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Apple's Pro Display XDR takes Thunderbolt 3 to its limit

231 points by WithinReason 3y ago

dataworm 3y ago
The display still supports USB 3 even without DSC, because all USB data gets sent over PCIe in Thunderbolt 3. The USB controller in the Titan Ridge doesn't downgrade the ports to USB 2.0, but because 1.8 Gbps is much lower than the USB 3 bandwidth, Apple says it doesn't support USB 3 on models without DSC.
lispm 3y ago
Does the MacBook Air with M1 (or M2) actually support 10bpc on the 6k Display? It is never mentioned in the specs about the Macbook Air, AFAIK. My guess is that it does not. The M1 from 2020 also did only support 8bpc on the internal display. For the MacBook Pro with M1 Pro it is explicitly mentioned in the tech specs that it supports 6k with 10bpc. This page claims that even the M1 MacBook Air from 2020 supports 10bpc on the external 6k monitor: https://support.apple.com/en-us/HT210437 https://support.apple.com/en-us/HT210437 But the actual technical spec page for the machine never says it, AFAICS. https://support.apple.com/kb/SP825?locale=en_US https://support.apple.com/kb/SP825?locale=en_US > Simultaneously supports full native resolution on the built-in display at millions of colors and: One external display with up to 6K resolution at 60Hz My impression was that Apple implemented Thunderbolt themselves (and got rid of external chips) and that at least the first generation M1 machines lacked the 10bpc feature in the GPU and/or the Thunderbolt part.
- dmitshur 3y ago
  Do you have ideas for how to test it and find out definitively in person? I haven't found a way to confirm one way or another. The Graphics/Displays page in System Information unfortunately says nothing about colors, only resolution (https://github.com/shurcooL/home/assets/1924134/af4b19a3-b859-472b-a9ce-80d59e4f01e1 https://github.com/shurcooL/home/assets/1924134/af4b19a3-b85...). When looking at a 16-bit PNG of a white to black gradient, I'm not able to visually spot any banding even when zooming in. It's fairly easy to spot steps when looking at a 8-bit PNG version of the same gradient. But the same happens on the built-in display despite it supposedly having only 8-bit color ("support for millions of colors").
  - lispm 3y ago
    Yeah, that's definitely my experience, too. It is difficult to actually get color depth information. Several other Macs, especially the older ones tell you there the color depth. You might want to try out SwitchResX and see what it says about the screen. In some menu, there is color depth information about the screen. But I don't know if it is actually accurate and where the application gets this info from. https://www.madrau.com https://www.madrau.com
chx 3y ago
It doesn't work like that, the 40gbps is actual bus bandwidth AFAIK. https://www.thunderbolttechnology.net/sites/default/files/Thunderbolt3_TechBrief_FINAL.pdf https://www.thunderbolttechnology.net/sites/default/files/Th... figure 7 says 5120 x 2880 @ 60Hz which requires 22.18gbit/s leaves 18gbps data bandwidth. (This figure is quite important because this is one of the two only "official" sources which admits the raw data transfer limit of TB3 is 22gbps, the other is Dell at https://www.dell.com/support/kbdoc/en-uk/000149848/thunderbolt-3-usb-c-maximum-data-transfer-rate-on-dell-systems https://www.dell.com/support/kbdoc/en-uk/000149848/thunderbo... otherwise you'll only see the 40gbps speed.) What happens rather is much simpler, the blog post forgot to set the calculator to 10 bit https://linustechtips.com/topic/729232-guide-to-display-cables-adapters-v2/?section=calc&H=6016&V=3384&F=60&bpc=10&calculations=show&formulas=show https://linustechtips.com/topic/729232-guide-to-display-cabl... if they did you'd see the data rate required is 38.20gbit/s so the bus is near full. USB C has separate 2.0 wires so unless you have DP 1.4 for DSC you can only use those for USB data, there's no space for anything else.
- korhojoa 3y ago
  That's not really the full story, when this is about displays. I currently have a display that requires Displayport 2.1 to get everything out of it, and with DSC and DP 1.4, I can get a "theoretical bitrate" that is higher than what they would normally allow. (Of course, this doesn't change what the link can do, it just allows you to do more with the same bandwidth) On thunderbolt 3 systems, the link is on HBR3, which with DSC allows 120hz, 10bit at 7680x2160. No DSC support limits the refresh to 60hz and 8bit (as then you won't have the higher rates available anyway, since DSC is mandatory with newer standards). You can check https://tomverbeure.github.io/video_timings_calculator https://tomverbeure.github.io/video_timings_calculator to see what is possible.
- brigade 3y ago
  Thunderbolt 3 doesn't use those USB 2.0 wires; that was one of the big changes in USB4/TB4 to use them. Once you're in Thunderbolt 3 mode, all USB ports are provided by PCIe xHCI controllers by the TB3 device. In actuality, the mode where the XDR display consumes 38gbps of uncompressed display bandwidth is an Apple-only mode requiring special Titan Ridge firmware that aggregates 6 lanes of HBR3. Contrary to the article, Alpine Ridge does not support 6k, which specifically is why the iMac Pro doesn't support 6k output. It requiring special firmware is also why this mode only works when directly connected to the Mac. But yeah, it's annoying that everyone throws bandwidth numbers around without mentioning or even thinking if it's link rate or data rate.
amluto 3y ago
Is Thunderbolt 3 like the rest of the USB-C protocols in that dedicated pins are used for USB2? If so, the bandwidth doesn't need to add up -- the cable carries the Thunderbolt protocol and USB2 separately.
