2017 iMac 27 connecting to external displays

My EIZO monitor is DVI and connected to my old iMac with a DVI to display port adapter. No Tbolt3 to 2 adapter could get it to work with my 2017 iMac. After getting an OWC Thunderbolt 2 equipped enclosure my display connected just fine.

I'm in a similar boat - have newest iMac 27 18,3 maxed out and want to connect 2 Apple Cinema Didplay 23 inch monitors. Has anyone successfully gotten an old Cinema Display to work with a new 3017 iMac?

I would have loved to buy the Apple endorsed 27" LG, but $1700 CDN is a little steep. You're going USB-C to USB-C.

I think the majority of issues are going from a Mac USB-C port to another monitor port like HDMI or DisplayPort.

Both my Apple Cinema Display 23inch are now working with my Mid 2017 iMac 27! I used two StarTech USB-C (24pin) male input to DVI-D (29pin) female output and VOILA - both monitors are working and playing nicely with the 5K, 27 inch. I really didn't expect this to work! But it did. Not sure if this will work with Cinema Displays of larger sizes. Thanks to all the good advice here. Don't give up!

Here is a pic of a 2017 iMac 18,3 driving two 23in Apple Cinema Displays. For a stress test I have macOS Sierra flanked by a monitor running Apple Mac OS 9 on the left and Windows 10 on the right monitor. Speaks to the power of the Radiin Pro 580! I probably should put on sun screen or screen screen. It's bright!!

Thanks. Your set up is what I want to do. But how did you get OS9 to work on this new machine? Or is this screen sharing an older mac? Yes I ordered the StarTech.com CDP2DVI USB-C to DVI Adapter for video resolutions up to 1920x1200 (Black) from Amazon. It is the same model number as the one on the StarTech.com web site.

No screen-sharing. That is a live OS 9 running on the new iMac. I use an emulator called Sheepshaver to achieve that. I have some rather old but important (to me) OS9 software I need to periodically run. For Windows 10 I use Paralells emulator.

Also, I am trying to throw everything I can at this new iMac while I decide if I'm going to keep it or not. So far it looks great !! It's half the price and 6 months (st least), prior to the release of the iMac Pro.

I still have a PowerMac G5 (2005) around with a partition to start up in Tiger so that I can use OS9 Classic for rare occasions. This was the last of the PowerMacs. Still works. Put in an SSD drive and 2GB drive last year. I should be receiving the USB-C to DVI adapters by Monday. Amazon's 2-day shipping turned into almost a week for some odd reason.

Received delivery of one of the StarTech.com CDP2DVI USB-C to DVI Adapters I ordered. Plugged it in. It works! Thank you for the suggestion!

After I order these I found a cheaper version for $19.99 which I think should work. Monoprice Select Series USB-C to DVI & USB-C (F) Dual Port Adapter https://www.monoprice.com/product?p_id=15243

That's great! I am so enjoying the 5k 27 flanked by two ACD 23inchers. Honestly tho, they look a little long in the tooth after 10+ years! But for email screens, Activity Monitor and such, it's fine.

I have a bit of a thing about keeping old hardware and software in service till it literally gives up their ghost. Apple gear really lasts I can attest to that. I love to fire up one of those 17in Powerbooks - that was a hardware high point for sure!!

Thanks for this, I have used this cable to connect my 2017 iMac to my 2009 iMac. I bought the stupid USB-C to Thunderbolt 2 adapter and tried using the Thunderbolt 2 to Thunderbolt 2 cable to connect the two, but nothing! What a waste of a WAY over priced adapter!

Just wanted to chime in and say the StarTech USB C to DVI Adapter (CDP2DVIW) didn’t work with my 27” iMac (2017) and Dell 23" S2340M.

Previously I was using the Dell with a 27” Mid-2010 iMac and a StarTech Mini DisplayPort to DVI Adapter (MDP2DVIW). No issues there.

I’ve reseated the cables and adapter, powered the monitor off and on and restarted my Mac (including a safe boot) but it will not see the monitor.

I then picked up an Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 adapter to use with the DisplayPort to DVI Adapter. Again … nothing. At least I can return it ($59 CDN. Ugh.)

I’m going to try a few other cables that others have reported having success with. This really seems to be a hit or miss thing, and it shouldn’t be.

I have the identical iMac setup. Im trying to connect my Benq RGB photo monitor. Ive bought the Thurderbolt C to display port cable but the Benq monitor is dead. System preferences only shows the native 5k monitor. Did you learn anything that could help me. I would appreciate any help.

I suspect the Apple store staff are not fully up to speed on all the adapters and this particular issue with the 2017 iMacs. They recommended the TB2 to TB3 adapter.

I did contact StarTech and they were unable to diagnose.

The USB-C to HDMI adapters get mixed reviews on Amazon, with a few people saying it didn't work with their 2017 iMacs. I'll keep this bookmarked, however. I have two more cables arriving tonight. It's a crap shoot, and I'm hoping one of them will work. If not, I'll be contacting Apple support. From what I understand, they do not read the forums. Perhaps if enough of us complain, they'll address the issue.

The Belkin adapter does specifically say it supports the 2017 iMac.

"COMPATIBILITY

Google Chromebook Pixel

MacBook Pro (2016)

iMac (2017)

Dell XPS 13”

Another combination that should work (does not need DisplayPort ALT mode) is a USB-C to Mini DisplayPort adapter followed by an ACTIVE Mini DisplayPort to DVI adapter.