M1 Mini + 22MD4KA + ?

[JPMLondon]

Honestly, I'm at a loss here... Normally I would say I'm fairly intelligent, but the more threads I read about M1 Macs and monitors, I realise that I'm struggling. Obviously it doesn't help that I know very little about the technical ins and outs to begin with...

So - Have a 22MD4KA (the 21.5" Ultrafine, USB-C) that I'm using with my Macbook 2015. Upgrading to an M1 Mini later this week and would like to run two screens. However, this is obviously where the problems start.

Initially thought I'd add another Ultrafine and was simply debating whether to go for the 24" or 27", but can see that'd be a no-go as the TB3 ports will only allow for one screen even if the 21.5" is "just" USB-C and the 24" could daisychain - Correct?

This means screen two needs to be HDMI as you can't adapt from the HDMI port of the Mac to the TB/USB-C port of an Ultrafine - Correct?

I really like the crispness of my current screen and the fact I can do all controls from my mac and that I don't have a sea of cables and thingiemajiggies flooding my desk. And this is where I'm getting a bit concerned, as it seems I'd quickly end up compromising on one of those as I'd have to settle for a screen that's not optimised for Mac.

So, if I were a screen guru - what would I do?

 

[Apple Knowledge Navigator]

If I recall, the 21.5" model doesn't support daisy-chaining - only the 24" and 27" inch models do. Now, there's an argument to be made that you could sell the 21.5" and get the 24" instead, but you would have to weigh up the pros and cons.

Depending on your situation, I would keep the LG 21.5" and get a cheap HDMI monitor to go beside it. You haven't said how you intend to use your Mac, but the cheaper HDMI display would be ideal for anything admin related/not graphics critical.

 

[JPMLondon]

Ah, I thought you could always daisy-chain in.

I'm not working with graphics related stuff nor do I play heavy games, but I am kinda pedantic. Let's just say that if looks less crisp than the 21.5" 4K - or Macbook native display for that matter - I'll probably cry myself to sleep every night. And nobody wants that...

I'm not that price sensitive since my primary options are around £600 and £1200 to begin with, so not looking for a bargain. Looking for something that's going to complement the 21.5" and not look off next to it. What I gather is that 4K is optimal on 21-22" and that for a 27" 5K would be better. But most 4Ks are at least 27".

But nay-naying 27" 4K is probably a bit too pedantic, no?

 

[joevt]

So - Have a 22MD4KA (the 21.5" Ultrafine, USB-C) that I'm using with my Macbook 2015. Upgrading to an M1 Mini later this week and would like to run two screens. However, this is obviously where the problems start.

To use two screens optimally, one needs to be connected to the HDMI 2.0 port and the other to a Thunderbolt port.

Initially thought I'd add another Ultrafine and was simply debating whether to go for the 24" or 27", but can see that'd be a no-go as the TB3 ports will only allow for one screen even if the 21.5" is "just" USB-C and the 24" could daisychain - Correct?

Correct.

If I recall, the 21.5" model doesn't support daisy-chaining - only the 24" and 27" inch models do. Now, there's an argument to be made that you could sell the 21.5" and get the 24" instead, but you would have to weigh up the pros and cons.

Depending on your situation, I would keep the LG 21.5" and get a cheap HDMI monitor to go beside it. You haven't said how you intend to use your Mac, but the cheaper HDMI display would be ideal for anything admin related/not graphics critical.

LG UltraFine displays use USB-C.
The 21.5" 4K (older model) supports USB-C (4K).
The 24" 4K (newer model) supports USB-C or Thunderbolt (4K).
The 27" 5K (older model) supports Thunderbolt 3 (5K).
The 27" 5K (newer model) supports USB-C (4K) or Thunderbolt (5K).

The 24" can support Daisychain when connected as Thunderbolt 3, but the M1 Macs can only support 1 display from the Thunderbolt ports so daisy chain cannot be used in this case unless you consider using a DisplayLink adapter for the second display.

