Question for 30" display owners

Discussion in 'Macintosh Computers' started by nagromme, Feb 14, 2005.

  1. nagromme macrumors G5


    May 2, 2002
    What resolutions do you see in System Preferences > Displays? (Option-F15)

    I'm contemplating a PowerMac with display, and Apple's specs pages only list SOME of the supported resolutions for their displays.

    Thanks in advance!

    (I could swear I posted this already today, but it's gone. Weird.)
  2. Bear macrumors G3

    Jul 23, 2002
    Sol III - Terra
    Your best bet if you want to use other than the optimal resolution for the display is go into a store that has one and look. A lot of the non-optimal resolutions don't look very good at all.

    I has a 23" HD Display and I always run it at 1920x1200.
  3. nt5k macrumors newbie

    Feb 14, 2005
    The highest resolution that I was able to get using a PB w/ 64mb vram was 1200x800 or so.

    Going to 1920x1200 seems to require a dual-link dvi setup if I am not mistaken..
  4. edesignuk Moderator emeritus


    Mar 25, 2002
    London, England
    You are mistaken...I think! Previous gen PBs with single-link DVI could power the 23" displays (1920x1200), IIRC.
  5. Logik macrumors 6502a

    Apr 24, 2004
    correct.. DDVI is for the 30" only... and any previous generation powerbooks could handle anything less than the 30" but not including the 30".. the new powerbooks have the option to drive the 30" with DDVI...
  6. nt5k macrumors newbie

    Feb 14, 2005
    Then how come the PB won't allow me to go to 1920x1200 on the 30" display?
  7. edesignuk Moderator emeritus


    Mar 25, 2002
    London, England
    I don't know really, perhaps because the technology is just different (S-DVI vs D-DVI?). I really don't know too much about it, but I'd expect that is why.
  8. Logik macrumors 6502a

    Apr 24, 2004
    you simply cannot drive a 30" on a powerbook or machine that doesn't support DDVI ... at least this is my take on it.
  9. nt5k macrumors newbie

    Feb 14, 2005
    Define 'drive'.

    If you mean you can't use the display at all, that is just wrong.

    If you mean use it at its full resolution, than you would be correct.

    Well, I am only commenting because I actually have a 30" HD hooked up to a 17" PB and it does work, but I can't go above 1280x800. And neither can my pc, despite setting the video to 1920x1200.
  10. nagromme thread starter macrumors G5


    May 2, 2002
    I know that only the native res would be ideal, but I'd like to know the specific modes that the 30" supports. (My local store has none or I'd check myself.) BTW I already have the mode list for the 23" if anyone wants it.

    (But thanks for clearing up that older-PowerBook question--I was wondering about that too :) )
  11. Logik macrumors 6502a

    Apr 24, 2004
    ok.. doing a bit of math i have come up with THIS idea... whether it is correct or not is not really something i am sure of.. but it might give you an idea

    ok.. Dual DVI is.. dual right? meaning 2, the resolution of a 30" display is:

    2560 x 1600 = 4,096,000 pixels
    if dual is.. dual.. 4096000 / 2 = 2,048,000 pixels per "link"

    let's say you want to drive that display at the same resolution as a 23" which is:
    1920 x 1200 = 2,304,000 pixels .. this is MORE than one channel can handle

    see.. 2,304,000 - 2,048,000 = 256,000 ... too many pixels to be exact.

    1280 x 800 = 1,024,000 * 2 = 2,048,000 or the same as each "link" of D-DVI

    meaning you can power 2 displays at 1280x800 ... but only because that's the most number of pixels each link can pump out.. together however, they pump out enough to cover a 30" display running at 2560x1600... the math seems to make sense to me.. see if you can follow it
  12. nagromme thread starter macrumors G5


    May 2, 2002
    A good theory, but a conventional DVI link can handle more than 1280x800. 17" displays or the 23" Cinema Display (1920x1200) are examples.

    I believe I have read that the 30" is not at the maximum a dual link can handle, though, so with the right combination of equipment, maybe there is a limit like you describe. But I think it would be something 1920x1200 or higher if so.

    Then again, if for some reason the circuitry in the 30" has a reduced limit, maybe each "half" of the dual link connection IS inferior to a normal single link--and what you describe might be so!
  13. Logik macrumors 6502a

    Apr 24, 2004
    bzzzt wrong...

    according to the DVI spec 1280x1024 is the max resolution that one dvi link can handle.

    let's just say i was pretty close in my math :p
  14. Logik macrumors 6502a

    Apr 24, 2004
    ok now we're getting somewhere. the hardware related issue is with the 30" display. it is setup to take in 1280x800 per link, as such it is limited to that if you only have a single link connected.

    what appears to happen with the single link displays and cards is that one of the pins transfers an extra 8 bits (i think) which makes up for the difference in resolution.. still searching for a real definitive answer here
  15. nagromme thread starter macrumors G5


    May 2, 2002
    That link you posted seems to go to a product with two separate conventional DVI links--for two displays at once. That's different from dual-link DVI.

