External displays for MacBook Pro (M1) & HDMI cable version standards?

[AnakChan]

[This is more a display and HDMI standard question rather than about the MacBook Pro]
[Edit: I take that back, this does seem to be a MBP issue: I used the same short HDMI v2.0 cable on a minPC and it works fine with the display]

I've been using an external display with my MacBook Pros and whilst there's USB-C support, it seems with the Macs, I have to use the HDMI output instead of Thunderbolt/USB-C to drive the display as the display doesn't seem to work despite the display features saying it does.

Recently I bought a new (and much shorter) HDMI cable to replace the current 2m cable I'm using. However I noticed that whilst the MBP recognise there's a display, the display itself doesn't "light up". Mouse moves and scrolls over from the MBP display over to the display, but the display itself is not lit. The display is not faulty as switching back to the long HDMI cable, it lights up again.

The only thing I can think of is that the new short HDMI cable is v2.0 and I'm speculating the older 2m long HDMI cable is v1.4. Has anyone ever encountered such a thing that different HDMI cable standards could cause the display to "not display" on the external display but "lie" to MBP that it's actually functioning? Even if the external display isn't supporting HDMI v2.0 (I'm guessing on this again), wouldn't it just "signal" back to the MBP on the v2.0 cable to fall back to v1.4 protocols instead?

 

[Bigwaff]

What specific MBP model and specs?

 

[AnakChan]

I've got two (both same behaviour) MacbookPro18,1 (M1 Pro 16GB RAM) & MacbooPro18,4 (M1 Max 64GB RAM). Rather hilariously I've used the original HDMI cable that came stock with the external display and that stock HDMI cable exhibits the same behaviour as the short HDMI v2.0 cable.

The ONLY cable that works consistently is the long 2m HDMI (v1.4?) cable.

I've used all 3 cables with my miniPC (Intel based Windows 11) and they work fine with the display.

 

[Bigwaff]

Your HDMI ports are 2.0 ports supporting a single 4K display with a refresh rate of up to 60Hz. Does that match up with your cable and display specs?

 

[AnakChan]

The cables are v2.0 4K 60Hz refresh, & and the display is also 4K 60Hz refresh but don't know if they're v2.0 (or v1.4a). But again, (speculating that) even if the display isn't v2.0, wouldn't the MBP negotiate to a lower protocol irrespective of the whether the cable is V1.4a or V2.0?

FYI I've just now tried my Raspberry Pi (with the Argon40 case) and that works fine with all the cables too with the display. It's quite specifically now just both MBPs that seem to be fussy about which HDMI cables are used.

Note, I'm not too hard up about trying to make the whole thing work. I know my display is probably ancient (2-3 yrs old?), but is more a mere curiosity that HDMI cables for the MBP aren't so plug 'n play. If anything, I have a mere suspicion that something has changed with the OS upgrades as I'm pretty sure 1-2 yrs back I had the MBP working with the very same display using the display's original HDMI cable. I'm on Sonoma 14.5 on my MBPs.

 

[theluggage]

I have to use the HDMI output instead of Thunderbolt/USB-C to drive the display as the display doesn't seem to work despite the display features saying it does.

With USB-C you need to make sure that you're using a USB-C cable with USB 3.2 support and not a "charge cable" (as often supplied with phones etc.) which physically lacks the high-speed data wires needed for both USB 3.2 and DisplayPort. You can reliably tell the two types of cables apart by the fact that they look identical... er.... Safest bet is with a Thunderbolt 4-branded cable because Intel are stricter about cable markings, but cheaper "USB-C with USB 3.2 & DisplayPort" are OK.

(Currently looking an unmarked USB-C to USB-C cable which may be the one that came with my second display, or did it come with my Kindle... Grr!)

 

[AnakChan]

With USB-C you need to make sure that you're using a USB-C cable with USB 3.2 support and not a "charge cable" (as often supplied with phones etc.) which physically lacks the high-speed data wires needed for both USB 3.2 and DisplayPort. You can reliably tell the two types of cables apart by the fact that they look identical... er.... Safest bet is with a Thunderbolt 4-branded cable because Intel are stricter about cable markings, but cheaper "USB-C with USB 3.2 & DisplayPort" are OK.

(Currently looking an unmarked USB-C to USB-C cable which may be the one that came with my second display, or did it come with my Kindle... Grr!)

Cheers. Had that covered already. I even tried using Apple's thunderbolt cable - didn't work. I just blame it on the display's implementation. Unfortunately my miniPCs don't have USB-C ports for data, as such I couldn't test miniPC -> USB-C -> display.

 

[bradman83]

There’s likely something about the cable that macOS doesn’t like, an incompatible chip or something. I had a similar issue with an HDMI to USB-C adapter cable. It worked fine on my Windows work laptop but the MBP did the exact same thing - macOS recognized the display and I could move the mouse to it but it didn’t give any sort of video signal, the display was black.

Is it a name brand cable or a generic brand?

 

[AnakChan]

There’s likely something about the cable that macOS doesn’t like, an incompatible chip or something. I had a similar issue with an HDMI to USB-C adapter cable. It worked fine on my Windows work laptop but the MBP did the exact same thing - macOS recognized the display and I could move the mouse to it but it didn’t give any sort of video signal, the display was black.

Is it a name brand cable or a generic brand?

Two cables - the HDMI cable that came with the display, and a recently purchased from Amazon. I'd say both are generic. The 2m HDMI cable that does work is also generic.

No worries, I guess HDMI cables aren't as plug 'n play as I thought it'd be for Apple. Furthermore I'm probably due to get a better display for the Mac anyway. I'll just keep this display for non-Mac miniPCs or my Raspberry Pis.

 

[theluggage]

No worries, I guess HDMI cables aren't as plug 'n play as I thought it'd be for Apple. Furthermore I'm probably due to get a better display for the Mac anyway. I'll just keep this display for non-Mac miniPCs or my Raspberry Pis.

Problem is, every TV, computer display and cable manufacturer tests their own stuff with Windows PCs, while the Raspberry Pi is based on a fairly generic Broadcomm set top box SoC... Testing stuff with Mac is kinda all down to Apple. Hard to say if Apple are doing it wrong or if everybody else is expecting Windows' and popular set top boxes' foibles...

 

[HDFan]

recently purchased from Amazon.

The cable isn't certified. I would return it. You want a certified cable which has the certification label on the packaging. There are variations but it should look something like this:

 

[Alameda]

The cable isn't certified. I would return it. You want a certified cable which has the certification label on the packaging. There are variations but it should look something like this:

View attachment 2395370

THIS
Licensed, tested HDMI cables are not allowed to list the HDMI version number. There is no such thing as an HDMI 2.0 or HDMI 2.1 cable.

So if the cable lists the version number, it’s probably uncertified and unlicensed. Don’t buy it.

An HDMI High Speed Certified cable supports 4K60 8-bit 4:4:4
An HDMI Premium High Speed Certified Cable also supports 4K60 8-bit 4:4:4
An HDMI Ultra High Speed Certified Cable supports 4K120, 8K60 and even 8K120.

 

[AnakChan]

The cable isn't certified. I would return it. You want a certified cable which has the certification label on the packaging. There are variations but it should look something like this:

View attachment 2395370

Wow! Thx Didn't know about this. Thank you!