The 27" 5K does not have a second Thunderbolt port for daisy chaining (because Thunderbolt usually can only supply two DisplayPort signals, and the 5K display uses both of them to support 5K60Hz 10bpc; a Thunderbolt controller has one DisplayPort output so the second Thunderbolt port must be used to supply the second DisplayPort signal - so you can't even daisychain non-display Thunderbolt devices).

This means screen two needs to be HDMI as you can't adapt from the HDMI port of the Mac to the TB/USB-C port of an Ultrafine - Correct?

I really like the crispness of my current screen and the fact I can do all controls from my mac and that I don't have a sea of cables and thingiemajiggies flooding my desk. And this is where I'm getting a bit concerned, as it seems I'd quickly end up compromising on one of those as I'd have to settle for a screen that's not optimised for Mac.

So, if I were a screen guru - what would I do?

There exist HDMI 2.0 to DisplayPort 1.2 adapters.
The following cable seems to combine a HDMI 2.0 to DisplayPort 1.2 converter (like the Club 3D CAC-1331) with a DisplayPort + USB type A to USB-C cable (like the Belkin Charge and Sync cable) so that you can use all the USB features of a USB-C display like the 21.5" or 24" LG displays.

HDMI (Output) to USB-C(Input Thunderbolt) Cable For XDR Ultrafine Mac Monitor | eBay

Support Apple Monitor，Apple XDR ， LG ultrafine and all USB-C MONITOR (ALT-DP MODE). Designed for ALL HDMI OUTPUT DEVICE to USB-C INPUT MONITOR. Design For HDMI to USB type-C One Way Only. For all other monitor only need HDMI to USB-C will get all 4k 60hz or 1080P 144hz with sound.

www.ebay.com

Be aware that HDMI 2.0 can only support 4K60Hz at 8 bpc unless chroma sub sampling is used. DisplayPort 1.2 can support 4K60Hz 10bpc without chroma sub sampling.

What I gather is that 4K is optimal on 21-22" and that for a 27" 5K would be better. But most 4Ks are at least 27".

4K 27" doesn't look bad when using the resolution that you would normally use on a 5K 27".

On my 4K 27", I use the resolution that you would normally use on a 6K 32".

 

[JPMLondon]

Thanks joevt for making it so clear and confirming my points, really appreciated...

To use two screens optimally, one needs to be connected to the HDMI 2.0 port and the other to a Thunderbolt port.

As in "better than using an adapter like the one you link to"?

Be aware that HDMI 2.0 can only support 4K60Hz at 8 bpc unless chroma sub sampling is used. DisplayPort 1.2 can support 4K60Hz 10bpc without chroma sub sampling.

According to the 22MD4KA tech specs it has "Colour depth (per channel) 8 bit". I think this is what you're referring to? Which then means it's perfectly fine and won't impact quality in this case?
(however, would if I got a 10 bit secondary screen)

4K 27" doesn't look bad when using the resolution that you would normally use on a 5K 27".

On my 4K 27", I use the resolution that you would normally use on a 6K 32".

That's also what I'd think and, while I'm pedantic, I'd probably be happy and might note be able to tell the difference between 4 and 5 in any case...

Off the top of my head I've got three good choices now:

Adapter for the 22 4K plus either the LG 27 5K or 24 4K for primary, or a HDMI 27 4K
Considering your initial comment about optimal, does that mean you would recommend the HDMI screen over the adapter?

Thanks again!

 

[joevt]

As in "better than using an adapter like the one you link to"?

Considering your initial comment about optimal, does that mean you would recommend the HDMI screen over the adapter?

The adapter I linked connects to HDMI 2.0 and uses all the bandwidth of HDMI 2.0 to connect a DisplayPort 1.2 display, so it should be just as good as connecting a HDMI 2.0 display except not sure about HDR and such - the HDMI 2.0 converter might not be the best? but you only have a DisplayPort 1.2 LG UltraFine 4K to connect there so it doesn't matter.