    And the limit they mention for each single connection is just the limit for that particular board when running two displays at once. (Other setups can handle higher res than that with just one conventional DVI connection.)

    Anyway, I'm curious to know the details of this :)

    But even more curious about my original question :) if anyone runs across a full list of modes. (For instance, Apple's specs don't list ANY 4:3 modes like 1024x768, and yet the 30" can of course handle them--probably with your choice of stretched or not. Important for gaming, where sharpness isn't always critical. And also important for a project I'm developing.)
  16. Logik macrumors 6502a

    Apr 24, 2004
    that is actually correct. 2 links.. DUAL DVI... the spec says that each link can drive it's own display, OR drive one much larger display.
  17. nagromme thread starter macrumors G5


    May 2, 2002
    But the term "Dual Link DVI" (which is required by the 30") means something specific and different. Dual Link does NOT refer to driving two displays.

    A Dual Link DVI connection uses one SINGLE connection. That board you link to has the option of an adapter cable providing two "non Dual" ports--but they are more limited than the single-DVI connections of other boards. (EDIT And I see that that's what you mean when you quote "Dual DVI" without the "Link" part :) )

    Note that the 6800 board Apple sells for 30" displays has TWO DVI ports, and EACH of them is Dual Link, so it can drive TWO 30" displays. Dual dual :)

    The X800 on the other hand has just one DVI port--but it's a Dual Link port and can drive the 30". (Plus it has an ADC connector to drive an older display at the same time.)
  18. Logik macrumors 6502a

    Apr 24, 2004

    do you have both a normal dvi cable and the "ddvi" cable handy? take a look at the difference in pins... like i said.. each cable is capable of carrying dual link, the point is the single link cables do not use all the pins. if you compare the two you will see.. as such it's only using "HALF" the bandwidth it has available...

    here let me try to break it down.

    one dvi link is capable of 1280x1024 resolution

    to get more than that resolution another pin has to be used to transfer the extra load...

    so.. it uses essentially 2 links. not in full mind you, just using part of one link and all of the other.

    a dual link dvi uses all the pins and is capable of the full bandwidth.. but if you plug a dual link dvi cable into a single link dvi cable not all those pins are in use... which means she is only transfering half the bandwidth to the display.. since the display splits the links in half... so that each link does half the job... single dvi = 1280x1024... hence.. that's all you get...
  19. nagromme thread starter macrumors G5


    May 2, 2002
    Thanks :) Very interesting.

    (But I do note that a single, conventional DVI connection can handle more than 1280x1024. Not necessarily true of "half a dual link" though.)
  20. wrldwzrd89 macrumors G5


    Jun 6, 2003
    Solon, OH
    Remember the rumor about a 40 inch display from Apple on MacOSRumors? Apparently, the 30 inch display is big enough to require dual link DVI, but doesn't come anywhere near its limits. A 40 inch display WOULD be close to the limits of dual link DVI. Its resolution should be around 3360x2100 assuming 100 pixels per inch.
  21. Logik macrumors 6502a

    Apr 24, 2004

    for one, i'd like to thank you for this exchange.. seriously. i had fun looking this information up. i didn't realize how it was done and now i think i understand exactly what's going on in terms of how and why.. not the low level stuff so much but at least why and how it functions the way it does. and without this back and forth i would not have understood it or at least come up with how this all works otherwise.

    yes, DVI can handle more than 1280x1024 but it uses another pin or two .. let me find that link...

    at least i think that is relevent. again though i'd like to thank you for this, it was a lot of fun looking it all up! i haven't had that much fun testing my google-fu in a long time lol and it's kinda humorous that my original math explaination ended up being pretty much correct... since each link was transfering half the data.. it limited it to the 1280x800 resolution. very cool!
  22. RAS admin macrumors regular

    RAS admin

    Sep 4, 2004
    Berkshires, Mass.
    2560 x 1600
    2048 x 1280
    1920 x 1200
    1856 x 1160
    1792 x 1120
    1600 x 1200 (stretched)
    1600 x 1200
    1600 x 1000
    1344 x 1008 (stretched)
    1344 x 1008
    1344 x 840
    1280 x 960 (stretched)
    1280 x 960
    1280 x 800
    1024 x 768 (stretched)
    1024 x 768
    1024 x 640
    800 x 600 (stretched)
    800 x 600
    800 x 500
    640 x 480 (stretched)
    640 x 480
  23. nagromme thread starter macrumors G5


    May 2, 2002
    Many thanks!

    That's a LOT of modes--and no small amount of work to answer my question!

    But very helpful! I was never going to guess some of those. (Like 1856 x 1160 and 1344 x 1008.) Others I might have guessed but confirmation is important.

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