What purpose does the video memory serve on video cards?

[ibex333]

What advantages does a 640mb video card have over the 256mb card is the core/clock speeds are the same?

Why is there 256mb cards that are faster than 512mb cards? How can this be? I thought that memory makes your card faster, no?

Finally I heared that all the extra memory really does is it allows you to play at a higher resolution...


The reason why I'm asking is because there's a g80 with reduced memory coming soon that will cost $300. If the only drawback of the reduced mem is that I cant play at high res, that's perfect for me! All I need is speed and DX10 support. No need for very high res with my 17 inch monitor.

 

[Matthias99]

I thought that memory makes your card faster, no?

Uh, no. At least no more than "RAM makes your CPU faster".

The memory on the video card is used to store all the stuff that is being drawn on the screen when you are running 3D applications. The video card has to have enough memory to hold all the polygon and texture data that is being used to draw the current scene. Some memory is also used for running shader programs in DX8/DX9 games that use pixel/vertex shaders. So if you want to run your game with higher detail settings, and/or with higher-resolution textures, it will use more VRAM.

IQ-improving techniques such as AA and AF also use extra video RAM -- AA in particular, since the video card has to draw the scene internally (at least partially) at a higher resolution and sample it down. So the higher the AA/AF levels, and the higher the resolution of the output, the more memory these will take up.

Higher resolution by itself does require some extra memory (for the larger double/triple frame buffers), but it's not usually that much. A 2560x1600x32bpp framebuffer is only ~16MB.

If the program you are running is only using, say, 100MB of memory on the video card, cards with the same GPU/RAM clocks but 128MB/256MB/512MB of memory will all run that program at the same speed. If the program needs, say, 200MB of VRAM, the 128MB card would run it a lot slower. Most games today are written to 'fit' on a 128MB/256MB card, sometimes with an option to use super-high-resolution textures or extra-detailed models if you have 512MB of VRAM available.

 

[TheRyuu]

It uses the RAM to store texture and other graphics related information to keep it nice and "close" to the GPU.
With it "close" to the GPU you can have the higher transfer rates (50+ GB/s) instead of the 4GB/s that you get with PCIe.

Also, in general, higher resolutions use more vram.
And I'll add an example:
When I played Dark Messiah (DMOMM) on my old 7900GT's @GTX speeds @1680x1050, I could not run it at max settings. Now, my new card is about as fast as my older SLI cards but it has loads more vram.

I can now play DMOMM at the same resolution only on max settings.
Now the 8800GTS does have slightly better performance in shader heavy games (like the source based game DMOMM) but I really think it's the vram that helped my performance almost ten fold.

 

[ibex333]

So.... If I dont plan on running games any higher than 1280x1024, a 320mb G80 could be enough, right?
Do you think there's any game out there right now that I wouldnt be able to run with max settings at the above specified resolution?

 

[morgash]

Plus there is the fact that alot of companies exploit people by making cards with more RAM, but they use sh*tty RAM that is much slower to cut costs. That is why you end up with 256mb cards being faster than 512mb cards. It's all a marketing thing because they know that someone who knows nothing about it is gonna look at that and say WOW! thats two times more for only a little more in price. That's got to be better. The general rule is this:

Slow, old GPU - more RAM is not really going to make a difference. The card is too slow to take advantage of it. So all the extra RAM is doing is holding the stuff there, waiting on the GPU to process it, you arn't going to see any advantages and with most low end cards they will actually end up being slower the more RAM they have.
Fast, new GPU - more RAM will make a big difference in the amount of AA and AF and the res you can run the game at because the card is so fast it can actually use all the textures 512mb or 640mb of RAM can hold.

Now since you are running at 1280x1024 the 320mb 8800gts would be a perfect card for you. With it you could run everything at 16xAA full AF, hell full everything and be fine. So grab it when it comes out and have fun

morgash

 

[morgash]

as an example:

THIS card would be much faster than THIS card despite having half the amount of total RAM. The first one uses much faster GDDR3 while the second uses slower and inefficient GDDR2 to cut costs.

morgash