Measure what each USB port on your machine actually delivers

short · 40 min · Objective 3.2

Task

Survey your own ports for speed and power, using measurement and documentation rather than the colour of the plastic, and record the negotiated wattage where the system reports it.

Steps

  1. Record every USB port in lab/usb/ports.csv with header port_id,connector,colour,claimed_speed,measured_speed,source.
  2. Measure each port with the same known-good fast cable and the same storage device, copying a file of at least 500 MB and recording the rate in MB/s.
  3. Record charging behaviour in lab/usb/power.csv with header port_id,charges,negotiated_watts,how_determined for whatever devices you can attach.
  4. Write lab/usb/mismatch.md naming every port whose colour or assumed speed differed from what you measured, and what the correct source of truth was.
  5. Write lab/usb/capability.csv with header port_id,data,power,video,thunderbolt,evidence for any USB-C ports, filling evidence from the manufacturer's specification.

Verify

awk -F, 'NR>1 && NF>=6 {n++} END {print n" port(s) surveyed"}' lab/usb/ports.csv
awk -F, 'NR>1 {print $5}' lab/usb/ports.csv | sort -u | wc -l
awk -F, 'NR>1 && NF>=4 {n++} END {print n" power observation(s)"}' lab/usb/power.csv
grep -c . lab/usb/mismatch.md
awk -F, 'NR>1 && $6!="" {n++} END {print n+0" USB-C port(s) with evidence"}' lab/usb/capability.csv

Two or more ports surveyed, at least two distinct measured speeds where the machine has ports of different generations, power observations recorded, and the mismatch note present. A survey where every port measured identically on a machine with mixed ports suggests the cable was the limit, not the ports.

Notes

Use the SAME cable and the SAME device for every port, or you are measuring three variables at once. That is the control that makes the comparison mean something.

This is an independent study companion for CompTIA A+ Core 1 220-1201 and is not produced by or endorsed by CompTIA.