Actually, it shouldn’t be a problem to connect Thunderbolt 3 to DVI. If the cable is NOT permanently attached to the monitor, then a cable like this should work. If the cable is permanently attached so that it is meant to be plugged directly into the computer, then you need to add a gender changer like this.
Note these simply came up high in the list when I searched on the web for ‘Thunderbolt 3 to DVI’ and ‘DVI Gender Changer’. There may be others that are better or cheaper.
I’ve got a 30" Dell monitor attached to a 2017 MacBook Pro. Recent thread:
As @foo wrote, if your display requires dual-link DVI, then you need an active adapter that can generate signals for both links. You can get DisplayPort/miniDP adapters for dual-link DVI, but since they are not passive cables, they tend to cost a bit more and may also require a power supply.
With a single link, DVI is going to top-out at about 1920x1200, which is a much lower resolution than Apple’s 30" display and is probably lower than most 30" displays.
Apple’s ADC connector (which combines DVI, USB and power onto one cable) can be used, but again, it’s not a cheap adapter. In order to connect an ADC monitor to a modern computer, you need an adapter that can supply the display’s power and connect its USB (since the display’s controls are adjustable via software over this connection). Apple once made the adapters, but they may be hard to find today.
If you have 30" displays from other vendors with other ports (e.g. HDMI or DisplayPort), then you can probably connect it with a cheap passive cable because these technologies support the higher resolutions using a single link.
i’m also grimly hanging on a 2014 imac hoping it survives until the mooted release of the 27in+ imac. its screen has all sorts of artefacts (mostly burn-in from gmail). certain things no longer work as expected but that i’ve got 6+years of service from this machine is most excellent (its predecessor failed after only 4years).
got my fingers crossed that @dave6 is correct about the fall. earlier would be better but as long as it’s the fall, okay …
For me the one key differentiator between iMac vs Mac Mini+external monitor was the availability of decent graphics cards for the iMac.
The relationship between the M series processors and graphics cards is still emerging of course, the initial release is a clear replacement for Intel processors + intel graphics. Whether and how more advanced processors work with external graphics cards is yet to be seen.
@suoakesdesign
I would recommend using an external SSD … but not the common USB 3.0 type (commonly known as SATA connection).
I now use the Crucial P1 1TB 3D NAND NVMe PCIe M.2 SSD with a Simplecom SE503 M.2 NVMe SSD to USB 3.1 Gen 2 Type C Enclosure. (It comes with 2 cables, one USB, and the other for Thunderbolt/USB-C connection).
The Thunderbolt 2 slot on your iMac is 20Gbps. The common external USB 3.0 connected SSD is 5Gbps. Basically Thunderbolt 2, using a PCIe SSD, is 3-4 times faster for Read & Write operations compared to an external SSD connected to USB 3.0.
(Both of those are faster than your spinning internal hard drive).
The cost for these two items is about USD$100-$120 total. You can pay more for a similar thing on OWC etc, but you should be able to order these from a PC components supplier.
You have enough RAM. Adding more would not benefit you much on that iMac. However, using an SSD would be a huge benefit.
TIP: Clone your hard drive onto the new disk using Carbon Copy Cloner. Then boot from the SSD connected into the Thunderbolt port.
When (in a year or so) you have purchased a new iMac to replace the 2014 one, the external SSD can be used as a very fast “transporter” disk.
Note: Getting a higher spec’d NVMe is a waste of $$$$ as the throughput of the port can’t handle the higher speed of those SSDs.
As Steve Jobs used to say … “One More Thing….” Your longevity in the tutoring arena may benefit from also becoming an instructor in the Affinity suite of apps (Affinity Photo; Affinity Designer; Affinity Publisher).
The Affinity apps run “buttery smooth” on Intel Macs and the Photos & Designer app run on iPads. The price is unbelievably low … and no subscription required. Check it out on the App Store. (Photos also has been featured in some recent Apple Event Keynotes).
Perhaps someone already said this, but you don’t have to use an Apple display with a Mac. Apple displays look nice but they are too limited for many purposes–not enough inputs or different connections, and some only turn on when triggered via TBolt. There are plenty of great displays out there that will work just fine with any Mac (and be generally more useful). Don’t let the display limit your options!
My thinking is that, like LaserWriter printers and Airport routers/storage, Apple never wanted to be in the freestanding display business. They only develop unique products, and they only do so do so when they recognize a demand that isn’t being met. That’s why there’s only a super expensive Pro Display XDR display and an an equally super expensive and very unique fancy stand. There are only two high end LGs that are not nearly as high end as the Pro for sale at the Apple Store. High quality, and products and services that work well together are hallmarks of Apple’s brand image.
My husband and I both have Samsung monitors we bought at least a decade ago and we have been very happy with them.
I hope nobody here is assuming otherwise. This part of the thread was in reply to @helmutr who (I think) was trying to find a way to keep using several old Apple monitors that use connectors no longer provided by Mac computers (ADC and DVI).
And the answer is that adapters exist, but in this particular case, they may be expensive and/or hard to get.
For someone looking to buy a monitor for a modern Mac, they all have USB-C ports and some have HDMI ports as well. These can be used with inexpensive cables/adapters to drive monitors that use HDMI, DisplayPort (mini or full-size), single-link DVI and VGA ports.
Which means you can go to any store that sells computer displays and pretty much use any model they sell. You can also use a TV (definitely a 1080p HD TV, and probably also a 4K TV) via HDMI. But you may find that computer displays provide a better picture.
Personally, I would recommend looking at the least expensive display that has an IPS panel and the size/resolution you require, then read some reviews to see what people think of them.
