This is totally a newbie question, but if I'm running two 17"widescreen (1440x900?) monitors; extended, not cloned, how much memory is required on a graphics card to run them without using system memory? Am I correct in thinking that the application only determines the required speed, gaming or video=fast,smart GPU and workstation apps= slow, not so smart GPU, but the memory required is determined by the maximum resolution/bit depth?

About 5mb video ram for each display at most.
 
((1440*900)*32)/8 is the math, if you were wondering.

Thanks asds,

so if doing word processing, a graphics card with zero memory and a graphics card with 512M both rely on system memory to drive the monitors? the 512M only gets used for shading/rendering such as in gaming?

It will only rely on system memory if it is an Integrated graphics card.
 
I have personally never seen one with two monitor outputs, so I guess you don't have that.
 
Other graphics cards always use the built in ram to display 2D and 3D.
 
With any given game in 3D, dual screen will land on a minimum of 256mb video ram.
 
In 2D nearly no video ram is required compared to what 3D needs.
 
You do not need more system ram to display two images, unless you use 3D studio or something in that weight class.

thanks to you both.  
 
I will take 10 megs as a good estimate of the memory needed on a (non-integrated) graphics card to drive two 17" widescreen monitors in 2D apps.
 
3D/gaming/video etc will place higher memory demands on the graphics card.

Actually there is a Matrox DualHead2Go device that allows you to game over multiple monitors.

Yep, I think you got it right.
And really with any graphic card with two outputs this simply won't be an issue.
 
bfellow is a little misinformed, it will work on any nvidia graphic cards in games, and with ATi as well as far as I know.
 
I have the 4096x1536 screenshots to prove it works on a 7900GT

Actually there is a Matrox DualHead2Go device that allows you to game over multiple monitors.

 
W O W 8O

This is completely off topic, but I figured I should upload it anyway
 
Pretty sweet, but at 328mb vram usage, and 5fps you can see why this wasn't particularly playable
 
 

well I didn't say it didn't work on Nvidia cards!  I just said Matrox has some cards too!

I think veryone is stepping over each others feet.
 
The OP already has his basic answer but yes it depends on resolution, colour depth and also what the chip is doing (fairly static 2D is basic res x colour depth. But of course add complexity layers, textures, etc and whether it's 2D or 3D things start to add up. You ould technically display on 1MB per monitor, but the bit depth would need to be thousands of colour or 16bit low res.
 
MP is talking about 3D gaming which uses RAM for a ton of things not just screen buffer to write out to TMDS/RAMDACs.
 
And Bfellow, while the Matrox Dual/TripleHead2GOs are sweet and provide multimonitor support for dual and triple monitor setups, it still needs to be sent that full res image from the graphics card which means the graphics card itself needs the memory to be able to display the image at those settings.
 
Hope that helps clear things up.