Do I need Thunderbolt 3 or USB 3.1?

[AppleFanBoy888]

Hi,

I was about to pull the trigger on a maxed-out iMac 5K and stopped after reading something about Thunderbolt 3 (using USB Type C) and USB 3.1 coming out soon. I want the iMac 5K to last at least 4 years. Do I need it?

For Apps I use are Safari, iTunes, Parallels, Photoshop, Final Cut Pro, Microsoft Office, SolidWorks CAD, Xcode

Thanks

 

[LiveM]

Well, Apple is very slow with USB but Thunderbolt 3 will allow external GPUs, which has the potential to address the biggest weakness of Macs. By the same token, old Macs might plummet in value.

Otherwise, Thunderbolt 3 probably isn't that important as Macs still can't process data fast enough for Thunderbolt 1.

 

[Samuelsan2001]

Hi,

I was about to pull the trigger on a maxed-out iMac 5K and stopped after reading something about Thunderbolt 3 (using USB Type C) and USB 3.1 coming out soon. I want the iMac 5K to last at least 4 years. Do I need it?

For Apps I use are Safari, iTunes, Parallels, Photoshop, Final Cut Pro, Microsoft Office, SolidWorks CAD, Xcode

Thanks

Unless you plan on using external GPU's or a second 5k screen it will mean nothing to you.

 

[theluggage]

I want the iMac 5K to last at least 4 years. Do I need it?

Probably not. Obviously its not going to be cutting edge in 4 years time, but its hardly going to be landfill.

At the moment, Thunderbolt 3 peripherals are like hen's teeth and you'd need a $100 adapter (not yet available) just to connect an "old" Thunderbolt 2 peripheral to your TB3 computer. USB-C is a bit further on (and more likely to become mainstream), but not much. Always remember: the early worm gets the bird! (This from someone with a 2011 MacBookPro with a single TB port that doubles as the only external display connector: forget all those cheaper TB devices that don't have a through port!)

Frankly, I'd give 50:50 odds as to whether Thunderbolt 3 will make or break Thunderbolt: the ability to hook cheap USB devices to a Thunderbolt port might be a plus, but that could cannibalise the sales of 'cheap' prosumer TB3 devices and make TB even more restricted to customers with specialised needs and deep pockets. Any hitches with intercompatibility between 'regular USB-C' and 'TB3+USB-C' devices could give TB3 a bad rep. The distinction between "Thunderbolt 3 displays" (5k via 2 x DisplayPort 1.2 ports multiplexed on a single cable using TB protocols) and "USB-C displays" (5k via a single DisplayPort 1.3 port using selected wires in a USB-C cable) sounds like a recipe for confusion, too.

I'd guess TB2 is still going to be supported for 3-4 years (some TB2 products have only been launched recently) - it will be some time before a majority of users have TB3. USB 3.1/USB-C is backward-compatible with USB, just as most USB 3 devices work (albeit more slowly) with USB 2 hosts.

I'd guess that displayPort-over-USB-C might become the standard for external displays in a few years, but mini-DisplayPort-to-USB-C monitor should be a simple adapter (and look how long VGA and DVI ports have taken to disappear from monitors).

A Thunderbolt 2 to USB 3.1 adapter ought to be feasible (if there's demand).

 

[campyguy]

Clearing up a bit of incorrect items here. FWIW, I'm waiting for the port refresh - I had to wade through those questions myself.

"USB 3.1" has been around since 2013, and widely available since early last year - it's also called USB SuperSpeed+ or SuperSpeed USB 10 Gbps. It's on several of our Win workstations.

"USB-C" is a port interface style. That's it, nothing more.

TB3 includes USB 3.1 Gen 2. TB3-capable devices will, at least those already demoed to me use the USB-C style port interface. My vendors have indicated that there will be "passive" TB3 cables, which will connect a Mac/PC to a USB 3.1 device but will not include all of the other options (PCIe, dual-directional power, DP, muxing/demuxing, daisy chaining...). FWIW, TB3 still includes the older DP 1.2 "standard" (HBR2 and MST); I'm surmising that Apple screwed up here but for there's hundreds of millions of older displays out there that won't be upgraded anytime soon...