According to the 22MD4KA tech specs it has "Colour depth (per channel) 8 bit". I think this is what you're referring to? Which then means it's perfectly fine and won't impact quality in this case?
(however, would if I got a 10 bit secondary screen)

Oh, I forgot. The 21.5" display has a resolution of 4096x2304 which is higher than 4K (3840x2160) so it can't do 10bpc. The pixel clock is 593 MHz so HDMI 2.0 can still handle it. Have to check if the adapter can handle it. Maximum pixel clock for 10bpc is 576 MHz for DispalyPort 1.2 (less for overhead). A DisplayPort 3840x2160 display is 533 MHz while an HDMI 2.0 display is 594 MHz.

That's also what I'd think and, while I'm pedantic, I'd probably be happy and might note be able to tell the difference between 4 and 5 in any case...

You have to see them side by side to get how much nicer 5K is.

Off the top of my head I've got three good choices now:

Adapter for the 22 4K plus either the LG 27 5K or 24 4K for primary, or a HDMI 27 4K

I think you'll be happy with any of those options.

I ordered the HDMI + USB-A to USB-C adapter - I don't know if it's shipping yet. You could try the same (ships from China so might take a while) or use the adapter + cable option I mentioned instead.

 

[JPMLondon]

Oh, I forgot. The 21.5" display has a resolution of 4096x2304 which is higher than 4K (3840x2160) so it can't do 10bpc. The pixel clock is 593 MHz so HDMI 2.0 can still handle it. Have to check if the adapter can handle it. Maximum pixel clock for 10bpc is 576 MHz for DispalyPort 1.2 (less for overhead). A DisplayPort 3840x2160 display is 533 MHz while an HDMI 2.0 display is 594 MHz.

For now I'll pretend to understand all that *nodding knowingly* and hopefully actually will once I've read it a couple of times, but thanks for explaining in detail!

You have to see them side by side to get how much nicer 5K is.

I was more thinking if I could spot the difference of running the 5K screen in 5K v 4K. Have no doubt I'd see a difference between the 27 5K and the 24 4K, especially as PPIs are different. But more and more leaning towards the 27 5K by now anyway (which also comes with the aesthetic bonus of the built-in webcam).

I think you'll be happy with any of those options.

I ordered the HDMI + USB-A to USB-C adapter - I don't know if it's shipping yet. You could try the same (ships from China so might take a while) or use the adapter + cable option I mentioned instead.

Great to hear - just noticing, though, the CAC-1331 you mentioned apparently only goes to 2160 while the 22MD4K is 2304. Or would that only be when 10 bpc and still be fine with 8bpc?

 

[joevt]

Great to hear - just noticing, though, the CAC-1331 you mentioned apparently only goes to 2160 while the 22MD4K is 2304. Or would that only be when 10 bpc and still be fine with 8bpc?

For adapters, usually only the pixel clock matters. I believe the CAC-1331 should be able to output the timing required for the LG display. Same as that e-bay cable. I don't have the eBay cable yet, but I should be able to test the CAC-1331 on my Acer XV273K from my Mac mini 2018 HDMI 2.0 port by creating a matching timing using SwitchResX (I have the EDID for the 21.5" LG UltraFine 4K display which contains the timing info).

 

[Apple Knowledge Navigator]

LG UltraFine displays use USB-C.
The 21.5" 4K (older model) supports USB-C (4K).

Yes, but none of the ports provide a Thunderbolt pass-through to a secondary monitor. The one Thunderbolt port is for connecting the display to the Mac, whilst the other three USB-C ports are just that; and USB 2.0 speeds sadly.

 

[JPMLondon]

Yes, but none of the ports provide a Thunderbolt pass-through to a secondary monitor. The one Thunderbolt port is for connecting the display to the Mac, whilst the other three USB-C ports are just that; and USB 2.0 speeds sadly.

If it's the second (or in a longer chain, the last) monitor that should be fine, though. It wouldn't need a pass-through port. To dasiy-chain Ultrafines the first monitors(s) would need to be the 24" for pass-through as you note. Hence, you could chain a 24" and then a 21.5"...

However, as the M1 can't support more than one monitor from TB in any case, this unfortunately becomes a moot point.

 

[Apple Knowledge Navigator]

To dasiy-chain Ultrafines the first monitors(s) would need to be the 24" for pass-through as you note. Hence, you could chain a 24" and then a 21.5"...

