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Discussion in 'MacBook Pro' started by iamrawr, Apr 22, 2010.
Is it possible to allocate system ram to it? Out of curiosity.
It's not hardwired to.
Because Apple has, as always, limited it. If it was a PC, then I think you would be possible but as it's a Mac, it isn't. It's a "feature" in the driver and there is no nVidia tool for OS X anyway.
It's pretty useless anyway as the VRAM don't really speed up anything, maybe few FPS in games, that's all but it's better to leave the RAM for system, not for GPU
Only integrated GPUs actually use system RAM directly. Discrete GPUs use VRAM because it is faster than system memory. It can still use system memory to store textures when VRAM is full and ask the driver in the OS to fetch them, but it is slower than storing it in the GDDR3 memory.
This is automatic, and built into OpenGL and DirectX.
so are you saying it kinda does in a way?
i don't know very much about GPU's and VRAM.
thanks for all the replies so far =D much appreciated
The system already does the only thing it could do for "allocating" regular system memory to the GPU.
Think of it like how the OS uses RAM.
When RAM gets full, it starts moving some of the data to the hard drive to make more room, and will swap data between the hard drive and RAM as needed. It tries to keep data in RAM because it is much faster than your hard drive.
VRAM acts much in the same way. It stores textures (for games, apps, whatever) and when it gets full, the driver starts storing the excess in RAM, and will swap textures back and forth between RAM and VRAM. And again, it tries to keep as much in VRAM as possible, as it is faster then RAM for the GPU to access.
Okay so then it's useless to buy the 512mb model then?
No, as the GPU has more space and will swap if necessary at a later time.
Exactly, but in practice, it really only benefits games that use a large number of textures, or large textures.
So i'm guessing there is a certain limit that it will swap with the regular RAM correct?
Yeah, when it runs out of RAM. Say I have a game that pushes some textures out to the card, any that don't fit will remain in the game's RAM space. Even ones that do fit will be in the game's RAM space as well.
In reality, not many situations will push much more than 512MB worth of textures onto the card. And in those cases, the GPU itself might be the bottleneck to handling more.
VRAM used to be a big deal, but that was in the age of 16-32MB of VRAM. Around the time 32-64MB VRAM became the norm, then companies like nVidia and ATI offered up this solution. These days, VRAM is best referred to as a cache for the rendered frame and the textures/data it needs.