Issue in setting up dual monitor with Macbook PRO M4 PRO

MacBook Pro Display Support

M4 Pro

• Simultaneously supports full native resolution on the built-in display at 1 billion colors and:
• Up to two external displays with up to 6K resolution at 60Hz over Thunderbolt, or one external display with up to 6K resolution at 60Hz over Thunderbolt and one external display with up to 4K resolution at 144Hz over HDMI
• One external display supported at 8K resolution at 60Hz or one external display at 4K resolution at 240Hz over HDMI

MacBook Pro (14-inch, M4 Pro or M4 Max, 2024) - Tech Specs - Apple Support

your large Dell display appears to be a 5K display with resolution 5120 by 2160 and 10 bits/color for Billions of colors. That is a huge amount of data.

• features ThunderBolt input (cables MUST carry the ThunderBolt trademark) for full resolution support.

• features HDMI input for full-resolution support, PROVIDED you are using certified ULTRA cables. No other cables, such as PREMIUM cables will give acceptable results.

• if you want to use 30 Hz or possibly a lower resolution, can be connected using USB-C directly or with USB-C adapter/cables. All use of USB-C only cables and adapters will result in lower resolution or no picture.

• There is NO HOPE of chaining another display on the same cable -- it is already full with this display's data.

Your Samsung display appears to be a 1920 by 1080 display with 8 bits/color,

• HDMI input ONLY. A PREMIUM HDMI cable would suffice, or an adapter/cable to HDMI or an adapter to HDMI and cable could be used. These adapters are not quite trivial, and may be on the expensive side. Apple offers theirs for about US$70.

The Mac does not use side-loaded Windows "Drivers", which are actually pre-packaged bundles of settings for a specific display. Instead, it asks the immutable source -- it queries the display, directly. That is how it knows the identity (and capabilities) of your display(s) without you ever typing them in.

Communication is the ability of the speaker to create a picture in the mind of the listener. If that picture does not form properly, it is not always the listener that is at fault.

I cannot see your setup, and can ONLY rely on your words, which I found less than clear.

You did not specify ANY of the exact cabling setups you used, only a list of ports and a list of displays. I was addressing the most extreme case (since you did not rule it out) to be sure you knew you could not plug them into each other.

How are you connecting the cables (and what cables are you using) when you try to run both displays at once? Please be very specific, I can't see any of what you try.

The Mac does not rely on windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

so try doing some of those things and see if the display comes alive.

<< 2... this display also worked, but catch is, it is not giving max output, it's working at 5k smoothly but, refresh rate get limited to 60hz.>>

Then your Mac is operating as designed. That meets the specifications of the ThunderBolt computer output.

In theory, it could go as high as 98 Hz refresh, but I do not think the standard Mac software will run at that refresh rate.

The hardware does not "trade" refresh rates from one display to a different display. Decreasing the refresh rate on the built-in display will have no effect on other displays.

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The Mac asks the display to report any transmission errors when sending data to the display. it will NOT operate above a data rate that is error-free.

It is conceivable, but not guaranteed, that a certified ThunderBolt cable limited to 0.8 meters, or an ACTIVE Thunderbolt cable (has signal re-drivers and signal-conditioners, so is expensive, typically Over US$100) MIGHT be able to attain slightly higher refresh rates, possibly as high as 144 Hz.

The Apple Support Communities exists to help ALL users with their computers. Discussions leave a trail, subject to review by other readers.

These discussion happen 'out in the open', and diverting to private conversations (that are not visible to all) is NOT in the interest of the community at large.

I could understand before, and I explained:

• the limit of a 4K display with 10 bits/color on a Thunderbolt Bus is LESS that 120 Hz. The published spec that the Mac supports is 60 Hz.

• the limit for a 4K display with 10 bits/color on DIRECT HDMI (no adapters) with proper ULTRA cable is 144 Hz. at 8 bits/color, as high as 240 Hz.

Re: “ the limit for a 4K display with 10 bits/color on DIRECT HDMI (no adapters) with proper ULTRA cable is 144 Hz. at 8 bits/color, as high as 240 Hz”

Only if the monitor has a HDMI v2.1 input. If the monitor’s HDMI input is v2.0 or earlier, it will limit things so you can’t even get 4K, 60 Hz, 10 bit per channel color, and RGB 4:4:4 encoding all at the same time.