To begin with, here are my PC specs:Intel core i7 950 @ 4ghz6gb DDR3 1600ATI Radeon HD 5850As you can see it's a fairly stout system. However I have noticed that, for some reason, clouds in FSX absolutely cripple my system if it's more than partial cloud cover. My PC is capable of running very detailed sceneries and aircraft and a locked 30fps constant without sweat (outside of major airports with heavy traffic, as we all know). However as soon as any overcast conditions or stormy weather are present, they will bring my framerate down into the 10-15fps range in a snap. Having high or medium 2.x water (which reflects the clouds in the surface of the water) makes it even worse. I HAVE to set low 2.x water to even fly in overcast conditions and even then it's still choppy.Now I'm pretty sure I've read here before that the ATI cards have some kind of problem with how FSX renders clouds and they have a much larger impact on framerate than they would on a comparable Nvidia card (for example, a GTX 470 which is very similar otherwise in performance to my 5850) but I can't find anything about that now. Is this the case? I am thinking about selling my 5850 so I can switch back to Nvidia, primarly because I miss Nvidia's control panel ability to have unique settings for each game automatically, but also because of this problem with FSX.Previous I had an Nvidia 8800GT on a Core 2 Duo e6750 system and I'm almost positive the clouds did not have this kind of effect on the framerate, even though the 8800 is quite aged by now.

What is your 'cloud draw distance' set to? That makes a big difference on frames. Do you have REX? Not sure about the ATI issue.

I have it set typically to 80mi, but I have tried the lowest settings of 60mi which very slightly improves frames, but only by 2 or 3. It's still killing my system at that setting.Yes I do use REX, but I only use the 1024x1024 clouds, not the "HD" 4096x4096 or 2048x2048 ones.

Yes I do use REX, but I only use the 1024x1024 clouds, not the "HD" 4096x4096 or 2048x2048 ones.

There's the problem, drop the cloud texture size down to 512x512 or 256x256 res.

There's the problem, drop the cloud texture size down to 512x512 or 256x256 res.

Nah, that is not the problem, I have just tried 512x512 and even the 4096x4096. There was little to no difference in framerate for me. I think as long as you have enough video memory, the resolution doesn't make much difference.After searching here some more in the video card/drivers forum, it seems common knowledge that ATI (AMD..) cards do not handle clouds properly as I thought. I'll have to find a buyer for this one. $200 shipped anyone? :D

The money saving option is OC the card to as close to 900MHz as possible (FSX favors NV cards due to the Shader Clock being 2x faster than the Core Clock, thus try OCing the ATI card before jumping ship.)

If I remember correctly, the *******' shader mod 3.0 will help with clouds + ATI

Run, don't walk, and get Bojote's Shader mod. It makes a world of difference on cloud performance on ATI. I use an ATI 4870 HD and the difference in performance of clouds is huge.

To begin with, here are my PC specs:Intel core i7 950 @ 4ghz6gb DDR3 1600ATI Radeon HD 5850As you can see it's a fairly stout system. However I have noticed that, for some reason, clouds in FSX absolutely cripple my system if it's more than partial cloud cover. My PC is capable of running very detailed sceneries and aircraft and a locked 30fps constant without sweat (outside of major airports with heavy traffic, as we all know). However as soon as any overcast conditions or stormy weather are present, they will bring my framerate down into the 10-15fps range in a snap. Having high or medium 2.x water (which reflects the clouds in the surface of the water) makes it even worse. I HAVE to set low 2.x water to even fly in overcast conditions and even then it's still choppy.Now I'm pretty sure I've read here before that the ATI cards have some kind of problem with how FSX renders clouds and they have a much larger impact on framerate than they would on a comparable Nvidia card (for example, a GTX 470 which is very similar otherwise in performance to my 5850) but I can't find anything about that now. Is this the case? I am thinking about selling my 5850 so I can switch back to Nvidia, primarly because I miss Nvidia's control panel ability to have unique settings for each game automatically, but also because of this problem with FSX.Previous I had an Nvidia 8800GT on a Core 2 Duo e6750 system and I'm almost positive the clouds did not have this kind of effect on the framerate, even though the 8800 is quite aged by now.

As a former owner of the 5870, and now the gtx480 I can tell you there is a big difference between the two cards. The gtx480 eats Rex 2.0 for breakfast. I don't know about the shaded mod but weather is not an issue with the newest cards and nvidia. I can report no more stutters, only fluid fps. I have flown in cyclones, hurricanes, thunderstorms and no problems. This is with complex addons in dense scenery over busy airports. This includes FTX orbx Australia!Get the 480 gtx! I say this because I had a helluva time getting the 5870 to work as advertised. I don't mind tweaks but the card should be able to handle the latest stuff without tweaking.

As a former owner of the 5870, and now the gtx480

Which GTX480 have you got as your profile is not updated.Looking at getting one myself.thanks

You know, I don't see how it is helpful that every time someone starts a thread on ATI video cards, a certain group of Nvidia users hijack the thread with claims of superiority for their cards. There are many reasons a person may choose to use an ATI card, some related to FS and some that have nothing to do with FS. It is well known that ATI cards have often had trouble with clouds in Flight Simulator. There is now an excellent fix for this problem in the form of Bojote's Shader mod. With the shader mod applied, the ATI cloud problem simply goes away. Is it unreasonable to expect that we can help ATI users without blasting them for their choice of cards, and trying to sell them Nvidia's latest model?

You know, I don't see how it is helpful that every time someone starts a thread on ATI video cards, a certain group of Nvidia users hijack the thread with claims of superiority for their cards. There are many reasons a person may choose to use an ATI card, some related to FS and some that have nothing to do with FS. It is well known that ATI cards have often had trouble with clouds in Flight Simulator. There is now an excellent fix for this problem in the form of Bojote's Shader mod. With the shader mod applied, the ATI cloud problem simply goes away. Is it unreasonable to expect that we can help ATI users without blasting them for their choice of cards, and trying to sell them Nvidia's latest model?

Couldn't agree much more. You can find a lot of posts of people recomending others spending huge amounts of money in new components, that might be what they're looking for, why not, but not even considering their needs, flying style, if they use other games, or if they simply don't want to spend tons of money on things they don't really need because there's a fix that takes little time and effort or simply because it won't improve what they already have all that much

Which GTX480 have you got as your profile is not updated.Looking at getting one myself.thanks

It's the evga gtx480. I'm rarely at home when I read the forums so when I get a moment I'll update my profile.Not trying to hijack. I just noted that flying through weather is much more pleasurable!

Well... Here are my 2 cents...I'm an ATI 5870 Xfire owner and I most say that when you are flying in a heavy cloud environment, GTX or not GTX you'll see a drop in frames...As for my personal experience... I'm very happy with the results I'm getting from the 5870... of course... after installing Bojote's shader mod...Before the 5870 I had a GTX280 and it was the same thing... a little drop in frames when flying in heavy clouds...Maybe you're having a driver problem or your pc is using a lot of resources in other apps...But... if you want to bail out from ATI.... wait few months until the new graphics card line form ati/nvidia are out...