The important part - for me - is that TB3 includes HDMI 2.0, which addresses the want/need for 10-bit color (present on/built-in into newer rMBPs and iMacs). I haven't looked for adapters, but the present high-speed HDMI cables carry enough bandwidth for this. I think that Accell is the only manufacturer that makes an adapter for DP 1.2>HDMI 2.0 connections that address the 10-bit color space...

There won't be any TB2>USB 3.1 adapters/cables. TB2 and USB 3.1 and TB2 and USB 3.0 (Gen 2, also 10 Gbps throughput) are incompatible technologies; TB2 and USB 3.0 (Gen 1) are compatible technologies, but it's cheaper just to buy a decent/shielded USB 3 Gen 1 cable...

As for DP 1.3 over the USB 3.1 connector, I'll hazard a bet that Apple and Intel will be pushing vendors/manufacturers to push for TB3 options as DP over USB-C is - IMHO - barely an improvement over the best DP or mDP>DP cables available today. USB 3.1 offers a 10Gbps max throughput while the Accell mDP>DP cables I use provide a 8.1Gbps max throughput (http://www.anandtech.com/show/8558/displayport-alternate-mode-for-usb-typec-announced), although the Accell cables I use are likely a huge improvement over the crap cables shipped with and attached to most displays in the world. You might find that the new cables are a huge improvement, but I'll offer that they're not much better than what I've already been using with my 4k displays...

As for "making or breaking" Thunderbolt, with the new port interfaces and Intel dropping their "entry tax", my vendors are demoing laptops and desktops for our CAD work - every single one of them has TB3, as do some of the demo displays, eGPUs, and storage devices. Intel seems to want to sell this product now. As for LiveM's comment, I agree - Intel's new commitment seems to be dropping the entry cost of TB3 devices (at least, those my vendors are hawking to me) - no more "it's $200 for the USB 3 thingy but it's $400 for the TB thingy...".

There's no way I'm buying a new iMac now. I'll either buy the new iMac or go for the deeply-discounted old iMac once the refresh is announced in a few weeks... And, I'm selling a few older Macs before their resale value tanks - I'm already seeing this in the Win laptop space, but not in the Win desktop space as its just a card/driver install to address this...

 

[theluggage]

My vendors have indicated that there will be "passive" TB3 cables, which will connect a Mac/PC to a USB 3.1 device but will not include all of the other options (PCIe, dual-directional power, DP, muxing/demuxing, daisy chaining...).

That sounds like a USB-C cable, not a thunderbolt cable.

AFAIK there are going to be:
* Active 40 Gb/s thunderbolt cables
* Short passive 40 Gb/s thunderbolt cables
* Passive 20 Gb/s thunderbolt cables
* At least 3 different grades of USB-C cable that don't support thunderbolt
* Rubbish USB-C cables that fry your computer.

...I think all the passive TB cables offer all the USB-C bells and whistles (power, DisplayPort) etc. which overlap somewhat with USB-C features.

FWIW, TB3 still includes the older DP 1.2 "standard" (HBR2 and MST); I'm surmising that Apple screwed up here but for there's hundreds of millions of older displays out there that won't be upgraded anytime soon...

Yeah, seems pretty clear that DP 1.2, and not 1.3 is baked in to the Thunderbolt 3 spec whereas USB-C in DisplayPort 'alternate mode' supports 1.3 (although since USB-C is a multi-vendor spec, that doesn't mean that all implementations will support it). I think this is Intel - from their POV its moot since none of their GPUs feature DP1.3 yet, but its dumb that we'll need Thunderbolt 4 when they (or other discrete GPUs) do... The kicker is that DP1.3 supports -true' 5k whereas DP1.2 has to treat it as two displays. TB3 can carry two 'virtual' cables worth of DP1.2 data - but only to a TB-equipped display.

The important part - for me - is that TB3 includes HDMI 2.0, which addresses the want/need for 10-bit color (present on/built-in into newer rMBPs and iMacs). I haven't looked for adapters, but the present high-speed HDMI cables carry enough bandwidth for this. I think that Accell is the only manufacturer that makes an adapter for DP 1.2>HDMI 2.0 connections that address the 10-bit color space...

