MacBook Pro 2017 doesn't recognize Thunderbolt USB-C display

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Level 1

11 points

MacBook Pro 2017 doesn't recognize Thunderbolt USB-C display

Hi, I'm writing here for an issue with my old but good MacBook Pro 13" with Touch Bar (4 Thunderbolt 3 ports). I recently bought a new OLED 4K Display (PA32UCDM) and I want to connect it to my Mac with its Thunderbolt USB-C cable.

The cable in the case and the port on the monitor is Thunderbolt 4, but the standard it's backward compatible with Thunderbolt 3 (sure?). When I connect in EVERY port on my MBP, simply the Mac doesn't even recognize it, the battery isn't charing (monitor's port have a 95 W output so well above for my MBP)... the Mac only "sense" the USB peripheral connected to the integrated USB hub on the monitor.

I tried monitor and cable with my iPhone 15 Pro Max and iPad Pro 11" M1 and they work flawlessly; the issue is ONLY on my Mac; also I tried different DisplayPort settings on the monitor (1.2 vs 1.4 vs 1.4 + USB 3.2), but nothing; I also have done a reset of SMC and PRAM without solving anything.

Can someone help me?

[Re-Titled by Moderator]

MacBook Pro 13″, macOS 13.7

Posted on Sep 4, 2025 10:37 AM

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Answer 1

Sep 4, 2025 11:26 AM in response to Teo_D

I’d suspect this is because your Mac doesn’t support Thunderbolt 4.

Thunderbolt is backwards compatible, and cross compatible, but is not forward compatible; it doesn’t add Thunderbolt features that it doesn’t already have.

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Answer 2

Teo_D Author

Level 1

11 points

Sep 4, 2025 12:00 PM in response to MrHoffman

Thanks for the quick reply!

My MBP doesn't support Thunderbolt 4, but the display does, as does the cable... but if it's backwards compatible, shouldn't it still work, "limiting" itself to Thunderbolt 3 functionality (e.g. lower bandwidth, resolution I don't know...)? It's really strange that USB devices work through that cable, but the Mac won't charge or output video/audio...

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Answer 3

Teo_D Author

Level 1

11 points

Sep 4, 2025 12:20 PM in response to Teo_D

Little update: searching in Console some hours ago... I don't know if this can be useful.

2025-09-04 16:34:39.975378+0200: LinkUpdate: 3.0 event: Insert [0]

2025-09-04 16:34:39.975856+0200: NOTICE: Addr: 3.0 event: Insert [0] source: 0

2025-09-04 16:34:39.982964+0200: NOTICE: doFallback addr 3

2025-09-04 16:34:40.074454+0200: NOTICE: Looking for: AUS 6b3:3207

2025-09-04 16:34:40.077568+0200: NOTICE: Bit rate: 0x0

2025-09-04 16:34:40.077629+0200: NOTICE: IsDVI bandwidth 3840x2160 - 4000x2222, 24 bpp [533280000 Hz, 1599840000 Mbs] [max: 2@HBR2, 2160 Mbs] @ 8 bpc

2025-09-04 16:34:40.083276+0200: NOTICE: Populated addr 3.0 6b3:3207 UUID 1010101 order 0:0 tx 2:2 dsp 4 WL 0 MS 0 edid 256 undef 0 DSC 0

2025-09-04 16:34:40.635683+0200: NOTICE: Do online device addr 3.0 processCount 1

2025-09-04 16:34:40.667730+0200: NOTICE: Sync LinkTrain Port: 3: SST, 2 lanes @ HBR2 FEC disabled TPS 3

2025-09-04 16:34:40.776779+0200: NOTICE: kAGDCFBOverrideTimingRange on FB [2] dscMaxBpp 0 maxBandwidth 8590 Mbps

2025-09-04 16:34:40.777295+0200: NOTICE: FB AGDC state FB[2] - ON

2025-09-04 16:34:40.821745+0200: NOTICE: inject FB[2] change

2025-09-04 16:34:40.838629+0200: NOTICE: Do online device addr 3.0 id 6b3:3207 UUID 1010101 order 0:0 edid 256 undef 0 - completed

2025-09-04 16:34:41.142907+0200: NOTICE: kIOFBNotifyOnlineChange 0x1 fb[ 2 ] -> online, Thu Sep 4 16:34:46 2025

2025-09-04 16:34:41.143009+0200: NOTICE: Update display map to fb[ 2 ] - online

2025-09-04 16:34:48.715250+0200: LinkUpdate: 3.0 event: Remove [1]

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Answer 4

Sep 4, 2025 01:01 PM in response to Teo_D

Your Mac lacks Thunderbolt 4, and your monitor requires it.

Cables and Thunderbolt adapters don’t magically create Thunderbolt 4 features in the other end of the connection.

Sure, Thunderbolt 4 is compatible with features of earlier Thunderbolt, and newer Thunderbolt computers can often connect with older Thunderbolt devices using adapters, but earlier Thunderbolt computers do not have the newer features of Thunderbolt 4 just because some newer Thunderbolt 4 device is connected.

Your Thunderbolt 4 display doesn’t make your Thunderbolt 3 Mac capable of sending Thunderbolt 4. Same as connecting a Thunderbolt 5 device doesn’t automatically upgrade your Mac Thunderbolt 5 features, either.

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Answer 5

BobHarris

Level 9

56,477 points

Sep 4, 2025 09:01 PM in response to Teo_D

My understanding of Thunderbolt 4 is that it is the same as Thunderbolt 3, except where 3 allowed venders to cheat and not support all features, Thunderbolt 4 REQUIRED all the features to be supported, which are the full Thunderbolt 3 features.

