USB Type B Upstream Bandwidth

[Daniel_Herr]

Is the USB B upstream port a 5 or 10 gbps connection?

[Techmo]

According to the Spectrum specs list, the USB type B upstream port is USB 3.1, which has a maximum of 10Gbps of throughput.

Spectrum specs and FAQ - First prototypes

NOTE: A more up-to-date spec sheet and FAQ is available here [sfaqbanner] Hey community, We’ve just revealed our first prototypes, and as with every major update, we’re following up with a deeper dive into what’s changed, an update of our provisional spec sheet, and an update of our frequently asked questions. We’ve updated answers to questions from our previous FAQ where needed, and have added a number of questions that have come in through support and social media, as well as right here in…

[nkyadav]

Yup.

For a breakdown of the confusing things going on in the nomenclature of USB 3.x, take a look at the chart here about 1 page down: https://appuals.com/usb-3-2-nomenclature-and-specifications-explained/

Wish they had just stuck to simple nomenclature - but there you go. USB 3.1 == 10 Gbps max.

[Lore_Wonder]

USB 3.1 Gen 2 supports 10 Gbps bandwidth; however, USB 3.1 Gen 1 supports only 5 Gbps bandwidth but is also under the USB 3.1 naming. From a graph in the article linked by @nkyadav, it appears that Type-B cables support up to USB 3.1 Gen 1.

I am checking with @Kira to confirm the exact bandwidth Spectrum’s Type-B port supports.

[jpetso]

I have a follow-up question to this: Will the maximum frequency (144 Hz for the 4K model, 240 Hz for the QHD) be available for all input plugs, and what speeds will be available for the USB hub at max frequency?

For other monitors, apparently there’s a widespread issue where they’re all shipping with USB 3.0 or USB 3.1 Gen 1 (i.e. same thing) and then people have to choose between either transferring USB-C display data at 4K @ 60 Hz while downgrading the hub functionality to USB 2.0 speeds, or keeping USB 3.x Gen 1 speeds but lowering the framerate to 30 Hz. I would assume that this is due to bandwidth limitations on the USB interface that those monitors use.

Now, Spectrum ships with USB 3.2 Gen 2 for the USB-C upstream, which gives it twice the capacity. I’m guessing that allows for the upgrade to 144 Hz, while probably still having the hub downgraded at full frequency. Is that assumption correct and would we get USB 3.x Gen 1 speeds at 60 Hz display modes? And because USB Type-B doesn’t have DP Alt Mode, it gets those same USB 3.x Gen 1 speeds at its maximum rate for any display input configuration?

Thanks for the research and clarification!

[Lore_Wonder]

@jpetso

Will the maximum frequency (144 Hz for the 4K model, 240 Hz for the QHD) be available for all input plugs, and what speeds will be available for the USB hub at max frequency?

The following quote is the information we have.

@Lore_Wonder

(Spectrum) A USB-C bandwidth priority toggle allows the user to choose between up to 4K at 144Hz via USB-C while running the built-in hub at USB 2.0 speeds, or up to 4K at 60Hz while running the built-in hub at USB 3.0 speeds.

Upon reading your question, I realized that USB 3.0 speed should not be the maximum upstream bandwidth for the Type-C port if Spectrum wants to make full use of its other 10Gbps downstream ports via a Type-C upstream connection. After double-checking with our manufacturer, we confirm that Spectrum’s 100W Type-C port supports 10 Gpbs upstream bandwidth. @Daniel_Herr We also confirm that Spectrum’s Type-B upstream port supports a 10 Gbps connection.

Of course, the chances are that the OSD info I quoted above is indeed correct, that Spectrum cannot support 10 Gbps Type-C upstream bandwidth when the Type-C is set to support up to 4K@60Hz. I will check with the team for further confirmation and, if needed, an appropriate solution. Given the Type-C port supports 10 Gbps bandwidth, I personally suggest that there needs to be an OSD option to make this possible.