Is the MacBook DVI out dual link?

Killyp

macrumors 68040
Original poster
Jun 14, 2006
3,860
5
Is the MacBook's DVI dual or single link?

Many thanks!
 

danhig123

macrumors member
Sep 1, 2006
54
0
What exactly does 'dual link' mean? This is probably really obvious so apologies.

My brothers macbook runs a second display from the DVI port, and you say that this i single link.... but my Mac Pro with the standard video card is Dual Link. It also has 2 DVI ports on instead of one....

So whats the deal and what can I do with my Mac Pro?

Danny
 

Chone

macrumors 65816
Aug 11, 2006
1,223
0
danhig123 said:
What exactly does 'dual link' mean? This is probably really obvious so apologies.

My brothers macbook runs a second display from the DVI port, and you say that this i single link.... but my Mac Pro with the standard video card is Dual Link. It also has 2 DVI ports on instead of one....

So whats the deal and what can I do with my Mac Pro?

Danny
In a nutshell: Dual-Link DVI means a single DVI port that can support a resolution of up to 2560x1600, which only 30" monitors (like the Apple Cinema Display or the Dell 3007FPW) can display.

Your Mac Pro has a 7300GT with a Dual-Link DVI port and Single-Link DVI port for a total of 2 DVI Ports and support for up to a 30" Display on one port and up to a 24" Display on the other port.
 

natethelen

macrumors newbie
Dec 13, 2006
9
2
Connecting to Dual-Link anyway

So I plugged my white macbook to a 30 inch and it worked as a second monitor, but only at 1280x800. My assumption is that this is because the 1st link (which is active because the macbook is single link) is in charge of the odd lines and the 2nd link (which has nothing plugged into it) is in charge of the even lines. Is this true or should it be possible to hack the macbook to output 1920x1200 to the 30"?
 

jeremy.king

macrumors 603
Jul 23, 2002
5,479
1
Fuquay Varina, NC
So I plugged my white macbook to a 30 inch and it worked as a second monitor, but only at 1280x800. My assumption is that this is because the 1st link (which is active because the macbook is single link) is in charge of the odd lines and the 2nd link (which has nothing plugged into it) is in charge of the even lines. Is this true or should it be possible to hack the macbook to output 1920x1200 to the 30"?
Are you mirroring? If so, thats the highest it will go. If you are spanning, then it should go up to 1920, what do your Display Preferences show as available resolutions?

Also, how do you use a display so BIG without running the native res? I got to imagine its pretty fuzzy.
 

natethelen

macrumors newbie
Dec 13, 2006
9
2
I am not mirroring and that is the highest avail res in the list, which is exactly half the pixels wide and half the pixels tall so that is why I am assuming that the way dual-link works is that there are literally 2 DVI connections from the computer to the screen. This would mean that a dual-link video card is not actually required for a 30" to work, but for it to go above 1280x800. It isn't fuzzy because the native res is an exact multiple of the input res.

Mainly I am wondering if in fact this is how dual-link works and therefore I shouldn't even try hacking the macbook.

Thanks,
Nate
 

jeremy.king

macrumors 603
Jul 23, 2002
5,479
1
Fuquay Varina, NC
I think you are oversimplifying it.

You see, half the vertical and horizontal lines is NOT equal to half of the pixels.

1280x800 = 1024000 pixels
2560x1600=4096000 or four times the pixels, i.e. 4 times the amount of information.

I would think that you should be able to get 1920 from a single cable, unless that monitor doesn't support that resolution. The ACD does support 1920, I don't know about the about Dell. Have you tried closing your lid on your MB to see if you can get a higher res?

I seriously doubt you will be able to hack the MacBook to support your monitor, but good luck in your ventures.
 

robbieduncan

Moderator emeritus
Jul 24, 2002
24,638
61
Harrogate
So I plugged my white macbook to a 30 inch and it worked as a second monitor, but only at 1280x800. My assumption is that this is because the 1st link (which is active because the macbook is single link) is in charge of the odd lines and the 2nd link (which has nothing plugged into it) is in charge of the even lines. Is this true or should it be possible to hack the macbook to output 1920x1200 to the 30"?
It doesn't anything like that. A DVI link uses TDMS chips, one at each end. These encode the digital signal to send up the wire. In a dual link system you have two chips at each end. They are linked together to enable them to send and receive two unique data signals that do not interfere with each other (as they are out of phase with each other). This doubles the data rate.

In a MacBook there is a single TDMS chip attached to the external output port. Internal displays normally use a different signalling method as they do not need the signal to travel over the same sort of distance so there is no second TDMS chip.

There are no hacks around this. If you want Pro features by the Pro laptop.
 

natethelen

macrumors newbie
Dec 13, 2006
9
2
So to be completely clear, you are saying that no matter what software was written, it is not possible to do more than 1280x800 on a 30" even though the display card can do 1920x1200 on a 23"?
 

robbieduncan

Moderator emeritus
Jul 24, 2002
24,638
61
Harrogate
So to be completely clear, you are saying that no matter what software was written, it is not possible to do more than 1280x800 on a 30" even though the display card can do 1920x1200 on a 23"?
No. I'm saying it's not possible to get Dual-Link running. A single link is good for 1920x1200. If the screen does not report this as a possibility it may be hard to get your Mac to run at that resolution, but might be possible, but the full resolution of the 30" won't be available.

Edit to add the 30" specs page claims 1920x1200 is a supported resolution for the screen. It looks like it should work...