There won't be any TB2>USB 3.1 adapters/cables. TB2 and USB 3.1 and TB2 and USB 3.0 (Gen 2, also 10 Gbps throughput) are incompatible technologies; TB2 and USB 3.0 (Gen 1) are compatible technologies, but it's cheaper just to buy a decent/shielded USB 3 Gen 1 cable...

A TB2 -> USB 3.1 'adaptor' would be a device containing a TB controller and a PCIe USB 3.1 controller (just like a TB-to-Ethernet or TB-to-Firewire 'adaptor'). TB2 and USB 3.0 are no more compatible than TB3 and USB 3.1.

As for DP 1.3 over the USB 3.1 connector, I'll hazard a bet that Apple and Intel will be pushing vendors/manufacturers to push for TB3 options as DP over USB-C is - IMHO - barely an improvement over the best DP or mDP>DP cables available today.

Except, as per the article you linked, USB-C DisplayPort alternate mode doesn't rule out DP 1.3 the way that TB3 does (the proof of the pudding will be how that translates into reality). Also, a DisplayPort display simply needs a passive adapter to support USB-C DisplayPort Alternate mode (which simply assigns some of the USB-C wires to DisplayPort and leaves the rest for USB) whereas a DisplayPort-over-TB3 display needs a TB controller to extract the DisplayPort signal and a PCIe USB controller to provide any other connectivity.

There's no way I'm buying a new iMac now. I'll either buy the new iMac or go for the deeply-discounted old iMac once the refresh is announced in a few weeks...

There's no particular reason to believe that Apple will refresh the iMac in a few weeks. It could happen, but the rumors have all been about iDevices and watch straps...

 

[campyguy]

That sounds like a USB-C cable, not a thunderbolt cable.

AFAIK there are going to be:
* Active 40 Gb/s thunderbolt cables
* Short passive 40 Gb/s thunderbolt cables
* Passive 20 Gb/s thunderbolt cables
* At least 3 different grades of USB-C cable that don't support thunderbolt
* Rubbish USB-C cables that fry your computer.

...I think all the passive TB cables offer all the USB-C bells and whistles (power, DisplayPort) etc. which overlap somewhat with USB-C features.

Not picking nits here, USB-C is the port configuration, USB 3.1 Gen 2 is the data protocol. The cables my vendors are demoing me carry PCIe, USB 3.1 Gen 2, dual directional power, and DP 1.2 - the only element that's missing is the muxing/demuxing and daisy chaining capabilities present in TB3 but not present in USB 3.1 Gen 2. What isn't clear yet to my vendors, and by proxy, me is what the data transmission rate will be over these passive cables.

Yeah, seems pretty clear that DP 1.2, and not 1.3 is baked in to the Thunderbolt 3 spec whereas USB-C in DisplayPort 'alternate mode' supports 1.3 (although since USB-C is a multi-vendor spec, that doesn't mean that all implementations will support it). I think this is Intel - from their POV its moot since none of their GPUs feature DP1.3 yet, but its dumb that we'll need Thunderbolt 4 when they (or other discrete GPUs) do... The kicker is that DP1.3 supports -true' 5k whereas DP1.2 has to treat it as two displays. TB3 can carry two 'virtual' cables worth of DP1.2 data - but only to a TB-equipped display.

The important part - for me - is that TB3 includes HDMI 2.0, which addresses the want/need for 10-bit color (present on/built-in into newer rMBPs and iMacs). I haven't looked for adapters, but the present high-speed HDMI cables carry enough bandwidth for this. I think that Accell is the only manufacturer that makes an adapter for DP 1.2>HDMI 2.0 connections that address the 10-bit color space...

I've had a few spirited discussions with my coworkers and here in the MR Forums about relevant Accell DP or mDP>DP cables. My 25-odd employees are on Macs and Windows workstations, myself included. Their - and my - gripes were about external display performance and computer operating temperatures - those complaints aren't new in my experience as I've been in engineering/architectural offices since the late 80s (yep, I'm old...). My point here is that the bottleneck always came down to the cable and/or the supporting drivers, but my Win boxes have exactly the same issues as my Macs. After a bit of research it came down to the cables - I found that the only cables I could buy with the "biggest pipes" were certain cables made by Accell, and it's not about DP 1.2 - it's about the amount of bandwidth those cables carry, as in the new "data hose" is bigger than those we were using by a factor of around 60%. TB3 offers DP 1.2 compatibility, but I want to know what the actual data rate is going to be (not the marketing hype...) - if it's DP 1.2 but only up to 1600p or 1440p, then the Accell cables we're using offer more throughput at DP 1.2 2160p, so there's no reason for me to "upgrade"...

