How many external displays can an M4 or M4 pro support?

M3 (plain) like the 13-in and 15-in supports up to ONE External fully hardware-accelerated external display.

Except the M3 MacBook Air models with 13 or 15-in display, (and certain M3 plain MacBook Pro models when running 14.6 or later) which can support a second external display instead of the built-in display when you close the cover on the built-in display. This may require MacOS 14.6 or later.

M4 (plain) supports up to Two fully hardware-accelerated external displays (three for Mac mini)

M4 PRO processor supports up to Two fully hardware-accelerated external displays. (three for Mac mini)

M4 MAX processor supports up to Four fully hardware-accelerated external displays.

M4 ULTRA processor supports up to Eight fully hardware-accelerated external displays

Tech Specs now available here:

MacBook Pro - Tech Specs - Apple

MacBook Pro - Tech Specs - Apple

John_Shin wrote:

Thanks for the detailed answer.

But I want to know more clearly.

Mackbook M4 products are not displayed and sold in Apple stores in Korea yet.

Macbook M4, M4 Pro, M4 MAX All M4 series Macbooks can see three monitors without closing the lib, i.e., the Macbook M4 itself and two external monitors.

The Technical Specifications for all of these MacBooks are available on the main Apple site.

MacBook Pro - Apple

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

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

MacBook Pro (16-inch, 2024) - Tech Specs - Apple Support

The specifications don't go into the finer details of how the resolution limits affect what Retina scaling modes are available, but they do appear to address the question of how many monitors you can have.

The statement is mostly correct but contains some ambiguities or requires clarification. Below is an analysis of each part:

1. "M3 (plain) like the 13-in and 15-in supports up to ONE External fully hardware-accelerated external display."

• ✅ Correct:
  • The M3 (plain) chip in MacBook Air (13-inch and 15-inch) and entry-level MacBook Pro models supports only one external display. This aligns with Apple's specifications for "plain" M-series chips (M1, M2, M3).

2. "Except the M3 MacBook Air models with 13 or 15-in display, (and certain M3 plain MacBook Pro models when running 14.6 or later) which can support a second external display instead of the built-in display when you close the cover on the built-in display. This may require MacOS 14.6 or later."

• 🔄 Partially Correct:
  • Closing the laptop lid to use clamshell mode disables the internal display, allowing a second external monitor to function in place of the built-in display.
• However, the mention of "certain M3 plain MacBook Pro models" is unclear and possibly incorrect:
  • • For MacBook Air models with plain M3 chips, clamshell mode may allow a second external monitor, but this behavior depends on macOS features, not the hardware itself.
• It's not confirmed that macOS 14.6 or later is specifically required for this behavior—clamshell mode has been a standard macOS feature for years.

3. "M4 (plain) supports up to Two fully hardware-accelerated external displays (three for Mac mini)."

• ✅ Correct:
  • M4 (plain) in MacBook Pro supports two external displays while still running the internal display.
  • M4 (plain) in Mac mini supports three external displays, consistent with its higher display output capabilities compared to laptops.

4. "M4 PRO processor supports up to Two fully hardware-accelerated external displays. (three for Mac mini)"

• ✅ Correct:
  • M4 Pro supports up to two external displays on laptops and three external displays on Mac mini, consistent with previous Pro-tier M-series chips.

5. "M4 MAX processor supports up to Four fully hardware-accelerated external displays."

• ✅ Correct:
  • M4 Max supports up to four external displays, consistent with its positioning as a higher-end chip with superior display capabilities.

Summary of Corrections and Notes:

• The statement about clamshell mode on M3 MacBook Air and certain M3 plain MacBook Pro models (with macOS 14.6 or later) needs clarification:
  • Clamshell mode is not specific to macOS 14.6 or M3 models; it has been a general feature of macOS laptops for a long time.
  • It's unlikely that "certain M3 plain MacBook Pro models" behave differently—plain M3 chips all support only one external display unless clamshell mode is used.
• Everything else is accurate and aligns with the capabilities of the M3 and M4 series chips.

Key Takeaways:

1. MacBook Pro (M4) vs. Mac mini (M4):

• • Both support 8K at 60Hz or 4K at 240Hz for a single display.
  • The MacBook Pro (M4) supports up to two external monitors, while the Mac mini (M4) supports up to three external monitors.

1. Pro and Max Chips:

• • The M4 Pro in both MacBook Pro and Mac mini supports up to 2 or 3 displays, respectively.
  • The M4 Max MacBook Pro offers unmatched flexibility, supporting up to 4 external displays.

The statement contains some inaccuracies and speculative elements. Here's a breakdown of what is incorrect and correct:

1. "The additional display that came in with M4 plain was possible because memory bandwidth and basic memory speed was modestly increased in the M4, and now there was enough bandwidth so that a second external display could be supported."