- Moto7451 3y ago
  https://www.etechnophiles.com/thunderbolt-pinout-1-2-3-4/ https://www.etechnophiles.com/thunderbolt-pinout-1-2-3-4/ Based on the D+/- pairs I believe you’re correct. On Titan Ridge and later add in cards USB 2 is expected to be passed through via a motherboard header as the controllers lack a dedicated USB 2 chip.
- Reason077 3y ago
  With Thunderbolt the USB controller is built in to the display, with full bandwidth available to each USB port. But if the dedicated USB2 pins were being used, it would just be acting as a USB hub, and the total bandwidth on all ports would be limited to 480 Mbps?
- ray519 3y ago
  No. TB3 still stuck with only using PCIe-USB3 controllers over tunneled PCIe. The other replies are right on the host side, where newer TB3 controllers pass-through USB2 from the chipset. But that is only used for non-TB connection modes. Same with TB3 Titan Ridge Docks. They are wired to the USB2 pins, because in legacy mode (DP Alt mode + USB3) the USB2 will be physically on those pins together with the 2 high speed wire pairs used for USB3. Only USB4 started using those USB2 wires on USB4 connections.
mark_l_watson 3y ago
I have one of these. My Dad died last August (just before his 102 birthday) and he had bought himself a Pro Display XDR about 6 months before that. My brother is a PC person and I am a Mac person so I got the Pro Display. It is an amazing display and I love it, but I would never buy one for myself. It is obviously fine for programming, but for me it really stands out as something for consuming entertainment, even though I only get 4K content. It is capable of, I think, 7K with the right computer and has 10 bit color depth. When my Dad first bought it, I used it to play Apple Arcade games on my iPad Pro - that was fairly spectacular. EDIT: my Dad had a Black Magic video camera that I think had 8K resolution, and so he had a lot of fun with his setup.
- Spooky23 3y ago
  I'm sorry for your loss, but I have to say that your post made me smile. How awesome that you and your brother got to enjoy dad at 101 being able to nerd out with video and high end displays.
  - mark_l_watson 3y ago
    Thanks!
- Teever 3y ago
  Wow it would have been neat to talk to the kind 102 year old person who is buying this kind of hardware. I'd love to know what he thought about the progress of technology and how he felt it had impacted society.
- dbspin 3y ago
  Your 101 year old father was out shooting on an Ursa 12K? What a guy.
  - xattt 3y ago
    The frail elderly are a very prominent group in society because their needs are so great. Robust “old-old” adults tend to blend in because they are inconspicuous and they go on about their business. I think we’re going to see a “silver tsunami” of robust elderly persons as millennials and Gen Xers age simply because healthy lifestyle activities that had been a part of their lives. I.e. don’t buy into Acorn Stairlift and Lifealert futures.
tedunangst 3y ago
Would people be happy if Apple refused to support incremental improvements? Sorry, the sticker says Thunderbolt 3, you can't use fast USB devices here. You have to wait for the next product cycle to get a new sticker.
xoa 3y ago
I still desperately wish the industry had been able to push through to an optical data + plain power interconnect standard ages ago instead of it falling apart. It's so pleasant to deal with fiber. The same OS2 or OM3 I installed over a decade ago for 10 Gbps is still fine for 40 or 100 Gbps. Cost was a complaint at one point, yet even without the enormous economies of scale a general standard would bring price and performance lines have ended up converging anyway. 40G SR (so still good to 150m) modules are now at $40 or less, even 100G is less than $100. Putting that onto simpler fiber instead of MTP/MPO with SFP56 remains much more expensive, a 50G-SR is still like $280, but that appears to primarily be a product of it being very new and not yet scaled, not that it couldn't have been years ago. And that still then runs to 100m with duplex LC. Meanwhile, Apple wants $70 a pop for a single, 1m Thunderbolt 4 cable, and that's only been increasing. What will Thunderbolt 5 be? Corning and I think one other briefly did optical Thunderbolt cables, but those were $500-1000. Whereas premade quality duplex OM4 with helical steel armor runs more like $2.20/meter. Feels like we somehow ended up in a yet another technology path dependent evolution path where decisions that saved a bit at the time have then imposed major costs forever more :(. Man it'd be so cool to just be able to run a screen and input boxes hundreds of feet away from a workstation for $60, or have an $8-12 cable be good for decades of evolution in bandwidth barring regular wear (and when it's that cheap who cares even if it breaks after 5 years?), or be able to route displays/TVs and PCIe and whatever else around like any other networking with no compromises. Sigh.
- BiteCode_dev 3y ago
  Fiber doesn't bend well, which for a cable that will be moved regularly by ordinary customers, is game over.
  - kllrnohj 3y ago
    It bends just fine. There's tons of fiber cables for "ordinary users" including HDMI, DisplayPort, Thunderbolt, VR link cables, and, of course, toslink. You just end up with the extra cost and complexity of having transceivers built into the cable which is a waste especially at these speeds where copper is clearly a limitation.
mmastrac 3y ago
Normally I find Fabien's articles to be a lot clearer, but I came away from this one not understanding what it was really talking about. Does the monitor have XDR? Does it auto-negotiate extra bandwidth on newer MacBooks?
- BearOso 3y ago
