# Is there such thing as Virtual Video Memory?



## Heart (Jan 16, 2001)

Just like in OS 9 you could use virtual memory to fake out your programs into thinking you had more memory that hard memory.

Can this be achieved on a video card?

I have this 8MB card and I want to play ALIAS but it wants 16MB?

 Please no answers requiring a soldering gun


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## Kosh (May 27, 2002)

No, there is nothing such as Virtual Video Ram. Any such thing would be way too slow. As it is, Video RAM is usually much faster than normal RAM in a Mac.


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## jfpoole (Sep 26, 2002)

Heart wrote:
"Can [virtual memory] be achieved on a video card?"

Generally, no, but there are some video chipsets that use system memory as video memory. Intel produced a number of graphics chipsets that do this, (the latest being the Intel 845GL), and from what I've heard the performance isn't horrible (GeForce 2 MX class, I believe). Other chipset vendors could do this as well, but I'd imagine you'd take a fair hit in performance.

Not that this helps you, though


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## hayesk (Mar 5, 2000)

<BLOCKQUOTE>quote:</font><HR>Originally posted by Kosh:
*No, there is nothing such as Virtual Video Ram. Any such thing would be way too slow. As it is, Video RAM is usually much faster than normal RAM in a Mac.*<HR></BLOCKQUOTE>

Actually, isn't that what one of the main features of AGP? If you run out of VRAM, it uses your regular system RAM, although at a big performance hit.

If a game or app recommends more video RAM, then you probably really need it for it to be useable.


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## Kosh (May 27, 2002)

<BLOCKQUOTE>quote:</font><HR>Originally posted by hayesk:
*
Actually, isn't that what one of the main features of AGP? If you run out of VRAM, it uses your regular system RAM, although at a big performance hit.

If a game or app recommends more video RAM, then you probably really need it for it to be useable.*<HR></BLOCKQUOTE>

I had heard that too. But my guess is it started out that way, but as games progressed, RAM got cheaper, and video cards faster, game programmers started on relying on textures being in the video card's RAM. There's many examples where if you don't have a video card with enough RAM, it will get loaded with enough textures eventually, and the game will crash because there isn't enough video RAM.


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## jfpoole (Sep 26, 2002)

hayesk wrote:
"Actually, isn't that what one of the main features of AGP? If you run out of VRAM, it uses your regular system RAM, although at a big performance hit."

You're right. According to Intel, one of the motivations for AGP was to allow video cards to operate on textures not only in video memory, but in system memory, too. Considering that AGP4X bandwidth is over 1GB/sec, that's not too bad (although the memory bandwidth on a GeForce 4 Ti 4600 is 10.4GB/sec...)

Here I thought AGP was just for moving textures and geometry into video memory as fast as possible, too.


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## gordguide (Jan 13, 2001)

Very few Macs were ever made that required (or could enable) shared memory for video; for the most part nearly all models use dedicated video RAM. It is fairly common on PCs though.


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