I haven't noticed any serious cloud performance with my Visiontek 3870 OC @ 840/1200. I do think that a 3850 would have problems. Try using the Simple clouds setting. Something worth trying is deleting the FSX.CFG file and let FSX re-create it.

>I'd just like to know where you got an E8500 - haven't been>able to find any here in the US...>>Sure am glad I got mine when I did then. Nothing like fsx with an e8500 running stable at 4.2Ghz on air. The move from a ATI 1950XT to an Nvidia 8800GTS 512 was also a great move for me...and no significant perf drops from clouds here. Although i AM toying with the idea of grabbing and ATI 4870 now...hmmm...not for FSX per se but my other games would probably see an nice improvement,,,Gino

Same problem here. Overcast clouds will bring my system to a crawl and if flying too close to them will also do the same thing. I can't use ASX at all because of this and here's my spec...E8600 @ 4GHZ-8800GTX-4gigs 1066 RAM-VISTA ULTIMATE 64bit with all updates incl Acceleration. It's not top of the line by today's standard but you'll think it would at least run FSX reasonably well.

Have you tried reducing AA?For me, going to 2X AA made the biggest improvement (almost no FPS hit with clouds). However, image quality takes a hit.