  XDR means nothing. It's an Apple buzzword. With DSC, you have at the minimum a fixed amount of bandwidth gain because blanking intervals can always be compressed, and DP is packetized without strict timing limitations. That should be enough to guarantee the additional bandwidth.
Reason077 3y ago
From the article: > "But why is the 16-inch MacBook Pro able to run USB 3.1 (10Gbps)?" USB 3.1 Gen 1 is 5 Gbps, not 10 Gbps. (My Thunderbolt LG Ultrafine 4K also has USB 3.1 Gen 1 ports on it, so I should know...)
- jeroenhd 3y ago
  I think they mean USB 3.2 Gen 2x1, which does support 10Gbps throughput. Apple's tech support page about their Thunderbolt 4 cable (https://support.apple.com/en-om/HT210997 https://support.apple.com/en-om/HT210997) also states "USB 3.1 Gen 2 data-transfer speeds up to 10Gbps". I'm a little confused by Apple's machines wouldn't support USB 3.2 Gen 2x2 when they support USB 4 and Thunderbolt. I guess they couldn't figure out how to get faster USB out of their chipset? They list the same limitation on their iMac USB 3 ports (https://support.apple.com/guide/imac/take-a-tour-imac-apd2e7352054/mac https://support.apple.com/guide/imac/take-a-tour-imac-apd2e7...).
  - Reason077 3y ago
    > "I think they mean USB 3.2 Gen 2x1, which does support 10Gbps throughput." They explicitly say USB 3.1 Gen 1 in the article, and the linked technical document [1] > "I'm a little confused by Apple's machines wouldn't support USB 3.2 Gen 2x2 when they support USB 4 and Thunderbolt." Yeah, it's weird, but Apple has never supported Gen 2x2, AFAIK. 2x2 means you have two 10 Gbps channels running in parallel on two sets of pins, but USB 4 does a similar thing to get 40 Gbps and they do support that. Shrug. [1] https://fabiensanglard.net/xdr/Pro_Display_White_Paper_Feb_2020.pdf https://fabiensanglard.net/xdr/Pro_Display_White_Paper_Feb_2...
londons_explore 3y ago
Can we please stop having displays be 'special'. I should be able to plug hundreds of displays into my laptop with any combination of USB hubs and have them all just work. Displays shouldn't need allocated bandwidth - they should give the best display quality possible given the available bandwidth. Nothing moving on the display - no bandwidth used. Just a little animated gif? Just a few kilobits used. Full screen HD video? Gigabits used. Gigabits not available? Frame rate and/or quality drop. This is the exact behaviour of plugging in hundreds of USB ethernet adaptors. Why should displays be different?
- andrewmcwatters 3y ago
  The real reason? Because display protocols don't work that way. If they did, it would require that your displays retained state more than they do today.
  - tverbeure 3y ago
    FWIW: pretty much all displays have one or two screen buffers today... You need at least one to enable overdrive. And you need a second one for low frame rate compensation.
- NavinF 3y ago
  Besides the dynamic bandwidth allocation, you pretty much described how USB 4 and all versions of Thunderbolt works. Personally I'd hate to see my display bandwidth drop when I copy files to a flash drive so I'm glad no monitors support that part of your suggestion. Input lag = horrible UX.
  - rbanffy 3y ago
    > I'd hate to see my display bandwidth drop when I copy files to a flash drive Well… if you connect the flash drive to the monitor and not the computer that should be expected. OTOH, I’d love to have faster data rates when my monitor image doesn’t change much (such as when I’m writing code or letting the computer move lots of data between external drives.
fleventynine 3y ago
> Let's remove 20% due to 8b/10 encoding Thunderbolt 3 uses 64b/66b encoding (unlike display port 1.2 alt mode), so there's more bandwidth left over for non-display protocols.
- dishsoap 3y ago
  came here to comment this
- fabiensanglard 3y ago
  Thank you for pointing out this mistake. So the 40 Gbps value advertised by Intel is not the pre-encoding rate but post-encoding rate. This means TB3 pre-encoding rate is 40.25gbps. Minus encoding we get post-encoding = 40Gbps (before TB headers). This leads me to question my USB maths. E.g.: USB 3.2 Gen 1×1 advertised as 5,000 Mbps, but is that pre-encoding or post-encoding? Is it `5000 Gbps pre-encoding -> 8b/10b > 4000 Gbps` or `6250 Gbps pre-encoding -> 8b/10b > 5000 Gbps` Same question for USB 3.2 Gen 2×1 which uses 128b/132b (I double checked this time :P!).
  - _kb 3y ago
    USB 3.2 gen 1x1 is a 5Gbps data rate. With the 8b/10b coding that provides 500MB/s throughput. USB 3.2 gen 2x1 runs at 10Gbps. After the 128b/132b coding this provides 1212MB/s.
  - Kirby64 3y ago
    USB-IF defines their data rates in terms of link rate. So 5 Gbps after 8b10b encoding is 4 Gbps. Makes sense, since fastest transfers never exceed 500 MB/s over USB3. Same applies for the 128b/132b variant, except it's only a ~3% speed reduction, so it's much harder to see that in practical testing.
rnantes 3y ago
Excited to upgrade to a Mac with Thunderbolt 5 which should allow for 6K at 120Hz with 10 bit color over a single cable. All this with an OLED panel is just about peak display for me.(though miniLED would be fine too)
- peebeebee 3y ago
  Add a nice integrated iPhone quality webcam, and I think it would be endgame display. If there is one company that could do this, it would be Apple. Although I have an LG Ergo 4k 32inch at home and I think the 16:9 ratio is just not enough for having 2 windows side by side. You'd only get 1500pixels per window on retina 6K. I would've liked it to be a bit wider. Or maybe I'd go for a smaller 27 inch, and put my laptop screen as a secondary screen next to it.
tambourine_man 3y ago
That Al Gore setup is really awesome, specially for 2007.
- mistersquid 3y ago