The Accell cables we're using work great with 10-bit color, but only on our PCs right now as we're still on 8-bit Macs for now. I prefer a $15 or $20 Accell cable over a $50 TB3 cable, so there's waiting for the cost of those nifty TB3 cables to be made public.

A TB2 -> USB 3.1 'adaptor' would be a device containing a TB controller and a PCIe USB 3.1 controller (just like a TB-to-Ethernet or TB-to-Firewire 'adaptor'). TB2 and USB 3.0 are no more compatible than TB3 and USB 3.1.

Except, as per the article you linked, USB-C DisplayPort alternate mode doesn't rule out DP 1.3 the way that TB3 does (the proof of the pudding will be how that translates into reality). Also, a DisplayPort display simply needs a passive adapter to support USB-C DisplayPort Alternate mode (which simply assigns some of the USB-C wires to DisplayPort and leaves the rest for USB) whereas a DisplayPort-over-TB3 display needs a TB controller to extract the DisplayPort signal and a PCIe USB controller to provide any other connectivity.

The only hole in the TB2>USB Gen 2 converter is as far as my vendors know, nobody's making that chipset. TB1/2 carries DP 1.1a - a built-in limitation I would pass on. Intel's lowered the cost of the 3 variants of TB3 chipsets so much that TB2 is already more expensive (the perceived "Mac Tax", even though we know that's pretty much crap). Then there's my vendor feedback that their clients stopped buying TB2 stuff months ago and that drivers are being written for the new shiny stuff - I buy by the end of the year so I can write off certain expenditures, much like my competitors, and my vendors have lots of TB2 products gathering dust.

The killer is that TB2 carries only USB 3.0, which is as slow as 3.1 Gen 1 - SS is good for 5 Gbps. If it were my business, that's a bottleneck that's "fixed" by a $5 USB cable. My Win boxes have Gen 2 cards in them, supported by drivers from their manufacturers. AFAIK, Apple hasn't written any Extensions to work with USB 3.1 Gen 1 or 2, although we'll see the latter pretty soon. I just don't see that TB2>USB 3.1 Gen 2 box being built any time - but some of the laggard Mac vendors like Sonnet might come out with one, but it'll be gimped IMHO...

Then, regarding USB 3.1 Gen 2 support, we have to turn to Apple for the three most important bits - Drivers, Drivers, and Drivers. Without those 3 bits, we're stuck again with expensive peripheral options or doorstops...

There's no particular reason to believe that Apple will refresh the iMac in a few weeks. It could happen, but the rumors have all been about iDevices and watch straps...

There's no reason, yes, I agree. My vendors know I use Macs, and they know about product delivery schedules better than I do - largely because I have working hardware I generally don't care, and I know they just want my money in their pocket. Win laptops are showing up with TB3/USB-C ports, but my vendors know that they make more money on the peripherals and client support - they know better than to bother me with crap I can't use (like Apple Watches!), so I'm surmising that they're getting more active because they know something I don't. The ATV4 has a USB-C port, and that was a surprise at the time - I like surprises Apple, so, where's my new iMac? Cheers!

 

[theluggage]

Not picking nits here, USB-C is the port configuration, USB 3.1 Gen 2 is the data protocol.

I think there's some confusion here (because its confusing):

USB-C connections can carry multiple protocols including USB1,2,3,3.1,3.1G2, DisplayPort (1.3), PCIe and Thunderbolt 3 by physically assigning some or all of USB-C's 4 pairs of signal wires to that protocol. Potentially you can have a passive cable connecting a USB-C port 'output' to, say, a DisplayPort input or a display that routes some pairs to the display and others to the USB port.

Thunderbolt signals carry multiple protocols (principally PCIe and DisplayPort 1.2) in a different way: by multiplexing several of them together into a Thunderbolt signal sent over a single pair of wires. However, that means that both devices need a thunderbolt controller to decode the signals.

