USB4 Specification Announced: Adopting Thunderbolt 3 Protocol for 40 Gbps USB

Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by koala_man on Monday March 04, 2019 @03:48PM (#19305268)

tl;dr: Intel made Thunderbolt 3 royalty free in 2018, so now it's essentially being adopted as USB4.

I had to look up what the point of 40Gbps was, and the industry evangelization site https://thunderbolttechnology.net/ explains that it will allow driving one 5k display or two 4k displays, which is not possible with the 20Gbps offered by USB 3.2 or Thunderbolt 2.

This also helps external GPUs, where TB2/USB3.2 is the equivalent of 2.5 PCI-e 3.0 lanes, while TB3/USB3 is 5.

With that, it seems the goal is to be a viable alternative to PCI-e and HDMI, rather than just improve on today's USB3 speeds for existing device classes.

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by gumby on Monday March 04, 2019 @04:24PM (#19305685)

Thunderbolt is PCIe so instead of a backplane you can use a cable. So basically anything you'd use PCIe for (drives, external GPUs etc) you can use TB for.

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by edwintorok on Monday March 04, 2019 @06:36PM (#19306776)

I'd be wary of plugging thunderbolt devices in, see http://thunderclap.io/

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by woolvalley on Monday March 04, 2019 @04:32PM (#19305768)

Not quite, because the equivalent pure pcie connection is faster than thunderbolt due to the overhead in thunderbolt.

We need another doubling in thunderbolt's speed for it to not have a penalty when using eGPUs

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by gumby on Monday March 04, 2019 @04:58PM (#19306017)

It's been a few years since I was programming those things but IIRC the TB 3frames are comparable to PCIe 3 frames (terminology is slightly different between the two).

The real thing is that TB3 only has four lanes while Intel's server (and I believe some desktop) chipsets have 16-lane PCIe. Not sure about the mobile chipsets (again, I no longer follow this as closely/ as I used to). So indeed you won't be able to pump data into an eGPU as quickly as you could a high performance internal one. Or perhaps we should add "yet"?

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by artiscode on Monday March 04, 2019 @03:52PM (#19305322)

Does 40Gbps mean two 4K displays daisy chained?

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by lxmcneill on Monday March 04, 2019 @04:03PM (#19305459)

In theory, yes. Since driving one 60hz 4k display at 4:4:4 chroma takes roughly 18gbps then daisy chaining 2 displays should be possible.

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by syn0byte on Monday March 04, 2019 @04:14PM (#19305584)

It just means on the spec sheet its enough bandwidth for 2 4k streams. (HDMI 1.4 4k@60FPS == ~18Gbps)

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by monocasa on Monday March 04, 2019 @04:04PM (#19305464)

Yeah. One 4k60 screen is between five and six gbps.

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Re:USB4 Specification Announced: Adopting Thunderbolt 3 Prot... by nfriedly on Monday March 04, 2019 @04:13PM (#19305575)

Yes, or with a hub.

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