  > That Al Gore setup is really awesome, specially for 2007. Yeah, the OP links to an image of Al Gore in front of 3 displays with the caption Climate central Gore in his Nashville home office. where he wrote his new book. Mind map software and huge Post-it notes help him order his thoughts [0] I did some medium-searching but couldn't come up with a name for the mind mapping software Gore used. Also interesting is how the 3 displays present in aesthetically pleasing way because they are identical (resolution, size, bezels, etc). [0] https://fabiensanglard.net/xdr/al.webp https://fabiensanglard.net/xdr/al.webp
  - tambourine_man 3y ago
    Those are the 30” Apple Cinema Displays, if I’m not mistaken. I dreamed of having one of them. 3 is just preposterous
    - kalleboo 3y ago
      When I was in Uni I got a remote side gig developing some software. I spent my whole first paycheck on a 30" Cinema Display, replacing a rig of 3 hand-me-down CRTs. Never regretted it for a second, that thing was pure luxury.
  - NikkiA 3y ago
    > I did some medium-searching but couldn't come up with a name for the mind mapping software Gore used. Purely a guess, but probably OmniGraffle back then.
gatkinso 3y ago
I have one, its amazing obviously but the backlighting is not 100% perfect. Looking forward to the next one of course. I even got it to work with my PC via a [Belkin VR cable](https://www.belkin.com/support-article/?articleNum=316883 https://www.belkin.com/support-article/?articleNum=316883). Even has USB support.
knodi 3y ago
I'm really waiting on a new version of XDR to get one.
huy-nguyen 3y ago
The article states the wrong resolution for the Apple display and it’s an interesting mistake because these days there are actually 2 versions of 6K in consumer-marketed computer monitors: the one used by the Apple display (6016x3384) and the slightly larger one used by the Dell U3224KB 6K that came out earlier this year (6144 x 3456). In fact, an interesting thing people found out when they use the Dell 6K display on Intel MacBook Pros running Mac OS between 10.15 and 13.6 is that the Mac cannot do Display Stream Compression at the Dell's native 6144 x 3456, hence the Mac can only drive the monitor at 30hz instead of 60hz. However, if they can fool the Mac into thinking the display is 6016x3384 (same as the Apple display), DSC magically works and they get 60hz on the Dell (at the expense of sacrificing some screen real estate). Apple must probably hardcode the 6016x3384 resolution somewhere in their OS code. Thankfully people report that this problem has been fixed as of Mac OS 14.1 but that bug existed for 4 years. Edit: this problem only seems to happen on Intel, not Apple silicon machines.
- sinfulprogeny 3y ago
  > that the Mac cannot do Display Stream Compression at the Dell's native 6144 x 3456, Can't, or won't? M1 MacBook pros for some reason can't do 4k120 over hdmi unless you buy a specific usbc-hdmi adapter and fool it into thinking it's displayport (or something like that, I'm paraphrasing. You can find info if you search for cablematters DDC 4k120 m1.)
  - wtallis 3y ago
    There's no "fool it into thinking it's displayport". What you're describing is having the Mac actually literally emit a DisplayPort signal, and a separate device converting that to an HDMI signal. The USB-C HDMI Alt mode standard was never implemented by any real products, and all USB-C to HDMI converters are active adapters that consume DisplayPort signals and emit HDMI signals. Not all of those support HDMI 2.1, which introduced a drastically different signalling mode for HDMI in order to support much higher data rates (and also added display stream compression, further increasing the maximum resolution and refresh rate capabilities).
pram 3y ago
It’s not the thunderbolt controller totally, the Vega and GCN (RX580 etc) Radeon cards on older Macs don’t support DSC. The 16 inch MBP had RDNA cards (which do) For example the Vega MPX cards on the Mac Pro don’t do it, but the 5700 etc cards will give you the added port bandwidth.
bastard_op 3y ago
Apple's got nothing left to offer here, Thunderbolt died with their relation to intel. It's a corpse still running.
bastard_op 3y ago
You wanted really 4k over that? Silly human.
bastard_op 3y ago
So I test this theory daily, I run 2/3 full 4k desktops, 30/60hz when I can get it, but it's a desktop under linux. Kde is ass, so is gnome, not much deals with the hz. I would like one day a desktop that works under linux, I'm trying gnome from kde currently, still a mess.
jiggawatts 3y ago
One thing I'm jealous of as a Windows user is that HDR "just works" in the Apple ecosystem. I was just watching a YouTube video describing how to edit HDR videos in DaVinci Resolve, and step #1 was basically: "Get a Mac". There is simply no monitor equivalent to the Apple Pro Display XDR available from any other vendor, short of the ludicrously expensive Sony mastering monitors that are made to order. There are no 4K OLED HDR monitors that can hit 1,000 nits, for example. Meanwhile my local electronics store has an entire row of TVs with that spec! There are 6K and 8K monitors... but they don't do HDR, or do it so badly that it's actually making things worse. Even if there was proper HDR display for PCs, or if I simply forked over $5K for the Apple XDR monitor... it wouldn't work. Not in practice, not for video editing or for photography. There's something fundamentally broken with the entire Windows and Linux ecosystems that it has been a decade of widespread HDR support everywhere else, but in the PC world it's just crickets chirping and wolves howling in the distance.
cardiffspaceman 3y ago
Does this support HDCP? At what maximum distance will it support an encrypted connection?
- NavinF 3y ago
  Why not use a HDCP stripper (often marketed as a port splitter) and an optical cable? That'll solve both of your problems

