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General Forums => Hardware and Software => Topic started by: Dark on February 09, 2010, 02:01:42 AM

Title: DVI vrs VGA
Post by: Dark on February 09, 2010, 02:01:42 AM
OK just a simple question. Is there any performance gain if I use dvi or vga. Reason I'm asking is I currently run a vga line with dvi adapter. I got a dvi line for free and was thinking of hooking it up. Problem is it would be a chore to do and the line is 25ft long so would have to wrap it up somehow.  Monitor has all the diff conections and so does the gpu so there won't be any adapters at all. Just wondering if it would be worth my time
Title: Re: DVI vrs VGA
Post by: Ghastly on February 09, 2010, 06:05:14 AM
DVI is better than VGA, all else being equal.  However, I've never heard of a 25 ft DVI cable for use with a computer.  Unless it's the highest quality imaginable (i.e. 30+ dollars per foot) I have a hard time believing that it's not going to suffer a serious loss of bandwidth over such a distance.

Ideally, you want video cable's to be as short as possible.  And a short VGA cable might be better visual quality than an overly long DVI cable, depending upon environmental factors.

How's that for a non-answer answer?

<S>

Title: Re: DVI vrs VGA
Post by: TequilaChaser on February 09, 2010, 06:59:28 AM
I agree mostly with Ghastly, however I have always noticed my DVI connection will cut my frame rate gain by 5 or 10 FPS over hooking it up thru VGA connection........
why that is I do not know...... it might just be my monitor....DELL UltraSharp 19" LCD ( has both types of connections )

I use the DVI connection though, WindowsXP gives me 70 framerate.... same PC/Monitor I get 75 framerate in Windows 7....using 1280x1024 res........

hope this helps.......
Title: Re: DVI vrs VGA
Post by: Kermit de frog on February 09, 2010, 07:01:50 AM
If the signal for the DVI cable is in digital mode, you will have a better colors and less pixel jitter, especially for long cable runs like in your situation.
Title: Re: DVI vrs VGA
Post by: Masherbrum on February 09, 2010, 07:08:49 AM
If the signal for the DVI cable is in digital mode, you will have a better colors and less pixel jitter, especially for long cable runs like in your situation.

Correct.
Title: Re: DVI vrs VGA
Post by: SIK1 on February 09, 2010, 10:10:31 AM
You can find your cables here.

http://www.monoprice.com/products/subdepartment.asp?c_id=102&cp_id=10209

They are as good or better than monster cable, and a heck of a lot cheaper.
Title: Re: DVI vrs VGA
Post by: gyrene81 on February 09, 2010, 11:27:15 AM
If the signal for the DVI cable is in digital mode, you will have a better colors and less pixel jitter, especially for long cable runs like in your situation.
Yes and there is a difference between the cables and the connections:

(http://www.avforums.com/forums/attachments/satellite-tv/130487d1248386820-dreambox-similar-dvi_connector_types.gif)


My freebie cable was a DVI-A so I went and found a DVI-I (dual link)...much better picture quality.
Title: Re: DVI vrs VGA
Post by: BaldEagl on February 09, 2010, 02:56:16 PM
I use a DVI cable.  For some reason when I use a VGA cable my 8800 GTS 512 G92 and LG 22" monitor won't scale properly and place the picture in the middle of the screen with black surrounding it unless the source is set at my monitors resolution settings.  With a DVI cable it automatically scales to fit my screen.
Title: Re: DVI vrs VGA
Post by: Dark on February 09, 2010, 11:48:42 PM
Well the cable is a dual link cable with the pics that you posted. Quality is just fine with the vga cable I run now just wondering if it would give any performance increase if I was to switch it to straight dvi. Guess will just stay with the VGA cable. Thx fellas

Dark
Title: Re: DVI vrs VGA
Post by: Kermit de frog on February 10, 2010, 12:36:39 AM
The performance increase will result in improved colors.
Title: Re: DVI vrs VGA
Post by: Masherbrum on February 10, 2010, 01:12:22 AM
The performance increase will result in improved colors.

Yep again, if your Monitor is DVI capable, utilize it. 
Title: Re: DVI vrs VGA
Post by: Tigger29 on February 10, 2010, 10:50:46 PM
Well the cable is a dual link cable with the pics that you posted. Quality is just fine with the vga cable I run now just wondering if it would give any performance increase if I was to switch it to straight dvi. Guess will just stay with the VGA cable. Thx fellas

Dark

Just hook it up and see!  It's just a cable... I know it's way too long but it can't be THAT big of a deal, right?
Title: Re: DVI vrs VGA
Post by: gyrene81 on February 11, 2010, 09:27:53 AM
Just hook it up and see!  It's just a cable... I know it's way too long but it can't be THAT big of a deal, right?
Uh yeah it can...there are limitations to wired connections...and the closer you get to that limit the more likely you're not going to get good results.
Title: Re: DVI vrs VGA
Post by: BaldEagl on February 11, 2010, 12:42:01 PM
Uh yeah it can...there are limitations to wired connections...and the closer you get to that limit the more likely you're not going to get good results.