Thunderbolt 1 and 2 had a second trick whereby the whole Thunderbolt port morphed into a MiniDisplayPort if a DisplayPort cable/adapter was connected. I'm guessing that this is redundant in Thunderbolt 3 since the USB-C port's alternate mode does the job better. However, since thunderbolt-enabled USB-C ports will be driven by the Intel chipset, I'm guessing this will still be limited to DP 1.2.

The cables my vendors are demoing me carry PCIe, USB 3.1 Gen 2, dual directional power, and DP 1.2 - the only element that's missing is the muxing/demuxing and daisy chaining capabilities present in TB3 but not present in USB 3.1 Gen 2. What isn't clear yet to my vendors, and by proxy, me is what the data transmission rate will be over these passive cables.

Simple: If they have the 'pitchfork' logo, 'SS' and '10' on them then the maximum data rate should be the max for USB 3.1 Gen 2: 10 Gbps - and if they don't, you send 'em back because they're fake.

What is uncertain is whether they'll work as passive Thunderbolt cables for Thunderbolt devices at 20Gbps but, unless they have that little lightning bolt symbol on them showing that they're TB certified, you have no comeback if they don't.

I think the 'active' 40Gbps thunderbolt cables are going to have the lightning bolt and a '3' - or something.

and it's not about DP 1.2 - it's about the amount of bandwidth those cables carry

They're digital cables: Digital cables come in three sorts: (a) conforming-to-spec (b) faulty and (c) fake. If it says DP1.2 they're supposed to carry the bandwidth specified by DP1.2. Yes, faulty/fake cables are a problem and I'm sure there will be fake TB 3 cables in circulation.

The Accell cables we're using work great with 10-bit color, but only on our PCs right now as we're still on 8-bit Macs for now. I prefer a $15 or $20 Accell cable over a $50 TB3 cable, so there's waiting for the cost of those nifty TB3 cables to be made public.

You won't want TB3 cables - you'll need USB-C to DisplayPort cables (or USB-C to USB-C cables if its a new display with USB-C). Maybe the passive TB-logo'd cables will have had stricter certification (but that won't stop counterfeits). Unless its a Thunderbolt display (with a thunderbolt controller) which is not the same as a DisplayPort display that has a USB-C connector.

(You know I said TB3 could make or break Thunderbolt - this confusing stuff is one of the ways it could break it).

The only hole in the TB2>USB Gen 2 converter is as far as my vendors know, nobody's making that chipset.

You don't need a chipset: it would consist of a TB2 controller to extract the PCIe and a bog standard PCIe-to-USB3.1 controller. That's how the Apple TB-to-Ethernet and TB-to-Firewire dongles work. All it really needs is demand.

The killer is that TB2 carries only USB 3.0,

TB2 doesn't 'carry' USB 3 - it carries PCIe which drives a regular PCIe-to-USB controller. Yes, it would need Apple (or someone) to write USB 3.1 G2 drivers for the controller in question. Yes, many of the TB hubs that came out have been gimped (I think that's what happens when you design-in 2-year obsolescence and then hit 2 year production delays).

Win laptops are showing up with TB3/USB-C ports

Windows PCs were showing up with USB 1 ports and no peripherals for a year or so before the iMac came out with only USB ports - then it took off.

 

[campyguy]

I think there's some confusion here (because its confusing):

USB-C connections can carry multiple protocols including USB1,2,3,3.1,3.1G2, DisplayPort (1.3), PCIe and Thunderbolt 3 by physically assigning some or all of USB-C's 4 pairs of signal wires to that protocol. Potentially you can have a passive cable connecting a USB-C port 'output' to, say, a DisplayPort input or a display that routes some pairs to the display and others to the USB port.

Thunderbolt signals carry multiple protocols (principally PCIe and DisplayPort 1.2) in a different way: by multiplexing several of them together into a Thunderbolt signal sent over a single pair of wires. However, that means that both devices need a thunderbolt controller to decode the signals.

Thunderbolt 1 and 2 had a second trick whereby the whole Thunderbolt port morphed into a MiniDisplayPort if a DisplayPort cable/adapter was connected. I'm guessing that this is redundant in Thunderbolt 3 since the USB-C port's alternate mode does the job better. However, since thunderbolt-enabled USB-C ports will be driven by the Intel chipset, I'm guessing this will still be limited to DP 1.2.