231 points by WithinReason 3y ago

The display still supports USB 3 even without DSC, because all USB data gets sent over PCIe in Thunderbolt 3. The USB controller in the Titan Ridge doesn't downgrade the ports to USB 2.0, but because 1.8 Gbps is much lower than the USB 3 bandwidth, Apple says it doesn't support USB 3 on models without DSC.

lispm 3y ago

Does the MacBook Air with M1 (or M2) actually support 10bpc on the 6k Display? It is never mentioned in the specs about the Macbook Air, AFAIK. My guess is that it does not. The M1 from 2020 also did only support 8bpc on the internal display. For the MacBook Pro with M1 Pro it is explicitly mentioned in the tech specs that it supports 6k with 10bpc. This page claims that even the M1 MacBook Air from 2020 supports 10bpc on the external 6k monitor: https://support.apple.com/en-us/HT210437 https://support.apple.com/en-us/HT210437 But the actual technical spec page for the machine never says it, AFAICS. https://support.apple.com/kb/SP825?locale=en_US https://support.apple.com/kb/SP825?locale=en_US > Simultaneously supports full native resolution on the built-in display at millions of colors and: One external display with up to 6K resolution at 60Hz My impression was that Apple implemented Thunderbolt themselves (and got rid of external chips) and that at least the first generation M1 machines lacked the 10bpc feature in the GPU and/or the Thunderbolt part.

dmitshur 3y ago
Do you have ideas for how to test it and find out definitively in person? I haven't found a way to confirm one way or another. The Graphics/Displays page in System Information unfortunately says nothing about colors, only resolution (https://github.com/shurcooL/home/assets/1924134/af4b19a3-b859-472b-a9ce-80d59e4f01e1 https://github.com/shurcooL/home/assets/1924134/af4b19a3-b85...). When looking at a 16-bit PNG of a white to black gradient, I'm not able to visually spot any banding even when zooming in. It's fairly easy to spot steps when looking at a 8-bit PNG version of the same gradient. But the same happens on the built-in display despite it supposedly having only 8-bit color ("support for millions of colors").
- lispm 3y ago
  Yeah, that's definitely my experience, too. It is difficult to actually get color depth information. Several other Macs, especially the older ones tell you there the color depth. You might want to try out SwitchResX and see what it says about the screen. In some menu, there is color depth information about the screen. But I don't know if it is actually accurate and where the application gets this info from. https://www.madrau.com https://www.madrau.com

chx 3y ago

It doesn't work like that, the 40gbps is actual bus bandwidth AFAIK. https://www.thunderbolttechnology.net/sites/default/files/Thunderbolt3_TechBrief_FINAL.pdf https://www.thunderbolttechnology.net/sites/default/files/Th... figure 7 says 5120 x 2880 @ 60Hz which requires 22.18gbit/s leaves 18gbps data bandwidth. (This figure is quite important because this is one of the two only "official" sources which admits the raw data transfer limit of TB3 is 22gbps, the other is Dell at https://www.dell.com/support/kbdoc/en-uk/000149848/thunderbolt-3-usb-c-maximum-data-transfer-rate-on-dell-systems https://www.dell.com/support/kbdoc/en-uk/000149848/thunderbo... otherwise you'll only see the 40gbps speed.) What happens rather is much simpler, the blog post forgot to set the calculator to 10 bit https://linustechtips.com/topic/729232-guide-to-display-cables-adapters-v2/?section=calc&H=6016&V=3384&F=60&bpc=10&calculations=show&formulas=show https://linustechtips.com/topic/729232-guide-to-display-cabl... if they did you'd see the data rate required is 38.20gbit/s so the bus is near full. USB C has separate 2.0 wires so unless you have DP 1.4 for DSC you can only use those for USB data, there's no space for anything else.

korhojoa 3y ago
That's not really the full story, when this is about displays. I currently have a display that requires Displayport 2.1 to get everything out of it, and with DSC and DP 1.4, I can get a "theoretical bitrate" that is higher than what they would normally allow. (Of course, this doesn't change what the link can do, it just allows you to do more with the same bandwidth) On thunderbolt 3 systems, the link is on HBR3, which with DSC allows 120hz, 10bit at 7680x2160. No DSC support limits the refresh to 60hz and 8bit (as then you won't have the higher rates available anyway, since DSC is mandatory with newer standards). You can check https://tomverbeure.github.io/video_timings_calculator https://tomverbeure.github.io/video_timings_calculator to see what is possible.
brigade 3y ago
Thunderbolt 3 doesn't use those USB 2.0 wires; that was one of the big changes in USB4/TB4 to use them. Once you're in Thunderbolt 3 mode, all USB ports are provided by PCIe xHCI controllers by the TB3 device. In actuality, the mode where the XDR display consumes 38gbps of uncompressed display bandwidth is an Apple-only mode requiring special Titan Ridge firmware that aggregates 6 lanes of HBR3. Contrary to the article, Alpine Ridge does not support 6k, which specifically is why the iMac Pro doesn't support 6k output. It requiring special firmware is also why this mode only works when directly connected to the Mac. But yeah, it's annoying that everyone throws bandwidth numbers around without mentioning or even thinking if it's link rate or data rate.

amluto 3y ago

Is Thunderbolt 3 like the rest of the USB-C protocols in that dedicated pins are used for USB2? If so, the bandwidth doesn't need to add up -- the cable carries the Thunderbolt protocol and USB2 separately.

