How to take some RAM and use it towards Dedicated video memory for the Nvidia graphics card

This is normal for mobile GPUs. At one point nVidia made a system where card would be able to use both its own RAM and system RAM. After that they presented some graphics cards with 32 MiB and 64 MiB of RAM. They could use system RAM, so their total amount of RAM would be 128 MiB and 256 MiB, if I remember correctly. Basically, the dedicated video memory is the card's RAM and the shared memory is the main RAM that the card can use when it needs extra memory. That system remained in their mobile graphics cards. As far as I know, there is no way to check if the card is using that memory or not. I myself have a GeForce 9500M GS on a 4 GiB system and have never had problems with card eating any of my system RAM. On my computer, the shared RAM is 1790 MiB, so it could be that driver automatically sets a certain percentage of system RAM as shared.

EDIT: After doing some calculations, it seems that the shared memory is set to around 43.7% of main system RAM.

Here is article about that technology on NVIDIA's site. Here's another interesting article on the technology.

From what I've read, you won't have any problems with TurboCache using up needed RAM because it only uses RAM not used by other applications and it only uses RAM when it needs to to so and when it will improve performance.

There will be a (hopefully) minor penalty to memory bandwidth on the processor due to the graphics chip in your processor sharing the memory bus with your processor.

As an absolute minimum your on-chip graphics will have a framebuffer that it has to constantly "copy" out to your monitor for it to display. Assuming a 1920 * 1080 display running at 60Hz that framebuffer will need an amount of bandwidth.

That bandwidth will be in the ballpark of 325MB/s (1920 * 1080 * 3 (24bit) * 60Hz).

On top of that you use extra bandwidth for

• video decoding, bandwidth factors include
  1. video resolution
  2. scaling
  3. post processing effects (film grain etc)
• desktop compositing
• anything else the graphics might be doing

When watching video I'd go for a "finger in the air" estimate of about 1GB/s total memory bandwidth used.

Which isn't too bad on a modern system. If you have a modern DDR4 system running in single channel then your memory bandwidth is probably in the ballpark of 16GB/s, in dual channel that gets you 32GB/s.

That's still 1/16th (or 1/32th) of your memory bandwidth though.

With the display to the onboard graphics disconnected I would expect the graphics core to go into a "sleep" mode where it will use next to no bandwidth at all. It will probably have an interrupt set up to monitor the display detect lines.

If you're not doing anything intensive or demanding you probably won't notice the difference. It will have a small penalty in the amount of time taken to copy stuff to your dedicated graphics, but again, probably not noticeable.