PSA: For Thunderbolt 3 over distance; use *OPTICAL Thunderbolt 1/2 cables!*

Discussion in 'Mac Accessories' started by jimthing, Mar 28, 2018.

  1. jimthing, Mar 28, 2018
    Last edited: Mar 28, 2018

    jimthing macrumors 65816

    jimthing

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    #1
    Just a quick public service announcement, for the pro/advanced user Mac user community on MacRumors...

    It looks very likely that you can use the previous generation Thunderbolt 1/2 optical cables (5.5/10/30/60 metre lengths) to connect over distances longer than 2 metres!

    And most importantly, it looks like the older TB1/2 optical cable connection can meet the best speed your external storage device can offer, just as fast as using the standard copper Tbolt 3 <2m cables!

    The problem to be solved is that, at the moment, there simply aren't any optical cable solutions for Thunderbolt 3 (with the new USB-C ports), unlike the previous Thunderbolt 1 & 2 generations (using Mini DisplayPort). So users who want to keep TB3 devices away from their desks/work stations are not currently served by a native cable.
    _________
    However, in my basic testing...

    I have a couple of the LG 5K displays that connect via TB3 to the host Mac. The other day I tried to connect one of them to my 2016 15" MBPtb via a Corning TB1/2 10m optical cable I had available.
    This was achieved by using Apple TB1/2<>TB3 adapters on each end of the Corning optical cable.

    In my testing, it worked flawlessly, allowing connection to not just the display, but also the basic peripherals I had connected to the vanilla 5Gb/s USB-C ports on the back. The only thing it didn't do was power the MBP, as optical cables obviously don't carry power, unlike their shorter copper counterparts which do.

    AFAICT, this means that if you have fast (self-powered) external TB3 storage devices, you should be able to run them at a distance longer than the 2m offered by copper TB3 cables. So you don't have to put-up with the often loud noise such mass storage devices make – a top bugbear for most users.


    I'm not sure if anyone happens to have had any real-life Tbolt 3 external storage test experience with this; I don't own any fast Tbolt 3 external storage, RAID or otherwise, to test myself unfortunately. So please, if anyone can confirm if they've had any speed differences between a copper 40Gb/s Tbolt 3 cable versus the optical connection above, please do let the community know. :)


    PS. If you want to buy an optical Thunderbolt 1/2 cable, you'll have to find them from third party stores. Apple used to sell the Corning branded ones in their online stores, but currently don't. :-/
     
  2. jimthing, Mar 28, 2018
    Last edited: Mar 29, 2018

    jimthing thread starter macrumors 65816

    jimthing

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    #2
    ...oh well, I guess no one around here notices these issues.

    Never mind, I'll leave it here in case someone in the near future wants fast(er) connections away from their machine, without having to resort to paying £700 for the Sonnet TB3-to-10Gb/s adapter (non iMac Pro users) – which is slower, but can do distances.
     
  3. Kier-XF macrumors member

    Kier-XF

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    #3
    FWIW, I'd love to be able to move my Thunderbolt kit further away from me, but I'm using the full bandwidth of TB3 and I would certainly see a performance hit if I used TB2 optical cables.

    My hope is that now Intel has essentially opened up the Thunderbolt spec, we might see some more reasonably-priced products coming to market... but given how long it has been since Intel did that, I'm not holding my breath - which is a real pity.
     
  4. apple_iBoy macrumors 6502a

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    #4
    How long do you think is reasonable to give people a chance to reply? Two threads and the same deal both times.
     
  5. Hans7D, May 3, 2018
    Last edited: May 10, 2018

    Hans7D macrumors newbie

    Hans7D

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    #5
    Edit: deleted and posted somewhere else. I got no reactions here.
     
  6. jeabraham macrumors newbie

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    #6
    Where is this “somewhere else”?
     
