Thanks everyone for the contributions.

 

Note I was not surprised to find the son of FSX choke on Manhattan X with every slider at max. What did surprise was that the Prepar3D memory management choked when everything was thrown at it on a 64bit system. Having run in 64bit since XP x64 I was surprised to see in 2012 an app actually choke for a lack of memory; then again FSX/Prepar3D are not very modern at heart. Frankly though was also pleased as I was looking for limits and I found one.

 

The spec is an Asus overclocked GTX580P GPU with just 1.5Gb of GDDR.

 

Are you aware that video memory decreases the maximum available memory in a 32-bit environment? Thus your 1.5Gb video memory may be a hindrance.

Hi WarpD

 

No I wasn't. Interesting.

 

However, as my PC is a general purpose tool for other games and interests, like home video editing where I use the CUDA engine for the Adobe apps I guess I have to make a few compromises.Which in this case seems to be unsupportive of my Prepar3D flight siming.

Are you aware that video memory decreases the maximum available memory in a 32-bit environment? Thus your 1.5Gb video memory may be a hindrance.

 

Prepar3D is using its own up to 4GB virtual adress space which is allocated in total memory area avaliable for OS. Video memory buffer is allocated in OS adress space, not in Prepar3D adress space. As long as Ost's computer has installed Win7/64 bits and 8 GB of RAM, video memory buffer with maximum size of 1.5 GB can't be significant problem.

Video memory must be 'duplicated' in the application's space with DirectX9.0c

Video memory must be 'duplicated' in the application's space with DirectX9.0c

 

Are you sure that full linear address space of graphics card is duplicated in virtual address space of 32bits process while using DirectX9.0c? What in case of cards with 2GB of video memory working under control of 32bits OS? In this case virtual adress space avaliable for each process is equal to video memory size. What about space for the process itself?

 

I know D3D enviroment slightly, but I was thinking that under D3D communication between application memory and video memory placed on graphics card is done by using buffering technique managed by D3D via WDDM (Vista and Win7), so what is the reason for duplicating whole memory of graphics card in application memory? Can you point me where I may read about that?

 

For any application, without LARGE_ADDRESS_AWARE flag set, working on system with modern graphics card equipped with 1GB or more RAM it could be reason to easily get OoM error.

Video memory must be 'duplicated' in the application's space with DirectX9.0c

 

That is easy to check isn't true that whole video memory range must be duplicated in the application's space. Only you need is FSX running with simple scenery and low settings, graphics card with 1GB or more video memory and Sysinternals Process Explorer to check size of FSX's allocated space (Virtual Size).

 

FSX (low settings and simple scenery) run on GTS450 with 1GB video memory is reporting total used virtual address space below 0,9GB. According to your claims total used virtual adress space should be significantly bigger than 1GB as a sum of memory allocated for FSX program, data and 'duplicated' 1GB of video memory.

 

Applications that use graphics APIs that are earlier than DirectX10 and that target GPUs that have large amounts of video memory can easily exhaust their virtual address space, but isn't true that size of allocated virtual address space for graphics resources must be equal of installed video memory of graphics card. It may be smaller or even bigger due to duplication by WDDM video memory manager virtualized range in addition to the application’s copy of used resources while working under DirectX 9. In such case data is stored in application's virtual adress space twice. With your idea of "duplication' allocated space according to video memory size of graphics card it would have tragic consequences for applications without LARGE_ADDRESS_AWARE flag set, beeing able to use only 2GB of virtual address space.