Simple: If they have the 'pitchfork' logo, 'SS' and '10' on them then the maximum data rate should be the max for USB 3.1 Gen 2: 10 Gbps - and if they don't, you send 'em back because they're fake.

What is uncertain is whether they'll work as passive Thunderbolt cables for Thunderbolt devices at 20Gbps but, unless they have that little lightning bolt symbol on them showing that they're TB certified, you have no comeback if they don't.

I think the 'active' 40Gbps thunderbolt cables are going to have the lightning bolt and a '3' - or something.

They're digital cables: Digital cables come in three sorts: (a) conforming-to-spec (b) faulty and (c) fake. If it says DP1.2 they're supposed to carry the bandwidth specified by DP1.2. Yes, faulty/fake cables are a problem and I'm sure there will be fake TB 3 cables in circulation.

You won't want TB3 cables - you'll need USB-C to DisplayPort cables (or USB-C to USB-C cables if its a new display with USB-C). Maybe the passive TB-logo'd cables will have had stricter certification (but that won't stop counterfeits). Unless its a Thunderbolt display (with a thunderbolt controller) which is not the same as a DisplayPort display that has a USB-C connector.

(You know I said TB3 could make or break Thunderbolt - this confusing stuff is one of the ways it could break it).

You don't need a chipset: it would consist of a TB2 controller to extract the PCIe and a bog standard PCIe-to-USB3.1 controller. That's how the Apple TB-to-Ethernet and TB-to-Firewire dongles work. All it really needs is demand.

TB2 doesn't 'carry' USB 3 - it carries PCIe which drives a regular PCIe-to-USB controller. Yes, it would need Apple (or someone) to write USB 3.1 G2 drivers for the controller in question. Yes, many of the TB hubs that came out have been gimped (I think that's what happens when you design-in 2-year obsolescence and then hit 2 year production delays).

Windows PCs were showing up with USB 1 ports and no peripherals for a year or so before the iMac came out with only USB ports - then it took off.

Gotta hit the road for meetings, I was wrong on the TB2/USB3 bit (emboldened), long day, not enough sleep... My bad, and I've got to lump things together here...

Yes, there's some confusion here. I think we both have valid points. The thread is more-or-less about cables, which - to me - is often the bottleneck in a workflow. Where my head is at with this - I'm thinking in the vein of the computer>cable>peripheral perspective, following:

• Apple's TB2 ports also convey DP 1.2 - but I've yet to find a single TB cable that conveys DP 1.2 - even Apple's $60 cable or Corning's $1000 cable convey DP 1.1a. Nobody's built a TB cable that conveys DP 1.2, so, in my mind, DP over TB1/2 is 1.1a and any other point is moot (using the context here is that TB1/2 relevant to DP 1.2 is of no practical significance - it could exist, but it doesn't exist; I'm surmising here that most of the world is happy with the cheap DP cables that shipped with the displays on their desk). TB cables are IMO not the best display cables for DP-capable displays. A cheap $6 DP 1.2 cable can move more data to a DP display than any TB cable can; my issue with cheap DP cables is that almost every one I've tested myself returns power back to a Mac/PC over Pin 20, with the Accell cables not returning power over Pin 20 and having the most bandwidth capability over DP (listed at up to 2160p, while all the others on the DP web portal are no greater than 1600p).
• By the above logic - generally I'd agree with you in that someone can make a box (I think in the terms "chipset") that converts TB2 to some faster flavor of USB. My only contention is that there's a tiny market for that box. A TB2 chipset runs about $50 or so. Everyone I know that "needs" 10 Gbps+ speed either already has it - it's on my PCs via $10 cards or my Macs via TB peripherals - or they're waiting for the new products to get on the market. I don't disagree with you here, I think they just won't sell and that's why they don't and won't exist anytime soon...
• Just one more bit, do read up on DP 1.2 - I did. Think "garden hose" in terms of potential volume capacity - yes, there are DP 1.2 cables, but read the actual specs on those cables and the Wiki. Also read about the issues about returning power over Pin 20. All garden hoses pretty much do the same job, but larger diameters potentially move more volume over time. The Accell DP 1.2 cables I chose don't return power over Pin 20 (part of the DP spec) and have the fattest "pipes" I could find (at any price, but still a reasonable $15 each). My Macs and PCs run cooler, EDID data from my displays are properly conveyed without hacks, and the displays' match our line/graphics output now. My additional point here is that I want to see those new USB-C and TB3 cables' specs before buying and/or passing judgment on them.

