iMac VGA out???

in Current Mac Hardware edited January 2014
The 15" iMac has its VGA output tied to the resolution of the LCD ( I think ).

This follows fairly straight forwardly from the fact that the GF2mx has an internal TMDS and CRTC. Im guessing that Apple just used both outputs because it was convenient.

However, the GF4 mx has two sets of TMDS' and CRTC's, and the tech specs states that the video out is still bound to the limits of the 15" model.

What are the odds that on the 17" the vga output is actually a real second video out ( no extra cost, its built into the chip ), and it will only require a driver modification to enable it properly????


  • Reply 1 of 3
    jasonppjasonpp Posts: 308member
    after seeing some hacks around the web that forced an iBook to san instread of mirror at resolutions up to 1980x1200ish, I would have to disagree

    Apple disables spanning in software. This is a dirty trick.

    Bad Apple!
  • Reply 2 of 3
    woozlewoozle Posts: 64member
    Well, the iBook doesnt use a geforce mx, so its not really a valid comparison. Im not sure exactly what the ati rage in the ibook can do.

    I believe ( from everything that Ive read ) that the gf mx has one on board display generator - it has outputs for TMDS, analogue, and video. To get a second display and external ramdac needs to be added. Apparently you can get dual tmds ( DVI ), but it isnt clear if this is on chip, I think a second external tmds transmitter needs to be added.

    This leads me to believe that Apple is taking advantage of the fact that two identical outputs are generated by the gf mx, the digital goes to the lcd screen, and the analogue goes to the external port. Its a bit of cheapness ( not putting the external ramdac in for the second port ), but fair enough.

    The gf4 mx used in the 17" iMac has dual display paths built in, full TMDS, analogue, and video. This means that Apple dont need to add any extra hardware, and they could have real dual output. It seems even more possible, because the vga out generates the standard 15" resolutions ( according to the tech specs ). This would require setting up the second display generator to handle those, while the internal screen runs at its resolutions.
  • Reply 3 of 3
    bodhibodhi Posts: 1,424member
    Off to Current Hardware you go....
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