What happens if...

[storm5510]

A straightforward question: My GPU has 8GB of VRAM. What happens if a GPU application attempts to exceed the capacity? Does said application (a) freeze the system, or (b) reach into the main system RAM to get what it needs, or (c) produce another negative result?

[kriesel]

Depends on the application and other details. Failure to allocate the requested gpu ram with a fatal error resulting is a common occurrence. Spilling to system ram or even paging file may occur, with a severe reduction in memory bandwidth and throughput (PCIe traffic is much slower than gpu ram) giving the appearance of a hung gpu application. If the app fails to detect that memory requested was not allocated, and proceeds anyway, garbage output seems likely.

Also depends on OS and how well and how much it virtualizes the gpu, whether it's been tweaked, etc.
https://appuals.com/how-to-increase-...on-windows-10/
https://en.wikipedia.org/wiki/Memory_virtualization
https://www.techwalla.com/articles/h...graphic-memory

Going in the other direction, using excess gpu ram for a ram drive: https://www.softpedia.com/get/System...am-Drive.shtml

[storm5510]

Originally Posted by kriesel

Depends on the application and other details. Failure to allocate the requested gpu ram with a fatal error resulting is a common occurrence. Spilling to system ram or even paging file may occur, with a severe reduction in memory bandwidth and throughput (PCIe traffic is much slower than gpu ram) giving the appearance of a hung gpu application. If the app fails to detect that memory requested was not allocated, and proceeds anyway, garbage output seems likely.

Thank you for the reply. I suspected as much. There would be an allocation error. A program like gpuOwl would produce incorrect results, if it would run at all. I only asked because I had not seen anyone else here inquire about it.