I also understood that Apple implemented all the Thunderbolt 3 features, so it should be able to talk to Thunderbolt 4 devices.

But then again, there are always edge cases.

Does the display work with HDMI?

Are you using a Thunderbolt cable that came with the display?

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Answer 6

Teo_D Author

Level 1

11 points

Sep 5, 2025 08:12 AM in response to BobHarris

Hi Bob, firstly thank you for your time trying to help me.

About Thunderbolt 4 vs 3 I also know almost the same things... so that's a mystery.

Yes, the display works flawlessly with HDMI (connected via a Lenovo hub with SD cards, Ethernet, HDMI, etc.) and also directly with Thunderbolt with my iPhone and iPad.

And for the last question yes, I'm using the Active 40 Gbps Thunderbolt 4 cable that came with the monitor.

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Answer 7

Sep 5, 2025 12:47 PM in response to Teo_D

The supposition that Thunderbolt 4 didn’t add anything to Thunderbolt 3 is common, but is incorrect.

Thunderbolt 4 added DisplayPort 1.4 (which was either optional or was not present in early Thunderbolt 3 specs, and DP1.4 was added in some later Thunderbolt 3 implementations, and this Mac predates the DP1.4 addition — baseline Thunderbolt 3 was DP1.2), and Thunderbolt 4 added DisplayPort 1.4a and added DisplayPort 2.0, and Thunderbolt 4 added USB4 and all its giblets, and Thunderbolt 4 added at least one 100W USB PD power delivery port.

You might be able to get this monitor to work here by selecting its available DisplayPort 1.2 mode maybe, if that’s not enabled by default. That’s assuming this monitor doesn’t actually need Thunderbolt 4 (a requirement as is listed in the specs). See the user guide.

https://dlcdnets.asus.com/pub/ASUS/LCD%20Monitors/PA32UCDM/PA32UCDM_UG_English.pdf?model=PA32UCDM

But as the Asus monitor spec states the Thunderbolt host needs to be Thunderbolt 4, your Mac does not support that.

Apple doesn’t have a great list (or any list?) of which gear uses which Thunderbolt and which DisplayPort either, which is unfortunate.

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Answer 8

Teo_D Author

Level 1

11 points

Sep 7, 2025 06:50 AM in response to MrHoffman

Probably you centered the issue from the beginning... is the limitation at Thunderbolt 3 of the MBP.

The Apple Support, after a long and (surprisingly detailed) chat, advised me to try a passive shorter cable because sometimes the chip inside the cable can do strange things with oldest Thunderbolt 3 chips (like that inside my MBP). This things has been also reported online from some users, so my hope was that the issue was only to to the cable.

So I tried to bought two cable, one passive and certified for Thunderbolt 4 in Apple Store and one passive with Thunderbolt 3 certification in an online marketplace; the first one, together with the Asus' active cable, has been tested with my Mac connected to a Studio Display in the Apple Store and they both worked flawlessly.

Unfortunately, at home the TB3 and TB4 cable both didn't work except, like before, the "USB part" of the connection. So I'm throwing in the towel...

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Answer 9

Sep 7, 2025 08:15 AM in response to Teo_D

that PA32UCDM display appears to be a 3840x2160 (4K) display with 10 bits/color HDR

interfaces include

2x ThunderBolt 4 - (be certain you have plugged the computer cable into the correct ThunderBolt jack, the one with a computer symbol under it)

1x HDMI 2.1, but your computer does not support that, and it can not be derived using adapters.:

USB-C limited to 10 G bits/sec (and does not appear to support video input)

it also appears you MUST use On-screen Display settings to select HDMI OR ThunderBolt Input, unless Auto-Detect is selected

as MrHoffman alluded to, there do appear to be On-Screen Display settings for different DisplayPort versions, and as he said, you should select DisplayPort 1.2 for use with Thunderbolt-3 computer output:

DisplayPort Stream: Compatibility with graphic card. Select

DisplayPort 1.2, DisplayPort 1.4 or DisplayPort 1.4 + USB

3.2 by graphic card DP version.

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Answer 10

Sep 7, 2025 11:59 PM in response to Teo_D

OWC Rocket Yard Blog - The Simple Guide to Thunderbolt Forwards and Backwards Compatibility

"Can Thunderbolt 4 devices be used with Thunderbolt 1, Thunderbolt 2, and Thunderbolt 3 host devices?

Thunderbolt 4 provides the same maximum performance and display support as Thunderbolt 3. However, Thunderbolt 4 devices require a Mac or PC with a USB-C Thunderbolt port. That means that it’s possible to use Thunderbolt 4 devices with host devices that have Thunderbolt 3 ports, but using them with host devices that have Thunderbolt 1 and Thunderbolt 2 ports—even with an adapter—isn’t possible."

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Answer 11

Sep 8, 2025 09:31 AM in response to Servant of Cats

Servant of Cats wrote:

Thunderbolt 4 provides the same maximum performance and display support as Thunderbolt 3.

Same display support? No, it doesn’t. T3 started with DP1.2, and T3 finished with DP1.4. T4 has DP 2.0. Etc. See my reply above

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Answer 12

Sep 8, 2025 09:33 PM in response to MrHoffman

MrHoffman wrote:

Servant of Cats wrote:

Thunderbolt 4 provides the same maximum performance and display support as Thunderbolt 3.

Please note that this is what Other World Computing wrote in their Rocket Yard blog.

Same display support? No, it doesn’t. T3 started with DP1.2, and T3 finished with DP1.4. T4 has DP 2.0. Etc. See my reply above

Maybe someone ought to leave a comment to that effect on the Rocket Yard article.

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