MBP M3 vs M4 to Studio Display

PMurphy wrote:

Easiest way to show what I mean... here are the M3Pro options (3200x1800 is one) and then the M4Plain options

That's very odd.

In Retina scaling modes, the internal drawing canvas has twice as many pixels in each direction as the nominal Displays Settings ("UI looks like") resolution. For Retina "looks like 3200x1800" mode, the internal canvas has 6400x3600 pixels – it has a higher resolution than the native resolution of a 32" Apple 6K Pro Display XDR.

Thus if you were attaching two monitors to a M3 MacBook Air (which has a resolution limit of 6K on the always-available output, and of 5K on the "lid closed" one), Retina "like 3200x1800" mode would not be available on the "lid closed monitor." There is at least one report from a M3 MacBook Air user, on these forums, for which this is the most logical explanation.

In your case, the display specifications of the M3 Pro MBPs and the plain M4 MBP are virtually the same. Note the key "up to 6K resolution" phrase in both sets of Technical Specifications.

Which versions of macOS are you running on the M3 Pro MBP and on the plain M4 MBP? Is it possible that this is a macOS thing, with Apple having moved the 3200x1800 option to the "Show all resolutions" list – or maybe even having removed it altogether?

MacBook Pro (14-inch, M3 Pro or M3 Max, Nov 2023) - Technical Specifications - Apple Support

MacBook Pro (16-inch, Nov 2023) - Tech Specs - Apple Support

M3 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, 2024) - Tech Specs - Apple Support

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

you can still select mirror displays and close the lid. Can you be certain that is NOT your setting?

you can have a 'shipped in the box' cable that does not have the ThunderBolt trademark on it, and that would make it a candidate for substitution.

FYI, I'm using a 4K monitor on a M1 Max Studio running Ventura. The connection is a USB-C to USB-C one. My machine's specifications say that it can drive up to four 6K monitors over USB-C and one 4K display over HDMI.

If I show resolutions as icons, Ventura offers me four Retina choices (1920x1080, 2560x1440, 3008x1692, and 3360x1890) plus native 3840x2160. If I show the resolutions as a list, several more choices appear – including Retina 3200x1800 mode, even with "Show all resolutions" turned off. I can select the 3200x1800 mode, and it works just fine (other than the size/readability of the text).

Seems to me like your plain M4 MBP should also be able to support Retina "like 3200x1800" mode on any "up to 6K" output.

PMurphy wrote:

I am wondering if you can only get this resolution on Pro or Max level processors?

If so, Apple needs to do a better job of documenting that.

I could be mistaken, but I believe that every Apple Silicon Mac – going back to the very first, lowest-end, plain M1 models – has featured the ability to drive one external USB-C / Thunderbolt Display with a resolution of up to 6K, at 60 Hz. Even those Macs for which one external display was the limit.

Based on that, I would expect all of them to be able to support Retina "like 3200x1800" mode on a 27" Apple 5K Studio Display if it was the only display.

I think that at the very highest resolutions over ThunderBolt, the Mac may use TWO connections through one ThunderBolt cable to get high-end results. I blundered on this on the Wikipedia article on ThunderBolt:

The Apple Pro Display XDR, which macOS allows to connect using two HBR3 connections to a Mac, doesn't support Display Stream Compression (DSC). That would be 51.84 Gbit/s, impossible for Thunderbolt 3, but it works because the two 3008×3384 10bpc 60 Hz 648.91 MHz signals of the XDR display only require 38.9 Gbit/s total and Thunderbolt does not transmit the DisplayPort stuffing symbols used to fill the HBR3 bandwidth.

PMurphy wrote:

So I was in an Apple Store yesterday and did confirm if the chip is M4 Pro or higher, that resolution is available . M4 Plain does not offer that resolution.

Looks like Apple's Technical Specifications don't always capture the finer details of what Retina scaling options may, or may not, be available.

AFAIK, all Apple Silicon Macs can drive a single 6K display over Thunderbolt. The reference is presumably to an Apple Pro Display XDR, with a native resolution of 6016 by 3384 pixels. If you run that in an exact Retina scaling mode of "looks like 3018 by 1692 pixels", the internal drawing canvas has 6016 by 3384 pixels.

But many Macs can draw on larger canvases. Mine (M1 Max Mac Studio) offers "like 3360x1890" as a choice for my 4K display, even though that implies a 6720 by 3780 canvas.

So I wonder what the rules are for which Macs / chips are willing to support Retina modes with "outsized" drawing canvases.

what cable is in use in each case?

what version of macOS is in use in each case?

what other differences can you identify?

are any additional displays also being used?

Which chip is in use in each case?

M3 - plain, Pro, or Max?

M4 - plain, Pro, or Max?

is that the original shipped in the box 1 meter Apple cable? is it clearly marked with the ThunderBolt trademark on each end?

Lid closed?

¿Have you checked to be absolutely certain you have NOT enabled "Mirror displays"?