  7. Detnator macrumors regular

    Detnator

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    #7
    It's my understanding that TB2 can drive the LG TB3 5K display through the TB2 - TB3 adapter. Almost every Apple Store I've been in seem to have that display attached to a 2013 (TB2-only) Mac Pro through that adapter.

    The catch is... it only works at 4K.

    Yes, you can set it to higher resolutions, just as you can any 4K display. When you set a 4K display to something higher than 4K it approximates the resolution but it's still only physically displaying 4K worth of pixels, so you get a higher resolution with only 4K worth of fidelity.

    In this case, it's hardware scaling down the 5K physical pixels to 4K before it then approximates the higher resolution, but still with only 4K worth of fidelity, so it's not as crisp as true 5K.

    I expect that's what you're experiencing.

    Unfortunate, because I found this thread because I'm looking for TB3 cables significantly longer than 2m, which presumably have to be optical as was the case with TB1/2, but they just don't seem to exist (yet?).

    Sigh.
     
  8. jimthing thread starter macrumors 65816

    jimthing

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    #8
    That's not correct. I attached my 5K displays to a 15" MBP 2016, and they work at *full* resolution with the Apple adapters on each end.

    What you're talking about, is connecting to older machines that cannot handle 5K, hence why the 5K's drop down to 4K resolution on the Apple adapters.
     
  9. Detnator macrumors regular

    Detnator

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    #9
    Hmmm....

    Except the reason they can't handle 5K is because Thunderbolt 2 can't handle 5K. That's official.

    How can you be sure that your 5K display is displaying full 5K resolution with the two TB2 adapters?
     
  10. jimthing thread starter macrumors 65816

    jimthing

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    #10
    System Information.
     
  11. Detnator macrumors regular

    Detnator

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    #11
    Could you post a screen shot of that please? I'm still convinced this isn't accurate, but definitely open to be proven wrong. And it would be great if this is actually true.

    Also, even if System information says the display is 5K, I'm still not convinced that means it's actually displaying 5K.

    Sorry, not trying to be argumentative, but none of this makes sense. Thunderbolt 2 just doesn't have the bandwidth or the official support to handle 5K. It just doesn't. So I just don't see how this is possible.
     
  12. jimthing thread starter macrumors 65816

    jimthing

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    #12
    Sorry, but can't as cable is in use elsewhere.

    This is an optical cable, so doesn't follow the same standards as copper versions.
     
  13. Detnator macrumors regular

    Detnator

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    #13
    That's fair enough, but no matter how awesome the Thunderbolt 3 cable is, the Thunderbolt 2 adapter should still be a 20Gb/s bottleneck.

    So I guess to clarify my previous statement...

    "Sorry, not trying to be argumentative, but none of this makes sense. The Thunderbolt 2 adapter just doesn't have the bandwidth or the official support to handle 5K (no matter what else is in the chain). It just doesn't. So I just don't see how this is possible."
     
  14. vanc macrumors 6502

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    #14
  15. Senior-Switchmonkey macrumors newbie

    Senior-Switchmonkey

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    #15
    So, this thread died without confirmation of 5K over optical??
     
  16. Detnator macrumors regular

    Detnator

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    #16
    Well no... it died with confirmation of no 5K over a chain where any part of it is anything less than TB3. The OP posted about having TB2 in the chain and 5K is not supported over that.

    I'm not aware of any TB3 optical cables (where the heck are they??) so we can say with confidence that until there is optical TB3 cables, and since there's no 5K over optical anything else, then yeah, there's no 5K over optical for now at least.
     
  17. jimthing, Jan 28, 2019
    Last edited: Jan 28, 2019

    jimthing thread starter macrumors 65816

    jimthing

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    #17
    No, it says pre-2016 machines get 4K using the adapter, not later machines.
    --- Post Merged, Jan 28, 2019 ---
    No, as I said before, that's incorrect.

    My curiosity was driving me mad, so I just re-tested. As a I confirmed in my opening post, it DOES do 5K over the optical TB3 connection using two TB3 adapters on each end!