Moto7451 3y ago
https://www.etechnophiles.com/thunderbolt-pinout-1-2-3-4/ https://www.etechnophiles.com/thunderbolt-pinout-1-2-3-4/ Based on the D+/- pairs I believe you’re correct. On Titan Ridge and later add in cards USB 2 is expected to be passed through via a motherboard header as the controllers lack a dedicated USB 2 chip.
Reason077 3y ago
With Thunderbolt the USB controller is built in to the display, with full bandwidth available to each USB port. But if the dedicated USB2 pins were being used, it would just be acting as a USB hub, and the total bandwidth on all ports would be limited to 480 Mbps?
ray519 3y ago
No. TB3 still stuck with only using PCIe-USB3 controllers over tunneled PCIe. The other replies are right on the host side, where newer TB3 controllers pass-through USB2 from the chipset. But that is only used for non-TB connection modes. Same with TB3 Titan Ridge Docks. They are wired to the USB2 pins, because in legacy mode (DP Alt mode + USB3) the USB2 will be physically on those pins together with the 2 high speed wire pairs used for USB3. Only USB4 started using those USB2 wires on USB4 connections.

mark_l_watson 3y ago

I have one of these. My Dad died last August (just before his 102 birthday) and he had bought himself a Pro Display XDR about 6 months before that. My brother is a PC person and I am a Mac person so I got the Pro Display. It is an amazing display and I love it, but I would never buy one for myself. It is obviously fine for programming, but for me it really stands out as something for consuming entertainment, even though I only get 4K content. It is capable of, I think, 7K with the right computer and has 10 bit color depth. When my Dad first bought it, I used it to play Apple Arcade games on my iPad Pro - that was fairly spectacular. EDIT: my Dad had a Black Magic video camera that I think had 8K resolution, and so he had a lot of fun with his setup.

Spooky23 3y ago
I'm sorry for your loss, but I have to say that your post made me smile. How awesome that you and your brother got to enjoy dad at 101 being able to nerd out with video and high end displays.
- mark_l_watson 3y ago
  Thanks!
Teever 3y ago
Wow it would have been neat to talk to the kind 102 year old person who is buying this kind of hardware. I'd love to know what he thought about the progress of technology and how he felt it had impacted society.
dbspin 3y ago
Your 101 year old father was out shooting on an Ursa 12K? What a guy.
- xattt 3y ago
  The frail elderly are a very prominent group in society because their needs are so great. Robust “old-old” adults tend to blend in because they are inconspicuous and they go on about their business. I think we’re going to see a “silver tsunami” of robust elderly persons as millennials and Gen Xers age simply because healthy lifestyle activities that had been a part of their lives. I.e. don’t buy into Acorn Stairlift and Lifealert futures.

tedunangst 3y ago

Would people be happy if Apple refused to support incremental improvements? Sorry, the sticker says Thunderbolt 3, you can't use fast USB devices here. You have to wait for the next product cycle to get a new sticker.

xoa 3y ago

I still desperately wish the industry had been able to push through to an optical data + plain power interconnect standard ages ago instead of it falling apart. It's so pleasant to deal with fiber. The same OS2 or OM3 I installed over a decade ago for 10 Gbps is still fine for 40 or 100 Gbps. Cost was a complaint at one point, yet even without the enormous economies of scale a general standard would bring price and performance lines have ended up converging anyway. 40G SR (so still good to 150m) modules are now at $40 or less, even 100G is less than $100. Putting that onto simpler fiber instead of MTP/MPO with SFP56 remains much more expensive, a 50G-SR is still like $280, but that appears to primarily be a product of it being very new and not yet scaled, not that it couldn't have been years ago. And that still then runs to 100m with duplex LC. Meanwhile, Apple wants $70 a pop for a single, 1m Thunderbolt 4 cable, and that's only been increasing. What will Thunderbolt 5 be? Corning and I think one other briefly did optical Thunderbolt cables, but those were $500-1000. Whereas premade quality duplex OM4 with helical steel armor runs more like $2.20/meter. Feels like we somehow ended up in a yet another technology path dependent evolution path where decisions that saved a bit at the time have then imposed major costs forever more :(. Man it'd be so cool to just be able to run a screen and input boxes hundreds of feet away from a workstation for $60, or have an $8-12 cable be good for decades of evolution in bandwidth barring regular wear (and when it's that cheap who cares even if it breaks after 5 years?), or be able to route displays/TVs and PCIe and whatever else around like any other networking with no compromises. Sigh.

BiteCode_dev 3y ago
Fiber doesn't bend well, which for a cable that will be moved regularly by ordinary customers, is game over.
- kllrnohj 3y ago
  It bends just fine. There's tons of fiber cables for "ordinary users" including HDMI, DisplayPort, Thunderbolt, VR link cables, and, of course, toslink. You just end up with the extra cost and complexity of having transceivers built into the cable which is a waste especially at these speeds where copper is clearly a limitation.

mmastrac 3y ago

Normally I find Fabien's articles to be a lot clearer, but I came away from this one not understanding what it was really talking about. Does the monitor have XDR? Does it auto-negotiate extra bandwidth on newer MacBooks?

BearOso 3y ago
XDR means nothing. It's an Apple buzzword. With DSC, you have at the minimum a fixed amount of bandwidth gain because blanking intervals can always be compressed, and DP is packetized without strict timing limitations. That should be enough to guarantee the additional bandwidth.