I think we were at crossed wires (no pun intended!) on this one... Yes starting with a 24” is the best choice.

 

[JPMLondon]

I think we were at crossed wires (no pun intended!) on this one... Yes starting with a 24” is the best choice.

But still won't work with the M1

 

[Apple Knowledge Navigator]

But still won't work with the M1

My god this is confusing 🤦‍♂️

 

[JPMLondon]

It is. Hence my initial post. I was actually starting to find it depressing almost...

M1 TBs share two displayports, BUT can only be utilised for ONE screen (through one of the TBs). It needs two DPs to do 6K XDR for example- or a 27" 5K Ultrafine

 

[joevt]

Yes, but none of the ports provide a Thunderbolt pass-through to a secondary monitor. The one Thunderbolt port is for connecting the display to the Mac, whilst the other three USB-C ports are just that; and USB 2.0 speeds sadly.

I said the 24" supports daisychain. I did not say the 21.5" supports daisychain. I guess I should have said the 21.5" does not support daisychain.

M1 TBs share two displayports, BUT can only be utilised for ONE screen (through one of the TBs). It needs two DPs to do 6K XDR for example- or a 27" 5K Ultrafine

M1 Macs use DSC for 6K so it doesn't need two TBs in that case.
Mac GPUs that don't support DSC will use two DPs over Thunderbolt to do 6K. I don't think I've seen a PC Thunderbolt controller able to do that.
27" 5K only supports DisplayPort 1.2 connections - it uses two of them to support 5K 60Hz 10bpc.

Macbook Pro and Mini M1 Cannot output 5k resolution via Thunderbolt 3 to 2 DisplayPort Adapter

Oops. I forgot a flag: ioreg -filrw0 -k "display-timing-info" | perl -0777 ~/Downloads/ioreg.pl

forums.macrumors.com

 

[joevt]

For adapters, usually only the pixel clock matters. I believe the CAC-1331 should be able to output the timing required for the LG display. Same as that e-bay cable. I don't have the eBay cable yet, but I should be able to test the CAC-1331 on my Acer XV273K from my Mac mini 2018 HDMI 2.0 port by creating a matching timing using SwitchResX (I have the EDID for the 21.5" LG UltraFine 4K display which contains the timing info).

My Acer XV273K can accept the LG 21.5" timing for 4096x2304 which looks like this:
4096x2304@59.999Hz 142.198kHz 593.82MHz h(8 32 40 +) v(1 8 57 -) 16:9
My Mac mini 2018 can produce that from the DisplayPort outputs of the Thunderbolt ports.

I did some tests with the CAC-1331 connected to the HDMI 2.0 port of the Mac mini 2018. It does not like the timing but it can do 4096x2304 up to 53Hz. Beyond that gives DisplayPort static. At 58Hz the display disconnects. I don't know if the LG 21.5" supports refresh rate other than its normal 60Hz timing.

I tried direct from the HDMI 2.0 port without the CAC-1331 to determine if the problem could be with the DisplayPort to HDMI 2.0 converter built into the Mac mini 2018. It seems to have more problems without the adapter than with the adapter... Should probably test this with a real GPU...

 

[JPMLondon]

M1 Macs use DSC for 6K so it doesn't need two TBs in that case.
Mac GPUs that don't support DSC will use two DPs over Thunderbolt to do 6K. I don't think I've seen a PC Thunderbolt controller able to do that.
27" 5K only supports DisplayPort 1.2 connections - it uses two of them to support 5K 60Hz 10bpc.

Sorry, yes of course... It's for the 5K it needs two DPs

 

[JPMLondon]

My Acer XV273K can accept the LG 21.5" timing for 4096x2304 which looks like this:
4096x2304@59.999Hz 142.198kHz 593.82MHz h(8 32 40 +) v(1 8 57 -) 16:9
My Mac mini 2018 can produce that from the DisplayPort outputs of the Thunderbolt ports.