    See screen shots of before and after below, plus image of the cable with both adapters on, as proof I actually own them!

    NOTES:
    1) On the "after" pic, notice the display's serial# appears when using the optical connection.
    2) I have redacted my full name on both pics, and the full serial# on the "after" pic (for obvious reasons!).
    3) If you notice, both have exactly the same "Resolution: 2560 x 1440", as are being pixel-doubled from their full native resolution of 5120 x 2880.
    4) The "Color LCD" is the built-in display on my maxed-out 2016 15MBPtb, as all three displays are in use (MBP + LG 5K + LG 5K).
    5) It's hot-swappable: I unplugged the copper cable and did the optical one, all without rebooting.


    BEFORE (using the included active 2m LG-supplied TB3 cable):
    Screen Shot 2019-01-28 at 13.21.49.png
    AFTER (using an optical 10m TB1/2 Corning cable, with two Apple TB3<>TB1/2 adapters):
    Screen Shot 2019-01-28 at 13.26.32.png
    Pic of my optical TB1/2 cable + 2x Apple adapters:
    IMG_4033.JPG


    So now you know! Thanks.
     
  18. jimthing, Jan 28, 2019
    Last edited: Jan 28, 2019

    jimthing thread starter macrumors 65816

    jimthing

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    #18
    As I also said in my original post, re. fast connection to storage:
    I don't actually know what device you could buy/borrow to test that the speeds this optical+adapters cable set-up can achieve would be higher than 20Gbit offered by TBolt 2? Presumably you'd need a drive that can achieve over ~2GBytes/sec throughput or something?
     
  19. Detnator, Jan 28, 2019
    Last edited: Jan 28, 2019

    Detnator macrumors regular

    Detnator

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    #19
    1. Your results are inconsistent. Why does your internal display show the full resolution (2880x1800 Retina) but the LG displays only show the half resolution (2560x1440)? My iMac Pro says "5120x2880 Retina" in that line. According to your results, both those displays (or their connection) are only capable of 1440p. So you've got something else weird going on there.

    2. TB2 simply cannot support the bandwidth required for 5K. It can't.
     
  20. jimthing, Jan 28, 2019
    Last edited: Jan 28, 2019

    jimthing thread starter macrumors 65816

    jimthing

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    #20
    Because the "Default for display" resolution on the internal MBP's display, is set at setting 4 of 5, while the LG's defaults to 3 of 5. Additionally, externally connected displays show without the pixel-doubled display ppi (2560x1440) rather than the actual ppi (5120x2880), while internally connected ones show the actual ppi. Strange but true.

    How can my results possibly be described as 'inconsistent', given the evidence I've clearly presented? It can and does support 5K.

    For starters, my right LG 5K was still connected via 2m copper, while the left LG 5K was connected via the 10m optical; yet they both say exactly the same thing (except for the optical one showing the LG 5K's serial#).

    ___________
    In related news, Apple announced on their release that the new 2018 iPad Pro's can support connection to a 5K display over it's non-TB3 vanilla USB-C gen.2 (10Gbps) connection.
    https://talk.tidbits.com/t/what-happened-to-5k-displays/6638/17?u=jimthing


    ...the caveat being there are zero non-TB3 5K3K displays released, and so no one actually knows what Apple specifically means – i.e. Does it mean full 5K resolution or just 4K? Does it do this 4K or 5K resolution at full 60Hz or just 30Hz?
     
  21. jimthing thread starter macrumors 65816

    jimthing

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    #21
    Another interesting thing to note, is that using the Corning optical cable connection enables the rotation function. As you can see in the second screenshot of System Prefs, the first LG 5K shows "Rotation: Supported".

    Which tallies with this previous forum thread, where other non-LG supplied copper cables have shown to often offer the same thing:

    "LG Ultrafine (5K) users will want to see this thread"

    https://forums.macrumors.com/threads/lg-ultrafine-5k-users-will-want-to-see-this-thread.2119639
     

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