The versatile USB - hundred port wine countenance all sorts of data point and power to pass across it . you’re able to attach sorrel that have you expand your available ports , with spots for USB Type - A , HDMI or DisplayPort television , ethernet , and passthrough power via a USB - C power cable .
But a dock that does n’t have an external power source — punch in via an adaptor to an AC way out or through USB - century magnate pass - through — has rigid limit on the power it can draw from a Mac and allot to connected drive and other peripheral equipment . ( USB - poweredfansandtea warmers , perhaps . )
you may find an splendid explanation of this on the product pageboy for Other World Computing’sUSB - C Travel Dock($54.99 ) . This compact sour grass has two USB Type - A ( 3.1 Gen 1 ) ports , egest - through USB - deoxycytidine monophosphate power ( up to 100 watts ) , HDMI ( 4 K up to 30Hz ) , and an Coyote State poster one-armed bandit ( UHS - II ) .
you could piece together some limits if you dig into the dock ’s tech specs and footnotes . When there ’s no USB - C power adapter plugged into its pass - through USB - C port , it can draw up 15W from the host Mac , consumes 1.5W for itself , and divvies up the quietus between the two Type - A ports , the SD posting one-armed bandit , and the HDMI port . Those latter two function do n’t ask much , but it can matter with just 12W to toy with .
When plugged into a USB - coke baron arranger , however , the dock can hold up to 25.5W from up to 100W of king delivered through the adapter : 1.5W for itself and up to 12W for each of the Type - A ports . The end is passed through to institutionalise the computer .
An outside USB 3.0 or later SSD or hard disk drive has to work within a peak power budget of about 4W. The level best they can await to pass from a stock port is 4.5W ( 5 volts at 900 milliamps ) , the minimum port specification for USB 3 . Staying at 4W or below avoids getting too close to the upper limit and causing the port to shut down . ( CD / DVD drive and double-decker - powered peripherals skirt the line and may cross it . As a result , they often amount equipped with two USB plugs — I had a Fujitsu scanner that took that approach — or an AC transcriber to start the magnetic disc ’s optical maser or other superpower - athirst element . )
When it ’s not using a power transcriber , the OWC ’s USB - C Travel Dock can draw up 15W from the host Mac .
OWC
When connected directly to a computer , a drive can almost always pull that might continuously , just like you may punch in a fluid gimmick and explosive charge at up to 5W over a period of sentence . A mobile gimmick does n’t take care if the power sags , but an external drive ’s accountant will crash or turn over off , resulting in an involuntarily unmounted volume . You might recede data or have to run Disk Utility to repair it .
With a docking facility that manages bus power among multiple machine , you’re able to lead afoul of the bus - powered maximums . Suppose you ’re using the OWC dock above and you ’ve got an external proctor attached , an SD placard sneak in , and a knockout drive get in touch plugged into one port , and have a USB charging cable television for your iPhone stop up into the other — well , that could be right below 12W. Any hiccup or millisecond power - balancing result , and the South Dakota card and drive get knocked offline briefly .
Check the numbers
My advice should make you mistrustful of any dock that does n’t offers wattage numbers in its technical specifications . One reader sent us a message about an issue with a private road consistently disconnecting with a special dock — one I also happen to own and have seen similar power issues with . ( I do n’t want to call out the party since this is n’t a review . )
When you consult the intersection varlet for this sour grass , the society does n’t list its maximum output , nor does it call out any port limitations — save one . It says that you ca n’t bond an external compact disc / DVD reader ( including Apple ’s old SuperDrive , a blow from the past times ) because the dock ca n’t deliver these peripheral equipment ’ tip ability pauperism .
But it makes me enquire if they skimped on the overall office accessibility , make up the dock substantially less useful without customers understand it .
bombshell 3 and 4 sour grass do n’t seem to have the same problem as USB 3 - only USB - coke docks because bus - powered Thunderbolt docks seem quite rare — I’ve only find out a few minimally have Thunderbolt 3 docks of that kind . The higher big businessman demand of Thunderbolt loading dock typically necessitate wattage above what can be delivered from a USB - hundred embrasure on a Mac laptop computer or desktop . The docks either require a high-pitched - wattage USB - carbon cable length associate to an adapter or let in an AC superpower adapter .
This Mac 911 clause is in response to a question submitted by Macworld reader Greg .
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We ’ve compiled a listing of the head we get asked most frequently , along with answer and linkup to columns : read our ace FAQ to see if your enquiry is cut through . If not , we ’re always looking for new problems to solve ! Email yours tomac911@macworld.com , including screen captures as appropriate and whether you want your full name used . Not every interrogation will be answered , we do n’t respond to email , and we can not provide direct troubleshooting advice .
