Why is a 3GB graphics card not good for FSX?

[ArjenVdv 190]

Hi,I still can't decide about buying a new graphics card. I know that the GTX560TI is a great card for FSX. But as we are getting much closer and closer to the new platforms XPlane 10 or MSFlight, or whatever platform PMDG is gonna switch to, a better graphics card might be better for future purposes I think. I think that the newer games are gonna ask alot more from the GPU instead of the CPU. So therefore I'm thinking about buying a 3GB GTX580 (whenever I get the money...). But I've read countless times that 3GB graphics card can be causing problems in FSX, because FSX can't use more than 4GB of (video) memory or something... So what? What problems are 3GB GPU's causing in FSX then? Crashes? Freezes? So would it be a good choice to buy a 3GB GTX580 for FSX?

[alandc10 13]

From my understanding, GPU power is not as important in FSX. Infact i have many friends in the flightsim world using GTX260-285 cards and getting awesome visual performance. Personally i use a GTX460 and run 2 24" monitors in FS9 with just about every addon thinkable and get brilliant FPS. 560ti or 580 and you will not be dissapointed.As for the whole "flight" story, its been talked about for ages and people are getting far to much hung up on it. Enjoy what we have now and when flight comes along (wenever that may be) im sure top end cards will be surpassed by something else.Alan

[ArjenVdv 190]

From my understanding, GPU power is not as important in FSX. Infact i have many friends in the flightsim world using GTX260-285 cards and getting awesome visual performance. Personally i use a GTX460 and run 2 24" monitors in FS9 with just about every addon thinkable and get brilliant FPS. 560ti or 580 and you will not be dissapointed.As for the whole "flight" story, its been talked about for ages and people are getting far to much hung up on it. Enjoy what we have now and when flight comes along (wenever that may be) im sure top end cards will be surpassed by something else.Alan

Thanks for your answer, but that was not my question.... :)

[stevenp 1]

I've never heard of that one. Probably won't make a difference. The memory shouldn't make a difference. I'm too lazy too look around so do you have a linky? However, we can get technical into the bit-lines of the controllers and how the fets are hooked up to the memory lines and the memory controller.

[fakeflyer737 991]

uhhhh its simple for FSX. The more VRAM you got the more AA you can use.

[tf51d 284]

You're all forgetting that FSX is a 32bit Application. Even running on a 64bit O/S it is limited to 4GB Virtual Address Space (VAS). Within that space includes the available video memory. a 3GB card would limit the app itself to 1GB. I think you can forget about the NGX running in that environment. A card like this will only benefit 64bit APPS.

[fakeflyer737 991]

You're all forgetting that FSX is a 32bit Application. Even running on a 64bit O/S it is limited to 4GB Virtual Address Space (VAS). Within that space includes the available video memory. a 3GB card would limit the app itself to 1GB. I think you can forget about the NGX running in that environment. A card like this will only benefit 64bit APPS.

uhh no, you are talking Computer Ram, not Video Ram...completely different. I use a GTX 480 w/1.5g and FSX uses ALL of aout 1.4g when in high AG areas with High AA.

[tf51d 284]

uhh no, you are talking Computer Ram, not Video Ram...completely different. I use a GTX 480 w/1.5g and FSX uses ALL of aout 1.4g when in high AG areas with High AA.

No I'm talking about Virtual address space, here's a good explanation of this from Microsofthttp://support.microsoft.com/kb/940105In your case you are ok, because your 1.5gb memory (addressed) +1.4GB applicication = 2.9GB, well below the 4GB limit for a 32 bit Application. If your card was a 3GB card, you would have OOM'd because your VAS would have exceeded the 4GB limit. (4.4GB)Here's another good explanation from Ryan (TABS), which is right on point.

