External display (Dell U3425WE) compatibility with Mac Studio (M2 Max)

If you are using a single Thunderbolt cable for both video and down-stream hub..?

Then it sounds like you need to upgrade that cable to an Apple Thunderbolt Pro or after-market TB cable.

https://www.apple.com/shop/product/MDW94AM/A/thunderbolt-5-usb%E2%80%91c-pro-cable-1-m

The other option is to use two cables, one cable for video and one cable for the down-stream hub.

For video use either a short high speed HDMI cable or a short high speed USB-C to DisplayPort cable.

https://www.amazon.com/dp/B09HXPZ1PQ/ref=sspa_dk_detail_2?

https://www.amazon.com/dp/B09NVV76FH/ref=sspa_dk_detail_5?

Dell Support – Dell 3425WE Manuals & Documents

One of the documents here is a guide on how to update the monitor's firmware using a Mac. I don't know whether that means that there is actually any firmware update that would be related to this issue.

Pages 15 through 19 of the User's Guide describe the ports on the monitor, as seen from a bottom view without the monitor stand. There are several ports that use USB-C connectors:

• Port 7 – Thunderbolt 4 downstream port for daisy-chaining
• Port 8 – Thunderbolt 4 upstream port – this is the one that you would want to use to make a Thunderbolt connection to your computer
• Port 9 – USB Type-C upstream port (data only)
• Port 14 – USB Type-C downstream port

The manual indicates that one of the cables included with your monitor is a Thunderbolt 4 passive cable that has a length of one meter. That seems to be the only bundled cable with USB-C connectors on both ends.

the Mac requires an Error-free transmission to the display, else the signal drops out.

that display appears to be a 4K display with 8 bits/color capability (HDR NOT supported)

interfaces include

HDMI 2.1 up to 100 Hz

DisplayPort 1.4 up to 120 Hz

ThunderBolt 4 (could also provide 90 Watts power delivery for a laptop)

USC-C port is data only, not for display data.

You could use a USB adapter to DisplayPort, but the cable length should be one meter maximum.

Slightly better reliability and refresh rates using a Thunderbolt cable, but that cable should be 0.5 meters total length.

HDMI would work, and the data rates provide by the Mac are slightly higher, but the refresh rate supported by the display is slightly less.

HDMI cables you want for HDMI-only Displays (higher resolutions than 720p TV sets) are marked as Certified with an anti-counterfeiting tag and are labeled:

"PREMIUM High Speed HDMI cable" or that + "with Ethernet" (up to 4K at 30Hz) --OR--

“ULTRA High Speed HDMI cable" or that + "48G" (supports higher resolutions and backward-compatible)

Cables with No Certification tags are good for your standard 720p TV set, and not much more.

For this display, you would need to use an ULTRA cable

Grant Bennet-Alder wrote:

that display appears to be a 4K display with 8 bits/color capability (HDR NOT supported)

A UHD 4K display would have a resolution of 3840x2160 pixels.

This display has a resolution of 3440x1440 pixels, and a diagonal of 34.14", for a pixel density of 109.2 PPI – just a hair larger than that of a 27" 2560x1440 display. So it's like someone took a 27" 2560x1440 monitor and made it about 34% wider (17% on each side).

Although the number of pixels is 2/3rd that of a 4K display, the maximum refresh rate is 120 Hz, so overall, we may be looking at 4/3 of the bandwidth requirements of a typical 60 Hz 4K display.

aside to Servant of Cats--

With growing frustration at ONLY the standard timings shown in the Wikipedia article on HDMI, I poked around a little more. There is a reference just above the standard timings tables to footnote 144 -- a GitHub "Video Timings calculator", which was still working when I tried it. That tool is far too obtuse for the general public, but you might like to fiddle with it.

https://tomverbeure.github.io/video_timings_calculator