Reason077 3y ago

From the article: > "But why is the 16-inch MacBook Pro able to run USB 3.1 (10Gbps)?" USB 3.1 Gen 1 is 5 Gbps, not 10 Gbps. (My Thunderbolt LG Ultrafine 4K also has USB 3.1 Gen 1 ports on it, so I should know...)

jeroenhd 3y ago
I think they mean USB 3.2 Gen 2x1, which does support 10Gbps throughput. Apple's tech support page about their Thunderbolt 4 cable (https://support.apple.com/en-om/HT210997 https://support.apple.com/en-om/HT210997) also states "USB 3.1 Gen 2 data-transfer speeds up to 10Gbps". I'm a little confused by Apple's machines wouldn't support USB 3.2 Gen 2x2 when they support USB 4 and Thunderbolt. I guess they couldn't figure out how to get faster USB out of their chipset? They list the same limitation on their iMac USB 3 ports (https://support.apple.com/guide/imac/take-a-tour-imac-apd2e7352054/mac https://support.apple.com/guide/imac/take-a-tour-imac-apd2e7...).
- Reason077 3y ago
  > "I think they mean USB 3.2 Gen 2x1, which does support 10Gbps throughput." They explicitly say USB 3.1 Gen 1 in the article, and the linked technical document [1] > "I'm a little confused by Apple's machines wouldn't support USB 3.2 Gen 2x2 when they support USB 4 and Thunderbolt." Yeah, it's weird, but Apple has never supported Gen 2x2, AFAIK. 2x2 means you have two 10 Gbps channels running in parallel on two sets of pins, but USB 4 does a similar thing to get 40 Gbps and they do support that. Shrug. [1] https://fabiensanglard.net/xdr/Pro_Display_White_Paper_Feb_2020.pdf https://fabiensanglard.net/xdr/Pro_Display_White_Paper_Feb_2...

londons_explore 3y ago

Can we please stop having displays be 'special'. I should be able to plug hundreds of displays into my laptop with any combination of USB hubs and have them all just work. Displays shouldn't need allocated bandwidth - they should give the best display quality possible given the available bandwidth. Nothing moving on the display - no bandwidth used. Just a little animated gif? Just a few kilobits used. Full screen HD video? Gigabits used. Gigabits not available? Frame rate and/or quality drop. This is the exact behaviour of plugging in hundreds of USB ethernet adaptors. Why should displays be different?

andrewmcwatters 3y ago
The real reason? Because display protocols don't work that way. If they did, it would require that your displays retained state more than they do today.
- tverbeure 3y ago
  FWIW: pretty much all displays have one or two screen buffers today... You need at least one to enable overdrive. And you need a second one for low frame rate compensation.
NavinF 3y ago
Besides the dynamic bandwidth allocation, you pretty much described how USB 4 and all versions of Thunderbolt works. Personally I'd hate to see my display bandwidth drop when I copy files to a flash drive so I'm glad no monitors support that part of your suggestion. Input lag = horrible UX.
- rbanffy 3y ago
  > I'd hate to see my display bandwidth drop when I copy files to a flash drive Well… if you connect the flash drive to the monitor and not the computer that should be expected. OTOH, I’d love to have faster data rates when my monitor image doesn’t change much (such as when I’m writing code or letting the computer move lots of data between external drives.

fleventynine 3y ago

> Let's remove 20% due to 8b/10 encoding Thunderbolt 3 uses 64b/66b encoding (unlike display port 1.2 alt mode), so there's more bandwidth left over for non-display protocols.

dishsoap 3y ago
came here to comment this
fabiensanglard 3y ago
Thank you for pointing out this mistake. So the 40 Gbps value advertised by Intel is not the pre-encoding rate but post-encoding rate. This means TB3 pre-encoding rate is 40.25gbps. Minus encoding we get post-encoding = 40Gbps (before TB headers). This leads me to question my USB maths. E.g.: USB 3.2 Gen 1×1 advertised as 5,000 Mbps, but is that pre-encoding or post-encoding? Is it `5000 Gbps pre-encoding -> 8b/10b > 4000 Gbps` or `6250 Gbps pre-encoding -> 8b/10b > 5000 Gbps` Same question for USB 3.2 Gen 2×1 which uses 128b/132b (I double checked this time :P!).
- _kb 3y ago
  USB 3.2 gen 1x1 is a 5Gbps data rate. With the 8b/10b coding that provides 500MB/s throughput. USB 3.2 gen 2x1 runs at 10Gbps. After the 128b/132b coding this provides 1212MB/s.
- Kirby64 3y ago
  USB-IF defines their data rates in terms of link rate. So 5 Gbps after 8b10b encoding is 4 Gbps. Makes sense, since fastest transfers never exceed 500 MB/s over USB3. Same applies for the 128b/132b variant, except it's only a ~3% speed reduction, so it's much harder to see that in practical testing.

rnantes 3y ago

Excited to upgrade to a Mac with Thunderbolt 5 which should allow for 6K at 120Hz with 10 bit color over a single cable. All this with an OLED panel is just about peak display for me.(though miniLED would be fine too)

peebeebee 3y ago
Add a nice integrated iPhone quality webcam, and I think it would be endgame display. If there is one company that could do this, it would be Apple. Although I have an LG Ergo 4k 32inch at home and I think the 16:9 ratio is just not enough for having 2 windows side by side. You'd only get 1500pixels per window on retina 6K. I would've liked it to be a bit wider. Or maybe I'd go for a smaller 27 inch, and put my laptop screen as a secondary screen next to it.

tambourine_man 3y ago

That Al Gore setup is really awesome, specially for 2007.

