does running dual monitors hurt video performance?

[slightlyhuman]

i have a 19'' crt and 14'' LCD running dual monitor on a 9500 np@ 9700 pro

I play games and such on the 19''. Running dual monitors, will it hurt my fps or lag my gameplay while having a 2nd screen going even if its just sitting there at the desktop while playing games?

 

[BlueWeasel]

I would think running dual monitors would certainly hinder performance when playing games. Additional bandwidth of the card is required for the second monitor and can't be used by the game. Whereas, running a single desktop allows the game to have as much resources as possible.

However, with today's high-end video cards, the extra bandwidth required for the second desktop is pratically negligible. I have no idea now that translates into game performance.

Have you tried running the games in dual mode yet? When I was running 2 displays, most of my games didn't work very well with the second desktop enabled, so I just kept switching back and forth between single and dual modes.

 

[Viper96720]

Doesn't most cards have dual ramdacs. Although if I start a game the second monitor blanks out.

 

[ponyo]

I don't think dual monitors hurt video performance. If it does then it's minimal. I don't notice any loss in performance with my dual setup.

 

[VIAN]

2D:

In select cards, not included in current generation cards less than 100 dollars, Dual RAMDACs are provided for optimal performance using a dual setup. No performance is lost.

3D:

Is that possible?

 

[BDawg]

Originally posted by: VIAN
2D:

In select cards, not included in current generation cards less than 100 dollars, Dual RAMDACs are provided for optimal performance using a dual setup. No performance is lost.

3D:

Is that possible?

Yes, it's possible with the Parahelia.

 

[Peter]

The RAMDAC is just doing color space conversion for analog monitors. This is nothing, absolutely nothing to do with performance.

Each monitor eats into the card's RAM bandwidth, simply because the output pipe has to read the frame buffer many times per second to feed the picture out to the monitor. E.g. at 1600x1200 85 Hz true color, that's 680 MB/s. This is noticeable.

 

[VIAN]

Well, the quicker the RAMDAC, the more response you get, right.

Also heard a lot of reviews that a RAMDACs speed tells max res and refresh of the card. Is this true?

 

[VIAN]

...hi again.

 

[Peter]

Originally posted by: VIAN
Well, the quicker the RAMDAC, the more response you get, right.

Also heard a lot of reviews that a RAMDACs speed tells max res and refresh of the card. Is this true?

The RAMDAC has no speed. It is a Digital to Analog Converter that is fed pixels and puts out RGB. There is a maximum useful pixel frequency above which the output signal quality gets too fuzzy. This is the "XXX MHz RAMDAC" value you see.

In contrast to your theory, actually, the higher you crank the refresh rate (and thus the frequency the RAMDAC is being used at), the more bandwidth does the pixel feed require, and the slower does your rendering get.