Intel GMA950 and system RAM

Question

I'm trying to make sense of the actual RAM used by the video system on my mini. There are some clues at http://docs.info.apple.com/article.html?artnum=303407 - but I want to dig a bit deeper...
At the moment, on my mini - both vm_stat and the Activity Monitor reports 493M of RAM so I'm guessing only 19M is presently in use by the video card?
Does anyone know how to influence this?
What amounts are other people seeing?
With only one sample - it looks to me like the 80M is a conservative over estimate so that people don't get surprised if/when that much actually gets used.

Answer 1

It could be that this shared memory system is different from the typical PC setup.
For example, on my Compaq, I can select how much video memory I want to set aside from my system's main memory for video purposes.
I can choose: 32 MB, 64 MB, or 128 MB.
Since I have 1.5 GB of RAM in the Compaq, I set it to 128 MB.
That memory is constantly pulled-aside. It is never available for the rest of the system. So, as for as the system is concerned, I only have 1408 MB of RAM in my computer.
The other 128 MB is mapped directly to the video system.
I would expect that in Apple's design, they are allowing the memory to be used as needed. That might account for why you have only 19 MB missing now.
That would mean that you have the 16 MB overhead being used, plus the 4 MB of Video Memory.
Apple's design provides 64 MB of video memory plus 16 MB of overhead for the controller. That adds-up to the 80 MB that they publish.
So, as stated above, my best guess, is that your system only needs 4 MB of video memory for what it is doing at the moment. It may draw on more memory as it needs.
This is probably a better solution than always losing the full 80 MB of RAM.
Again, this is just guesswork though.
Hope my thoughts are of some help.