I did some tests with the CAC-1331 connected to the HDMI 2.0 port of the Mac mini 2018. It does not like the timing but it can do 4096x2304 up to 53Hz. Beyond that gives DisplayPort static. At 58Hz the display disconnects. I don't know if the LG 21.5" supports refresh rate other than its normal 60Hz timing.

I tried direct from the HDMI 2.0 port without the CAC-1331 to determine if the problem could be with the DisplayPort to HDMI 2.0 converter built into the Mac mini 2018. It seems to have more problems without the adapter than with the adapter... Should probably test this with a real GPU...

Thanks a lot for the testing! My brain is starting to make weird squeaky sounds...

According to LGs tech specs the 21.5" should be able to run between 48-60Hz as far as I understand it:
https://www.lg.com/us/monitors/lg-22MD4KA-B-4k-uhd-led-monitor

If I understand you correctly both the 2018 Mini and the Acer are happy about the setting, which would indicate they should perform fine and any problem would rest with the CAC-1331. However, your second test indicates there's something amiss in any case and hence the CAC might be coping just fine?

I know you haven't received it yet, but would you reckon the adapter you linked to on eBay will perform to 2304 @ 60Hz? They seem pretty confident it can handle "every 4K" as well as 5K...

 

[joevt]

Thanks a lot for the testing! My brain is starting to make weird squeaky sounds...

According to LGs tech specs the 21.5" should be able to run between 48-60Hz as far as I understand it:
https://www.lg.com/us/monitors/lg-22MD4KA-B-4k-uhd-led-monitor

If the display works as low as 48Hz then you should be able to find a timing that works for 4096x2304 with the CAC-1331 or the eBay cable (which I haven't tested yet).

If I understand you correctly both the 2018 Mini and the Acer are happy about the setting, which would indicate they should perform fine and any problem would rest with the CAC-1331. However, your second test indicates there's something amiss in any case and hence the CAC might be coping just fine?

Right. No problem with direct DisplayPort output from Mac mini 2018 or DisplayPort input to the display.
The problem could be with the CAC-1331 or the HDMI 2.0 converter in the Mac mini 2018.

I know you haven't received it yet, but would you reckon the adapter you linked to on eBay will perform to 2304 @ 60Hz? They seem pretty confident it can handle "every 4K" as well as 5K...

I can't say for sure. They don't say that it does 5K. They only say you can connect the USB for the USB audio of the display.
5120x2160 (5K 34" display) can be done through HDMI 2.0 using 51Hz but didn't work with the CAC-1331 and XV273K.

I did some more testing with the HDMI 2.0 output of a Radeon RX 580 + CAC-1331 with the XV273K for the 4096x2304 resolution using CVT-RB timings.
A timing is ok if the display stays steady for a minute:
50Hz: ok
51Hz: ok
52Hz: not steady
53Hz: ok
54Hz: blank
55Hz: not steady
56Hz: blank
57Hz: ok
58Hz: ok
59Hz: wrong color, not steady
60Hz: blank (native timing from 21.5" LG UltraFine 4K)
For CVT-RB2 timings, all were blank.

I tried 5120x1440 and 5120x2160 and 5120x2880 but the CAC-1331 doesn't like them even if the refresh rate is only 30Hz. The XV273K can handle those timings fine through DisplayPort or HDMI 2.0 from the RX 580. I suppose the Mac mini 2018 iGPU can do those resolutions also since Big Sur added support for > 4096 width timings (but HDMI 2.0 of the Mac mini 2018 may have problems like I found with 4096x2304 timings).

 

[JPMLondon]

Thanks again for all the testing!

I tried 5120x1440 and 5120x2160 and 5120x2880 but the CAC-1331 doesn't like them even if the refresh rate is only 30Hz. The XV273K can handle those timings fine through DisplayPort or HDMI 2.0 from the RX 580. I suppose the Mac mini 2018 iGPU can do those resolutions also since Big Sur added support for > 4096 width timings (but HDMI 2.0 of the Mac mini 2018 may have problems like I found with 4096x2304 timings).

Which would not be surprising as even the M1 Minis are officially supported on HDMI to only 4K and the TB to 6K...