I wouldn’t even look at an Apple monitor. If you need something like that, then you probably shouldn’t be asking me about it. 
For myself, I’ve been buying Dell Ultrasharp monitors. They’re not the cheapest, but they’re good quality and they last a long time. The one on my main computer (a Dell 2405FPW) is over 15 years old, is attached to its third computer and is still working great.
At that time, in 2017, Apple told me flat out that it can’t be done, that that 30" cinema display can’t be connected to the new iMac. I tried several adapters that were offered on the market at that time. They were adapters in the sense that they had the right connector, i.e. I could plug them in, but they didn’t work. I guess they didn’t convert the signal properly. It should have been easy for Apple to make a connector available. Why not?
On another front, when I brought my 2011 iMac for repair in 2017, I was told that they don’t repair that machine anymore, because it is “vintage”.
Which reminds me of a time when you didn’t have so many choices, so many brands and so many models. If you wanted to have a phone, you couldn’t even buy one, only rent it from the phone company. But that also had side effects: the phone never broke.
I was mainly concerned about the original poster, who was thinking about getting a Mac Mini and seemed to suggest that it had to have an Apple monitor. I’ve noticed that sometimes people are stuck on the idea that all Apple stuff is unique (I once saw a post from someone who needed a USB mouse and thought it had to be Apple). Admittedly, Apple does have a tendency to do things their own way in some cases which can be quite annoying!
I also spec Dell Ultrasharps in many situations and am looking at one now.
Well, the person you spoke to was wrong. The 30" Cinema Display uses an industry-standard dual-link DVI interface. He probably meant so say that Apple doesn’t sell the kind of adapter you need.
The problem is that the overwhelming majority of DisplayPort/USB-C DVI adapters are single-link and the 30" Cinema Display requires a dual-link adapter. You can’t tell a single-link from a dual-link adapter by looking at it because both use the same connector. The difference is that a single-link adapter only sends data on half of the pins, which isn’t enough to drive a display beyond 1920x1200 resolution.
A web search for dual-link adapters found this Amazon listing as the first hit: USB C to Dual Link DVI Active Adapter. Its reviews (which involve a 30" Cinema Display) are mostly positive, although some reviewers did report image quality problems.
Yep. Any Apple product is declared “vintage” 5 years after it is discontinued. This means they provide no service or support, except in California, where the law requires support for 7 years. After 7 years (from when it is discontinued), it is declared “obsolete”, which means there is no support in any location.
See also: Obtaining service for your Apple product after an expired warranty - Apple Support
According to Mactracker, the Mid-2011 iMac models (introduced in May 2011) were discontinued in October 2012. So they became vintage in October 2017 and obsolete in October 2019. Looks like you just missed the end of the repair window for that model.
I haven’t been in the market for a long time–what is the availability like for retina-quality resolution on monitors from Dell or other vendors? None of the PC monitors I’ve run into for work have gotten away from the standard pre-retina resolutions, so I really don’t know what’s out there.
Thanks!
Dave
Dell’s web site lists 23 UltraSharp models. Looking at the pixel pitch, the highest DPI displays (sorted by DPI and screen size) are:
Whether you consider these “retina” at normal viewing distance (which for me is about 24" away) is up to you. I assume everybody would consider the 32" 8K display to be “retina”. I would consider the others a matter of debate.
(I don’t know if any Macs can drive an 8K display. Apple only advertises up to 6K support).
Their other UltraSharp displays are around 100-110 DPI, which are probably not going to be “retina” for most people.
I can’t speak specifically to Retina equivalency, but start by looking at displays that do 4K or
higher (3840x2160 or more). Narrowing down is a matter of what your primary usage will be (text,
graphics, photo/video, etc.), which will affect some of the other parameters. My wife, for example,
has a BenQ display that came factory calibrated for photo work. Read some reviews… I guess one
advantage of buying Apple is that you don’t have to make a lot of choices to get a very nice
display. The downside is irritating the limitations and quirks (like trying to put one on a VESA
mount) and the cost.
– Eric
My 2015 iMac 27" with 32GB RAM & an internal SSD (1 TB) was taking a full 1 minute to open Adobe CC Illustrator or InDesign from Bridge. Replaced it earlier this year with a 2018 Mac Mini with 64 GB RAM and 1GB SSD. Those Adobe CC apps now open in under 10 sec, with big files stored in an external RAID 1 with 2 x 2 TB spinning platters & connected via TB3.
If push comes to shove with your existing iMac, then the 2018 Mac Mini should surely get you a performance lift. I’ve never yet seen anyone complain about having a second monitor for when the M1X iMac is shipping.
Indeed. The Dell U2720 series is excellent. I have used its two immediate predecessors myself at work and I would have zero hesitation to go for it again.
My boss just got a new U2720M (same as the Q, but ships with HDMI cable instead of DP) a couple months ago and he’s in love with it.
It’s a great panel in a shitty ugly plastic case at a good price. IMHO the kind of screen Apple should be selling, in a proper metallic enclosure of course. But they never appreciated multiple inputs or height/swivel adjustment so in all likelihood it would be lost on them. 
I run two Dell P2715Q 4K, 3840 x 2160, monitors on my M1 Mini just fine. Unless you really need intel go for the M1 now. My old 2019 32GB MBP i7 is not really missed now that I don’t need to travel and I am sure when I do there will be options if not an M1 Air will do fine.
fApple’s history is that they very rarely announce products at WWDC unless there is some related software. Much better for them to announce things in another week when there are no distractions from software that they have announced at WWDC.