USBefuddled: Untangling the Rat’s Nest of USB-C Standards and Cables
Some of this wrong, some of this is way too wordy.<p>&gt; 
USB-C cables that support Power Delivery 2.0 and 3.0 can carry a minimum of 7.5 watts (1.5 amps at 5 volts) or 15W (3A at 5V), depending on the device, cable, and purpose.<p>Nope, all USB C cables are 60W minimum. The connector might support less, but the cables do support 60W minimum.<p>&gt; USB-C Charge Cable—designed in the early days of USB-C<p>Nope, nothing wrong with a USB C cable which doesn&#x27;t have the high speed lanes connected. That&#x27;s a perfectly specification conformant cable. High speed lanes is the phrase I miss from this too long article.<p>Here&#x27;s a much shorter explanation of it all.<p>A USB C cable always have separate wires for 1) power , either 60W or 100W capable. The latter needs an eMarker IC in the connector 2) a separate pair for 0.48Mbit&#x2F;s speed USB data (aka USB 2.0) 3) it can have and most do have four high speed lanes (each lane is formed from two wires as differential pairs). These lanes can carry various data , by default it will use two lanes to carry USB data -- at at least 5gbps, if the cable is short enough then 10gbps. (While 20gbps mode over four lanes is defined so few hosts support this we don&#x27;t need to care.) There are alternative modes besides USB, namely DisplayPort and Thunderbolt. In DisplayPort alternate mode it can use 2 or 4 lanes for DisplayPort. If two then the other two can be used for USB data as above. DisplayPort has its own versions: DisplayPort 1.2 can deliver 8.64 Gbit&#x2F;s video data over two lanes, while 1.3&#x2F;1.4 can carry 12.96 Gbit&#x2F;s and for both double that over four lanes. (DisplayPort 1.4 introduces compression as well which needs to be supported by the monitor and it&#x27;s very rare to do so.) This is aggregate video bandwidth for PCs: they can drive multiple monitors using a DisplayPort technology called MST. For Mac, you need Thunderbolt.<p>Thunderbolt. Unlike the previous ones where the cable is functioning the same as a pre-USB C cable and a simple (basically, passive converter) can dole out USB and DisplayPort data this one is a complex bus and both ends needs to have a Thunderbolt controller. The Thunderbolt 3 bus can carry PCI Express and DisplayPort data (USB is provided by the controller presenting a hot plug root hub, due to hot plug nature there&#x27;s a bevy of problems), the Thunderbolt 4 bus can carry PCI Express and DisplayPort and USB data. (Footnote: Thunderbolt 4 is the same as USB 4 with some optional features made mandatory. It is somewhat unlikely we will see non-TB4 USB 4 controllers so this is mostly just pedantry -- you can treat USB 4 and TB4 as being the same.) The bus bandwidth in one direction depending on cable length can be 20gbps or 40gbps. When allocating this bandwidth, DisplayPort has priority. How much DisplayPort is on the bus in total is a bit confusing due to some history: laptops with one Thunderbolt port most often will only put one DisplayPort 1.2 connection on the bus. Laptops with two ports always have full Thunderbolt and will put two DisplayPort connection on the bus (very rarely, single port laptops will do this too, mostly early workstations). This confusion goes away in Thunderbolt 4, that&#x27;s always full. But the bus is never faster than 40gbps so even if it is fed by two DP 1.3&#x2F;1.4 connections, it still can&#x27;t deliver more than 40gbps data where two independent DisplayPort cables would be able to deliver slightly more than 50gpbs.<p>Finally, power. If only 5V is required, resistors are used to signal how much power is requested. For 9&#x2F;15&#x2F;20V power is negotiated: the devices figure out which one is source and which one is sink, once that&#x27;s done, the source will communicate how much power it is able to provide. At most 3A can be used normally, at 20V provided the right cable is present, 5A is also a possibility. There is a separate wire for this communication. Using the same communication process, the data roles are decided: one of them will be upstream (think host) one of them will be downstream (think peripheral). There&#x27;s a sensible default where the upstream data role takes on the source power role  but this can be changed using this negotiation.<p>Footnote: these were fixed power. Today some devices support the PPS (Programmable Power Supplies) feature which allows the sink to rapidly change the wattage as needed. This also requires eMarker cables.<p>And yes, cables are a mess. <a href="https:&#x2F;&#x2F;people.kernel.org&#x2F;bleung&#x2F;how-many-kinds-of-usb-c-to-usb-c-cables-are-there" rel="nofollow">https:&#x2F;&#x2F;people.kernel.org&#x2F;bleung&#x2F;how-many-kinds-of-usb-c-to-...</a>