Bert,How do the CTDs you're seeing happen? If they're completely random and happen out of nowhere they're almost surely the result of resource starvation in FSX (contiguous virtual address space) and not something we can really "fix". What are your system specs and what scenery addons are you running at the time when this happens?The basic background is that FSX is a 32-bit application and there's absolutely no way around the hard 4GB VAS limit. If it tries to allocate more than that or if it tries to allocate a large contiguous chunk and can't find unfragmented space for it, the sim is gonna CTD every time. It's the "physics" so to say of how applications work in Windows and DX9. Your video memory amount counts against the 4GB limit too because in order for FSX to address it, it has to be copied/shadowed into the application's VAS. We've had cases at support where people install 3GB video cards and the sim won't even run because it's sitting there with 1GB or less of addressable space after the video memory, which isn't enough to even load the sim and plane.If your crashes are a repeatable thing that's caused by doing something in the FMC or if it's the type of thing where the panel freezes but the sim keeps running, then it'll likely be solved in SP1(Post 48).http://forum.avsim.n...od/page__st__25

[RedSpinnaker 35]

You're all forgetting that FSX is a 32bit Application. Even running on a 64bit O/S it is limited to 4GB Virtual Address Space (VAS). Within that space includes the available video memory. a 3GB card would limit the app itself to 1GB. I think you can forget about the NGX running in that environment. A card like this will only benefit 64bit APPS.

I must be doing something wrong then. I swapped out my dual 580's due to some serious SLI issues I was experiencing. Put an EVGA GTX 580 3GB Classified (http://www.evga.com/products/pdf/03G-P3-1593.pdf) in my machine and have not had any memory issues whatsoever with the NGX. While the card is obviously overkill for FSX, I use the machine for other things as well.

[MrKen 3]

Having 3gb video ram doesn't guarantee oom's, it just makes them more likely. You can also limit fsx's access to video ram. VideoMemoryOverride=x, where x= the amount you're willing to let fsx play with (1-1.5gb) in bytes.

[member111333 8]

Having 3gb video ram doesn't guarantee oom's, it just makes them more likely. You can also limit fsx's access to video ram. VideoMemoryOverride=x, where x= the amount you're willing to let fsx play with (1-1.5gb) in bytes.

That is very interesting. Could you please be a little bit more specific on how to do that exactly.

[MrKen 3]

Here you go...

Guys, here's some points of clarification:1. As stated, FSX is a 32-bit app. It has 4GB of VAS to work with, that's it. It's a hard mathematical limit that arises from taking the number of possible states for a bit (1 or 0 - two) and raising it to the 32nd power, which is 4GB.2. The difference between 32-bit and 64-bit OSes with respect to FSX is that the system resources (video, mobo, sound etc) don't eat into the available physical RAM shown and FSX gets its own 4GB piece of VAS without having to share it with the OS. In 32-bit the entire machine, OS and all, is limited to 4GB.3. There actually IS a way to limit video RAM use in FSX - ******* Altuve (praise his name haha) clued me into this:VideoMemoryOverride=(bytes)The setting needs to go in the part of FSX.cfg that actually references your video card and sets the options its capable of:So on mine this would be[DISPLAY.Device.NVIDIA GeForce GTX 570.0]Mode=1920x1200x32Anisotropic=1VideoMemoryOverride=1073741824That should theoretically limit my card to 1GB of video memory. I have not been able to try this yet, and I have no idea how this setting works with multi-GPU systems. Some of the freeze/OOM reports we've had involve that kind of thing - two 2GB GPUs in Crossfire or SLI. It doesn't seem like knocking each card's entries down to 512MB is the greatest idea... so this may only work with single GPU systems.

[ArjenVdv 190]

I have an idea. I'm gonna get the Asus GTX560ti 1GB. That card should be performing great in FSX. When PMDG switches to a new platform in about 6 months I estimate (most likely XPlane 10), I'm gonna buy another GTX560ti 1GB and put them in SLI. Because XPlane 10 is gonna be a 64 bit application. But if I want to put them in SLI, can I buy two seperate GTX560ti's and connect them using an SLI bridge, or do I have to buy a specific SLI set for that card or something? You know, one package with 2 GTX560ti's?Thanks.

[MrKen 3]

Doesn't have to be a matched set, but you will need to get an sli bridge if you didn't save the one that came with your mb

[dazz 69]

Having 3gb video ram doesn't guarantee oom's, it just makes them more likely. You can also limit fsx's access to video ram. VideoMemoryOverride=x, where x= the amount you're willing to let fsx play with (1-1.5gb) in bytes.

I wonder how does that work. Most of the VRAM usage comes from AA / resolution, which is 100% post processing. I would think FSX has absolutely no control over that....and I don't think there's a problem with running a 3GB GPU in FSX. Most AA modes don't ever use more than 1GB of VRAM. If they use more, your FPS will be in the single digits anyway