Gotta run! Cheers!

 

[theluggage]

Apple's TB2 ports also convey DP 1.2 - but I've yet to find a single TB cable that conveys DP 1.2 - even Apple's $60 cable or Corning's $1000 cable convey DP 1.1a

I'm trying to work out exactly what you're doing here.

There are two distinct and very different ways that Thunderbolt 1 & 2 works with DisplayPort:

1. TB 2 Port <------- MiniDP cable -------> DisplayPort Display

2. TB 2 Port <------- TB cable -------> TB peripheral <---- DisplayPort cable ----> DisplayPort Display

It sounds like you're trying to do:

3. TB 2 Port <------ TB cable --------> DisplayPort Display

(If so, you're doing it wrong - if not, apologies & ignore the rest)

In mode (1) the TB port detects that it isn't connected to a thunderbolt device and morphs into a MiniDisplayPort, which sends native DisplayPort signals from the GPU down the DP cable to the display.

In mode (2) the TB port moshes the DisplayPort data together with PCIe data into a Thunderbolt signal, sends it over the active Thunderbolt cable, to the peripheral where the TB peripheral controller splits the PCIe and DP parts so it can be sent natively to a DisplayPort display (either built-in, if its a thunderbolt display, or to the second TB port in MiniDP mode, or to a DP-to-HDMI converter in most docks).

Mode (3) shouldn't work at all because a TB 1/2 cable isn't a Displayport cable, it is an active cable (with a cable driver chip in each plug) purely intended to carry Thunderbolt signals.

TB3 gets more complicated because you have 'active' and 'passive' TB cables - I think the 'passive' ones are interchangeable with regular USB-C cables and have simply been Thunderbolt certified while the active ones are TB only and might work in mode (3) above.

 

[campyguy]

I'm trying to work out exactly what you're doing here.

None of what followed. I moved me and my company off of cheap non-compliant DP cables and TB cables relative to displays - I'm the boss, so that decision was my call - but only after some research on my part. All of our Macs have two TB2 ports and all of our PCs have at least 3 TB2 ports. Myself, and the company, use zero TB displays but use about 60 DP 1.2-compliant displays (3 at some workstations, 2 at all the rest, and 2 attached to my personal rMBP.

TB cables are IMHO lousy display cables - it's really old tech for displays. Our TB storage devices are connected to our hubs/PCs/Macs via one TB port - temporarily, then disconnected. Most of our storage devices are NAS devices connected via gigabit Ethernet or a very-high-speed router that employs link aggregation, which is pretty much irrelevant for this thread.

Here's my take, as we use peripherals and cables for their intended purpose - not just "stick it in and use that cable for everything...". Insert a TB cable, use the computer to connect to a TB peripheral - for my purposes, that's only a couple of TB docks and several TB storage devices. Insert a DP cable, only for the purpose of using a Mac/PC with a display. To qualify, much of my company's work requires "checking in" and "checking out" files - nobody gets unfettered access to digital files, but IMHO there's no reason to keep a peripheral attached to a device longer than it needs to be accessed. Windows' propensity to "touch" and "time-out" network drives is the factor that drives this decisions - Windows is a PITA here, but it drives our workflow.

Also, IMHO it's a matter of using the right tool for the job. TB cables are great for solid data transfer, not so much for display tech. Compliant DP cables are great for, well, connecting computers to displays and that's about it - my only analogy here is that my Wiha tools last years, but the crap sold at Harbor Freight lasts about one use - I use my displays every day so why not buy the best.

As to further prognostication regarding the new stuff, I'm with you on this. My vendors are hawking lots of goods - I'm waiting to see what actually works before writing a check. I'm waiting until Dell (my PC vendor - yeah, it's Dell but their stuff is certified for the type of work we do...) and Apple finally settle on before opening up my checkbook. My only rogue comment here - it's about frickin' time that Intel/Apple/MS/Dell/others finally stopped trying to set "standards", as I'm getting too old for this sh..., er, crap...