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USB4 Specification Released
 

USB4 Specification Released  

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SuperCoolBeaver
(@supercoolbeaver)
New Member
Joined: 8 months ago
 

The USB4 Specification was released today. It optionally supports interoperability with Thunderbolt 3 products. You can get from the USB Document Library.

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Ray
 Ray
(@ray)
Eminent Member
Joined: 2 years ago
 

When can we start seeing this make its way into products? And can machines without USB4 but with Thunderbolt 3 (like my 2018 MBP) somehow be updated to support it? I doubt do because I’d imagine it would need a new controller, BUT if it’s interoperable with Thunderbolt 3, maybe the Thunderbolt controller can be double as a USB 4 controller. Only time will tell I suppose.

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C Films
(@c-films)
Active Member
Joined: 4 months ago
 

Hopefully it means egpus will work with it as well.

Pending: Add my system information and expected eGPU configuration to my signature to give context to my posts


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nu_ninja
(@nu_ninja)
Estimable Member
Joined: 2 years ago
 

I think USB4 with thunderbolt 3 capability will be eGPU compatible, whereas USB4 without thunderbolt/pcie will not. I would hope nearly all USB4 products add the thunderbolt/pcie functionality.

From what I've read, USB4 will be backwards compatible with previous USB's. Combined with TB3 interoperabiltiy, I think this means USB4 devices will work with TB3 ports OOB, at least in some capacity.

Mid-2012 13" Macbook Pro (MacBookPro9,2) TB1 -> RX 460/560 (AKiTiO Node/Thunder2)
+ macOS 10.15+Win10 + Linux Mint 19.1


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odin
 odin
(@odin)
Trusted Member
Joined: 1 year ago
 
Posted by: @ray

When can we start seeing this make its way into products? And can machines without USB4 but with Thunderbolt 3 (like my 2018 MBP) somehow be updated to support it? I doubt do because I’d imagine it would need a new controller, BUT if it’s interoperable with Thunderbolt 3, maybe the Thunderbolt controller can be double as a USB 4 controller. Only time will tell I suppose.

Probably late 2020 early 2021, and then consider a long period of trickling out of products and refining software.

This post was modified 3 months ago

LG Gram 17 | Sonnet Breakaway Box 550 | Asus Strix RTX 2070 OC Edition | Win 10 Pro 1903 + Fedora 31 Dual Boot
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kumowoon1025
(@kumowoon1025)
Active Member
Joined: 2 years ago
 

Woah, it looks like USB's actually going to be an actual bus...
I guess that's somewhat expected from it tunneling TB3, but now I wonder if hubs are going to be really expensive with tcams and everything basically being multilayer switches??

2018 Mac mini I7 - Sonnet BB550W + Gigabyte RX570 4GB - Alpine Ridge AIC – (TB3 to TB adapter) – Apple Thunderbolt Display
2019 15" MBP i9 also works as expected in above setup
2012 15" rMBP works with purge-wrangler
All on 10.14.6 (18G84/b) for debug kernel...
iMac14,2, no Built-in LCD, GT 755M dGPU - Bricked after Catalina DP update tried to flash nonexistent T2 chip. Mucking around with Pomona clip, looking for BootROM dump if anyone has one 🙁


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joevt
(@joevt)
Prominent Member
Joined: 2 years ago
 

Some differences between Thunderbolt 3 and USB4:
- USB4 adds USB3.x tunneling (can replace USB PCIe controller with USB hub/controller).
- USB4 has a slightly slower clock (10 or 20 Gbps instead of 10.3125  or 20.625).
- USB4 can have multiple downstream ports (maybe Thunderbolt can too, but Intel only ever produced Thunderbolt chips with two ports and I think a Thunderbolt host is limited to a single PCIe downstream port per USB4 device).
- USB4 max depth is 5 instead of 6.
- USB4 host can have more devices (wider instead of deeper tree).

I tried to find in the spec information on PCIe bandwidth limit (without reading the entire thing). There was mention of balancing latency with performance by changing the amount of buffering (applies to USB and PCIe tunneling).

Mac mini (2018), Mac Pro (Early 2008), MacBook Pro (Retina, 15-inch, Mid 2015), GA-Z170X-Gaming 7, Sapphire Pulse Radeon RX 580 8GB GDDR5, Sonnet Echo Express III-D, Trebleet Thunderbolt 3 to NVMe M.2 case


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 chx
(@chx)
Estimable Member
Joined: 3 years ago
 

 Even as the USB4 specification introduces a new underlying protocol, compatibility with existing USB 3.2, USB 2.0 and Thunderbolt 3 hosts and devices is supported; the resulting connection scales to the best mutual capability of the devices being connected

That's the official word. I think USB 4 devices using the Thunderbolt mode (which seems to be optional) will work TB3 hosts but if they sport USB hubs / devices attached to those then those simply won't work. But, a plain eGPU would work. In the other direction, a TB3 eGPU should work with a full capable USB 4 port.

Lenovo ThinkPad 25 -- GALAX SNPR TB3 1060 -- Lenovo Graphics Dock -- Benq BL2411PT - - two PackedPixels - Dasung not-eReader backer


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