mistersquid 3y ago
> That Al Gore setup is really awesome, specially for 2007. Yeah, the OP links to an image of Al Gore in front of 3 displays with the caption Climate central Gore in his Nashville home office. where he wrote his new book. Mind map software and huge Post-it notes help him order his thoughts [0] I did some medium-searching but couldn't come up with a name for the mind mapping software Gore used. Also interesting is how the 3 displays present in aesthetically pleasing way because they are identical (resolution, size, bezels, etc). [0] https://fabiensanglard.net/xdr/al.webp https://fabiensanglard.net/xdr/al.webp
- tambourine_man 3y ago
  Those are the 30” Apple Cinema Displays, if I’m not mistaken. I dreamed of having one of them. 3 is just preposterous
  - kalleboo 3y ago
    When I was in Uni I got a remote side gig developing some software. I spent my whole first paycheck on a 30" Cinema Display, replacing a rig of 3 hand-me-down CRTs. Never regretted it for a second, that thing was pure luxury.
- NikkiA 3y ago
  > I did some medium-searching but couldn't come up with a name for the mind mapping software Gore used. Purely a guess, but probably OmniGraffle back then.

gatkinso 3y ago

I have one, its amazing obviously but the backlighting is not 100% perfect. Looking forward to the next one of course. I even got it to work with my PC via a [Belkin VR cable](https://www.belkin.com/support-article/?articleNum=316883 https://www.belkin.com/support-article/?articleNum=316883). Even has USB support.

knodi 3y ago

I'm really waiting on a new version of XDR to get one.

huy-nguyen 3y ago

The article states the wrong resolution for the Apple display and it’s an interesting mistake because these days there are actually 2 versions of 6K in consumer-marketed computer monitors: the one used by the Apple display (6016x3384) and the slightly larger one used by the Dell U3224KB 6K that came out earlier this year (6144 x 3456). In fact, an interesting thing people found out when they use the Dell 6K display on Intel MacBook Pros running Mac OS between 10.15 and 13.6 is that the Mac cannot do Display Stream Compression at the Dell's native 6144 x 3456, hence the Mac can only drive the monitor at 30hz instead of 60hz. However, if they can fool the Mac into thinking the display is 6016x3384 (same as the Apple display), DSC magically works and they get 60hz on the Dell (at the expense of sacrificing some screen real estate). Apple must probably hardcode the 6016x3384 resolution somewhere in their OS code. Thankfully people report that this problem has been fixed as of Mac OS 14.1 but that bug existed for 4 years. Edit: this problem only seems to happen on Intel, not Apple silicon machines.

sinfulprogeny 3y ago
> that the Mac cannot do Display Stream Compression at the Dell's native 6144 x 3456, Can't, or won't? M1 MacBook pros for some reason can't do 4k120 over hdmi unless you buy a specific usbc-hdmi adapter and fool it into thinking it's displayport (or something like that, I'm paraphrasing. You can find info if you search for cablematters DDC 4k120 m1.)
- wtallis 3y ago
  There's no "fool it into thinking it's displayport". What you're describing is having the Mac actually literally emit a DisplayPort signal, and a separate device converting that to an HDMI signal. The USB-C HDMI Alt mode standard was never implemented by any real products, and all USB-C to HDMI converters are active adapters that consume DisplayPort signals and emit HDMI signals. Not all of those support HDMI 2.1, which introduced a drastically different signalling mode for HDMI in order to support much higher data rates (and also added display stream compression, further increasing the maximum resolution and refresh rate capabilities).

pram 3y ago

It’s not the thunderbolt controller totally, the Vega and GCN (RX580 etc) Radeon cards on older Macs don’t support DSC. The 16 inch MBP had RDNA cards (which do) For example the Vega MPX cards on the Mac Pro don’t do it, but the 5700 etc cards will give you the added port bandwidth.

bastard_op 3y ago

Apple's got nothing left to offer here, Thunderbolt died with their relation to intel. It's a corpse still running.

bastard_op 3y ago

You wanted really 4k over that? Silly human.

bastard_op 3y ago

So I test this theory daily, I run 2/3 full 4k desktops, 30/60hz when I can get it, but it's a desktop under linux. Kde is ass, so is gnome, not much deals with the hz. I would like one day a desktop that works under linux, I'm trying gnome from kde currently, still a mess.

jiggawatts 3y ago

One thing I'm jealous of as a Windows user is that HDR "just works" in the Apple ecosystem. I was just watching a YouTube video describing how to edit HDR videos in DaVinci Resolve, and step #1 was basically: "Get a Mac". There is simply no monitor equivalent to the Apple Pro Display XDR available from any other vendor, short of the ludicrously expensive Sony mastering monitors that are made to order. There are no 4K OLED HDR monitors that can hit 1,000 nits, for example. Meanwhile my local electronics store has an entire row of TVs with that spec! There are 6K and 8K monitors... but they don't do HDR, or do it so badly that it's actually making things worse. Even if there was proper HDR display for PCs, or if I simply forked over $5K for the Apple XDR monitor... it wouldn't work. Not in practice, not for video editing or for photography. There's something fundamentally broken with the entire Windows and Linux ecosystems that it has been a decade of widespread HDR support everywhere else, but in the PC world it's just crickets chirping and wolves howling in the distance.

cardiffspaceman 3y ago

Does this support HDCP? At what maximum distance will it support an encrypted connection?

NavinF 3y ago
Why not use a HDCP stripper (often marketed as a port splitter) and an optical cable? That'll solve both of your problems