I asked a question on an other AVSIM (Hardware) forum.

 

Answere: Yes GPU with more Memory can cause OOMs because it fills VAS !!!

 

 

read here:

 

http://forum.avsim.net/topic/425856-gpu-memory-size-and-influence-on-vas/

I have an Nvidia Titan and only get OOM errors when I don't clean up duplicate afcad files, especially with Orbx scenery

I got a response from someone I really thrust when it comes to things like this.

 

quote:

Driver model was changed with Vista SP1/Windows7 and GPU memory is not mapped like it was with XP

 

VAS creeping up as the flight continues is normal. Time + scenery/aircraft is your enemy with FSX

unquote.

You could just run no scenery add-ons and never have a problem? At least, it's never seen me wrong...

Answere: Yes GPU with more Memory can cause OOMs because it fills VAS !!!

I don't believe that is the case. A graphics card is a separate computer with its own processors and memory. there is no reason why FSX should need direct access to all the graphics card memory.

 

This view is supported by bhollis of Lockheed Martin said on the Prepar3D forum "a high end 2 GB card will likely run better than a low end 4GB card". The implication is that a high--end 4GB card would be even better.

 

Prepar3D (like FSX) is a 32-bit application which has a maximum of 4GB VAS on a 64-bit system. If all the graphics card memory counted against VAS then a 4GB would use it all and FSX/Prepar3D couldn't run at all. A 3GB card would leave only 1GB. A 2GB card would leave 2GB VAS which is the unsatisfactory amount FSX had on a 32-bit system.

GPU memory size reduces the VAS available to FSX on 32 bit systems, which have a total of 4GB address space available, but not on 64 bit systems. With those it's only about how much VAS FSX needs.

 

On my system, with a 1GB GPU plus whatever memory Windows needs to run, I only have just over 2GB VAS available for FSX. But the 777 runs OK if I'm careful with FSX settings.

According to its website the AMD HD 7990 graphics card has 6GB of memory. Its system Requirements include

 

Windows Vista®, Windows® 7 or Windows® 8 operating system. 64-bit operating system highly recommended

 

.

That means it can be used on a v32-bit operating system. Its 6GB are significantly greater the maximum 4GB of VAS on 32-bit systems. That shouldn't be possible if all graphics memory counted against VAS.

I re-confirm. On Win7 GPU memory is not mapped in FSX VAS.

 

See post #3.