2023 iMac - M3 Chip - External monitors

DGHanna wrote:

Curious if anyone has 2 external monitors working with a 2023 iMac (M3 chip) - just bought this iMac, not thinking it was even possible in today's world to have a machine that doesn't allow more than 1 external display!

The specifications of that Mac clearly state that it supports one external display. It can be a very-high-resolution (5K or 6K) one, but there can only be one. The iMac already has a high-resolution built-in display, so that means you can have a total of two displays, when you count the built-in one.

If you do - can you please provide the device needed to make this work?

There are no devices or applications that can add more first-class, hardware-accelerated video outputs. Those require hardware support in the Apple Silicon processor itself. The base M3 chip in the 24" M3 iMac supports a maximum of two active video outputs, and the iMac's built-in screen consumes one of those.

There are workaround products that can let you attach more displays in a second-class way, using workaround technologies such as DisplayLink. These may have drawbacks such as

• Reduced display quality (lags and artifacts)
• Video from DRM-infested streaming services not playing on your additional displays – or possibly not playing even on your iMac's built-in display as long as the workaround is active
• The possibility that the software which enables the workaround will break when new versions of macOS come out, forcing you to rely on a third-party vendor for a fix

OWC and SonnetTech have "dual HDMI" DisplayLink adapters; SonnetTech has a "dual DisplayPort" DisplayLink adapter; and there are a raft of low-end hubs with DisplayLink or similar technologies.

These are some of the workaround products previously mentioned. If you want the extra space for spreadsheets (which are relatively static), lags and artifacts might not be as much of an issue as they would be for applications like editing movies or running high-end games.

Other World Conputing – OWC USB-C Dual HDMI 4K Display Adapter with DisplayLink

SonnetTech – DisplayLink Dual HDMI Adapter for M Series Macs

SonnetTech – DisplayLink Dual DisplayPort Adapter for M-Series Macs

These particular ones use DisplayLink.

Synaptics – DisplayLink Graphics

DisplayLink KnowledgeBase – Troubleshooting: macOS

Sorry, only one display:

iMac - Technical Specifications - Apple

I guess you can only fit so much GPU into the chip

In addition to the Hardware Spec's that Keith posted, see > Connect an external display to your iMac - Apple Support

Keith Barkley wrote:

Sorry, only one display:

I guess you can only fit so much GPU into the chip

The base M1, M2, and M3 chips are entry-level chips.

As you move up the ladder to Pro, Max, and Ultra chips, you get more hardware computing units of various sorts (CPU cores, GPU cores, video encoding/decoding engines, I/O controllers, display controllers).

BTW - Apple support claims I can get two externals working by daisy chaining off Thunderbolt 4 (I don't believe that though and didn't want to go through expense / returns to try without trying this forum first). Thanks again.

That statement is (mostly) true, but misleading.

Your iMac does not have Thunderbolt 4 ports. One of the requirements for Thunderbolt 4 certification is the ability to drive two monitors over USB-C (DisplayPort) or Thunderbolt. Your Mac has Thunderbolt 3 ports. Thunderbolt 3 equipped computers are allowed to support multiple monitors (some Intel Macs do), but it is not a requirement.

If your Mac had a Thunderbolt 3 or Thunderbolt 4 port, and was capable of driving multiple external monitors, then the only way to drive two monitors off a single Mac host port would be to connect them through Thunderbolt. E.g., Mac to Thunderbolt dock, and then plug both monitors into that dock. A Thunderbolt connection provides a wider data "highway" than a plain USB-C (DisplayPort) connection would.

Even then, you would not necessarily be "daisy chaining off Thunderbolt 4". A much more likely setup would be for you to have two non-Thunderbolt displays or adapters plugged into the Thunderbolt dock. The Thunderbolt dock would be distributing two video signals between two displays, but neither display would be "daisy-chained" off the other, or would even be aware that Thunderbolt was involved.