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My MacBook Air Early 2014 has a thunderbolt port. According to this article thunderbolt supports dual-mode DisplayPort (DP++), which in turn supports passive converters.

So theoretically I can buy a passive mini-displayport to HDMI or DVI converter, and connect to my monitor and it should work. Is this assumption correct?

I ask because I bought two converters, one for HDMI and one for DVI, but neither of them worked. My monitor just does not detect any signal. So I want to double-check my assumption.

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    Always use an active adapter. HDMI and DVI are very different, especially the clock signals. – Allan Apr 11 '18 at 15:57
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The asker's own answer clarifies that a BenQ BL2420PT monitor was what wouldn't work with the passive adapters. That monitor has a native resolution of 2560x1440, which requires either DisplayPort, dual-link DVI, or HDMI 1.3+ (the monitor might still work with single-link DVI or HDMI 1.2− if the MacBook is set to output a resolution of 1920x1200 or lower):

  • The MacBook Air (Early 2014, both the 11-inch and 13-inch models) supports up to 2560x1600 over DisplayPort. So if the DisplayPort input on the monitor isn't already occupied, the cheapest and/or least confusing solution might be to use a Mini DisplayPort to DisplayPort cable.

  • Passive DisplayPort to dual-link DVI adapters do not exist due to DisplayPort's limited number of pins. There are active DisplayPort to dual-link DVI adapters available, and these require the use of a dual-link cable:

DVI-D connector types

  • For HDMI, there are both active and passive adapters available which support HDMI 1.3+, however one vendor adapter (Plugable) claims:

    When outputting a TMDS (DVI/HDMI) signal through Dual-Mode, most DisplayPort sources as well as the inexpensive passive adapters on the market are limited to a 165MHz clock rate. This limited clock rate generally limits the maximum resolution to 1920×1200 and reduces the maximum available color-depth to preserve the limited bandwidth.

    Some mid-range DP -> HDMI adapters such as the Plugable MDPM-HDMIF are capable of operating at up to 300MHz, but ultimately they are still reliant upon the Dual-Mode functionality of the host to transmit the TMDS signal required for HDMI/DVI displays.

    So your passive HDMI adapter might be one that is limited to 1920x1200. Nor is it clear from the many existing questions on this topic whether the MacBook Air can output more than 1920x1200 over dual-mode DisplayPort.

to name a few: Can a MacBook Air support 2560x1600 output via HDMI using a Mini DisplayPort/Thunderbolt to HMDI adaptor?, MacBookAir 2014 MiniDP to DP 2560x1440, 2013 Macbook Air not showing 1440p Option on External Display, What's the max resolution for mini DisplayPort connected to a 2013 MacBook Air?, HDMI with resolution 2560 x 1440 possible?. Found using combinations of "macbook air", "displayport to hdmi", "passive", "dual mode" "2560x1400", "1440p", etc. Unfortunately many of these contain anecdotes, conflicting answers, or misleading advice (like forcing certain graphics or adapter hardware beyond specified limits, preferring HDMI over DisplayPort, etc.).

  • Thanks for the detailed answers. I have also updated my new findings in my own answer. – lulalala Apr 13 '18 at 6:51
  • DisplayPort to dual-link does exist. See: apple.stackexchange.com/questions/297704/… and – Allan Apr 13 '18 at 12:56
  • @Allan correct, active DP to dual-link DVI adapters exist, but not passive ones. USB-C to dual-link DVI adapters such as the Tripp-Lite adapter in your link are active, since USB-C still does not have the data pin count required for passive dual-link DVI output. – chrstphrchvz Dec 29 '18 at 20:49
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I tried my two miniDP converters on two other monitors. Both worked fine.

So at the end I think it comes down to that passive adapters will work on less sensitive monitors. The more sensitive monitors (such as my BenQ BL2420pt) will not work.


Update

Somehow, very rarely, my dvi converter works on my monitor. It would display 1920x1080 on it. I assume it only rarely work because the signal happens to be detectable by the monitor (e.g. voltage?)

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