• 🔄 Partially Correct but Misleading:
• Correct:
  • • The M4 chip does indeed support two external displays, whereas previous "plain" M-series chips (M1, M2, M3) supported only one.
• Improvements in memory bandwidth and speed in the M4 could contribute to this increased capability.
• Incorrect:
  • • The ability to drive multiple displays is not solely or primarily about memory bandwidth. It is more directly tied to the graphics subsystem architecture, specifically the inclusion of additional display controllers and rasterizer units in the M4.
• The bandwidth improvements in the M4 might help overall system performance but are not the definitive reason for the second display capability.

2. "Apple decided that since the Could do it, they Would do it, and added the Rasterizer/DisplayGenerator for another display."

• 🔄 Partially Correct but Speculative:
• Correct:
  • • Apple likely added a second display controller (responsible for rendering and outputting display signals) to the M4 chip, enabling the support for a second external display.
• This kind of hardware addition (e.g., more rasterizers and display generators) is common in chip evolution to meet user needs.
• Incorrect:
  • The claim "since they could do it, they would do it" is speculative and lacks technical backing. Apple's decisions are typically driven by balancing hardware capabilities, software optimization, and market needs rather than a simple "we can, so we will" approach.

Corrected Statement:

The M4 chip supports an additional external display compared to earlier "plain" M-series chips, primarily due to the inclusion of an extra display controller in the graphics subsystem. While modest improvements in memory bandwidth and speed in the M4 may enhance overall performance, the key enabler for the second display is the upgraded graphics architecture, which includes additional rasterizers and display generators. This architectural enhancement allows the M4 to handle the extra display workload effectively.

Summary of Key Points:

• Memory bandwidth is a minor factor; the graphics subsystem's upgrades (e.g., additional display controllers) are the main reason for the second display capability.

the additional display that came in with M4 plain was possible because memory bandwidth and basic memory speed was modestly increased in the M4, and now there was enough bandwidth so that a second external display could be supported.

Apple decided that since the Could do it, they Would do it, and added the Rasterizer/DisplayGenerator for another display.

Note that while MacBook Pros with plain M4 chips and M4 Pro chips can support two external displays at the same time as the internal one, there is no guarantee that they will provide power to run portable monitors.

Your monitors might need their own power supplies (wall adapters or portable rechargeable power banks).

M3 MacBook Airs support one external display with the lid open, two with it closed.

M3 MacBook Pros with plain M3 chips originally only supported one external display, period. The hardware was there to support a second “lid closed” display, as on the M3 MacBook Airs - but macOS code to use that feature was not present, so Apple didn’t advertise the capability. Later, a macOS update added the missing code to enable this feature on M3 MacBook Pros with plain M3 chips. When that update came out, Apple revised the Technical Specifications for those machines (but made no mention in the new Technical Specifications that the feature had ever been absent -saving that detail for a Support article).

That is why, for M3 MacBook Pros with plain M3 chips, the version of macOS they are runnIng matters,

Display support mostly depends on the chip.

Plain M4 chips and M4 Pro chips can support up to three displays, where any built-in display counts against that total. Closing the lid of a Mac notebook with a plain M4 chip or a M4 Pro chip does not free up a display output - so on such Macs, there is always a limit of at most two external displays.

Low-end 24” M4 iMacs are an exception to the rule. They only support one external display, even though the specifications of all other Macs with plain M4 chips would suggest that the chip could support two.

Although the plain M4 and the M4 Pro both support up to three displays, there are slight differences in Technical Specifications that favor the M4 Pro in some circumstances.

Mac notebooks with plain M3 chips are, as far as I know, the only Apple Silicon Macs with built- in displays which can take the video output used to support that display, and switch it to a “lid closed” monitor to increase the maximum number of external displays supported in “clamshell mode.”. But plain M3 chips still have a limit of two active displays. The change in the plain M4 chips to support three displays total (including any built-in one) is a more convenient solution.

To my amazing apple community friends:

I never deal with or look at forums, but I had to just share my MAC thoughts here. I got the M2 (24GB) MacBook Air. I so, just, always will, love these mac units. I found out can not do multiple monitors on this M2 unit, however, some folks saying fancy expensive USB-C docking stations allow a software driver extension to multiple monitors. I just purchased a 49" monitor to make me happy until I can get what I want. So there's the topic I wanted to share. Wow, the one I want is expensive. I've been PC guy for ever, and I'm so old, I was around when first PC and Mac were available to the public.

I've had mac's from time to time, but these M units are amazing. Wish they had the graphics power of the a fancy $2k Nvidia card, but I'm sure they will do their best to catch up. I often go to the mac sight, look up what I want it it hits almost $5k. I paid a bit for my M2 air, but I'm a saving up for the almost $5k (M4 max) unit, and I'm going to enjoy it so much, should be soon that I can get.

Just saying, everyone, go get that M4 pro/max units and enjoy multiple monitors. I'll post again when I get my M4 unit and another 49 monitor. I'lll start with M4 max unit, with 2 49's monitors. Thanks apple for these amazing units. I have a very expensive gaming PC w/4090 gpu that just sits close and not used. Funny. To ($%^$) with that PC... Ha!