of the better ways to achieve this.Cheers,Etienne

Yes AI is the #1 frame rate killer in the sim.If you use add-on AI, depending on the package(s) generally 80% is about the highest you would want to use--and this is for a multitude of reasons, some of which have nothing to do with performance, but rather have to do with the ATC system and how much AI it can be expected to reasonably handle.RhettAMD 3700+ (@2585 mhz), eVGA 7800GT 256 (Guru3D 93.71), ASUS A8N-E, PC Power 510 SLI, 2gb Corsair XMS 3-3-3-8 (1T), WD 150 gig 10000rpm Raptor, WD 250gig 7200rpm SATA2, Seagate 120gb 5400 rpm external HD, CoolerMaster Praetorian

I thought 2 aircraft was the max it could safely handle, and even then, AISmooth is needed to prevent you from getting a take-off clearance at the same time the only other plane lands on top of you :)Seriously, the AI ATC seems to handle up to about 80 planes well, although you do get a lot of close calls.Etienne