Uhoh... my DVI cable was too long.   :noid

(http://static.howstuffworks.com/gif/nuclear-test-1.jpg)
Title: Re: DVI vrs VGA
Post by: Masherbrum on February 11, 2010, 01:00:42 PM
Uh yeah it can...there are limitations to wired connections...and the closer you get to that limit the more likely you're not going to get good results.


A digital signal will not be affected. 
Title: Re: DVI vrs VGA
Post by: Skuzzy on February 11, 2010, 01:06:22 PM
A digital signal will not be affected. 

Actually that is not true.  A digital signal is more apt to produce ring-back on the cable making the length of the cable critical.  If the cable length is a harmonic of the switching frequency of the signal, it is very possible to trigger false signals, or to cancel out good signals depending on the switching level of the signal.

Also due to capacitance and resistance it is very possible to get a cable too long, which will degrade the level to a point where it may not be recognized at the other end.
Title: Re: DVI vrs VGA
Post by: Masherbrum on February 11, 2010, 03:02:33 PM
Actually that is not true.  A digital signal is more apt to produce ring-back on the cable making the length of the cable critical.  If the cable length is a harmonic of the switching frequency of the signal, it is very possible to trigger false signals, or to cancel out good signals depending on the switching level of the signal.

Also due to capacitance and resistance it is very possible to get a cable too long, which will degrade the level to a point where it may not be recognized at the other end.

Agree, however the Digital Signal will be "less effected" than an Analog VGA signal.
Title: Re: DVI vrs VGA
Post by: Skuzzy on February 11, 2010, 03:27:41 PM
To some degree.  Analog signals are pretty robust and not subject to some of the issues a digital signal are, but an analog signal is more susceptible to noise/EMI interference than digital signals are.

In a noise/EMI free environment, analog is actually better than digital as far as being robust is concerned.

Take a look at all the analog buses in a computer today (and more on the way).  PCI-E, SATA, USB,...  These are all analog buses carrying digital data.
Title: Re: DVI vrs VGA
Post by: gyrene81 on February 11, 2010, 03:27:52 PM
Agree, however the Digital Signal will be "less effected" than an Analog VGA signal.
That is true depending of course on the source as well as the cable quality. DVI specs as of right now state a maximum length of 10 meters although with the higher performance video cards 40 feet is easy...those specs are based on maintaining signal integrity...if you don't mind some loss here and there, longer distances can be pushed.
Title: Re: DVI vrs VGA
Post by: Ruler2 on February 11, 2010, 04:00:08 PM
http://cgi.ebay.com/25FT-DVI-D-DUAL-LINK-DIGITAL-VIDEO-CABLE-M-M-GOLD-25_W0QQitemZ200433244637QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2eaac099dd <That should float your boat!   Although I don't know if using dual link over single link gives you any performance boost or not, it IS a good deal.
Title: Re: DVI vrs VGA
Post by: Kermit de frog on February 11, 2010, 05:17:54 PM
DVI can eliminate the "Digital to Analog to Digital" conversion process which eliminates noise and data "color" loss.
DVI also has better transmission standards when compared to VGA transmission standards.

Also, I though USB, PCIe and SATA all used digital transmissions using differential signaling and NRZ with 8b/10b encoding.  I did not know it also used analog in the final stage transmissions. 
Title: Re: DVI vrs VGA
Post by: Skuzzy on February 11, 2010, 06:48:15 PM
NRZ is just the data encoding method.  The USB, SATA and PCE-E buses are serial buses carrying digital data.  The very nature of a serial bus has its basis in the analog world.
Title: Re: DVI vrs VGA
Post by: Kermit de frog on February 11, 2010, 07:59:04 PM
My mistake, I was viewing NRZ as a type of signaling, rather than a higher level of encoding.   :o


I've always wondered if the "quad pumped" CPU bus used analog modulation to achieve more bits sent per cycle.  This true?
Title: Re: DVI vrs VGA
Post by: denniswilha on February 11, 2010, 08:09:28 PM
I use the matrox triple head2go system, i tried using DVI single on all three monitors, it would not produce any high resolutions, checking specs with matrox it required DVI dual, so i invested in 4 of them 1 to each monitor and 1 to the pc from matrox unit, made a world of difference, it supports all the higher resolutions. i know they make VGA units but have no idea what resolutin they will support. Dvi in my opinion is by far better in quality, and performance, as far as price VGA is cheapest, you get what you pay for.