Cinema Display 23" (A1082) with iMac 21.5" 4K 2017 (A1418)

[Faloude]

The Cinema Display 23" (model no.: A1082) should work fine with an iMac 21.5" 4K 2017 (model no.: A1418) right? I've connected it like this: DVI cable from Cinema Display -> DVI to Mini DP adapter -> Mini DP to USB-C. Unfortunately the Cinema Display is not detected. Should I assume the problem is the "double adapter" setup and just get a DVI to USB-C adapter?

For clarity: the iMac has no Mini DP port but instead 2 thunderbolt ports (in USB-C format).

 

[Amethyst1]

Should I assume the problem is the "double adapter" setup and just get a DVI to USB-C adapter?

Yes.

It's likely that the miniDP-to-DVI adapter is "passive", i.e. requires the computer to detect that a DVI adapter is connected and output a DVI signal instead of a DisplayPort signal. The twin-adapter setup may prevent that.

 

[xraydoc]

The Cinema Display 23" (model no.: A1082) should work fine with an iMac 21.5" 4K 2017 (model no.: A1418) right? I've connected it like this: DVI cable from Cinema Display -> DVI to Mini DP adapter -> Mini DP to USB-C. Unfortunately the Cinema Display is not detected. Should I assume the problem is the "double adapter" setup and just get a DVI to USB-C adapter?

For clarity: the iMac has no Mini DP port but instead 2 thunderbolt ports (in USB-C format).

What miniDP to USB-C adapter are you using? I'm betting the issue is there.

 

[Faloude]

Yes.

It's likely that the miniDP-to-DVI adapter is "passive", i.e. requires the computer to detect that a DVI adapter is connected and output a DVI signal instead of a DisplayPort signal. The twin-adapter setup may prevent that.

Interesting. I'll give this a try and report back.

What miniDP to USB-C adapter are you using? I'm betting the issue is there.

Why would you bet on that and not the double adapter setup? It's some unknown brand with good reviews (A-Konic).

 

[xraydoc]

Why would you bet on that and not the double adapter setup? It's some unknown brand with good reviews (A-Konic).

I don't know anything about that particular one, so I cannot comment on it specifically, but others have tried to use the Apple TB2 to USB-C adapter, thinking it'll work. Since the ports physically are correct, several have mistakenly purchased it, thinking it would work. But despite the correctly fitting connectors, it works only with TB data and not DP video.

But if both adapters are reportedly good, then the combination of the two is likely then the cause.

 

[Amethyst1]

But if both adapters are reportedly good, then the combination of the two is likely then the cause.

I did some research and it seems "all" USB-C port implementations can only output DisplayPort signals via Alternate Mode, not DVI/HDMI (TMDS) signals, even though there is a specification for HDMI Alternate Mode.
Thus, daisy-chaining a passive miniDP-to-DVI adapter (which needs a TMDS signal) to a USB-C-to-miniDP adapter isn't going to work. An active USB-C-to-DVI adapter which converts DisplayPort signals to DVI/HDMI (TMDS) signals is necessary.

 

[Faloude]

@Amethyst1 seems correct! The new USB-C to DVI adapter works perfectly.