Start with one shared pool
A hub can expose several 5 or 10 Gbps ports while connecting upstream through one finite link. Add realistic simultaneous demand, not every device’s marketing ceiling. A keyboard may be negligible; two active SSD copies, capture video, and Ethernet may not be.
Useful separation
The Data Path Checker finds the ceiling of one device chain. The Shared Bandwidth Planner adds concurrent demand from several devices sharing one upstream pool.
The Data Path Checker finds the ceiling of one device chain. The Shared Bandwidth Planner adds concurrent demand from several devices sharing one upstream pool.
Why measured throughput varies
USB scheduling, protocol overhead, bursts, storage media, filesystem work, hub translation, firmware, and other clients on the same host controller all affect results. Microsoft notes that multiple client drivers compete for finite USB bandwidth and that exact available bandwidth can be difficult to predict. A USB 3 storage device behind a USB 2 hub also falls back to the slower path.
A controlled test order
- Confirm each device’s direct negotiated path before combining devices.
- Identify the hub’s upstream link, not just its downstream labels.
- Record the workload that must run simultaneously.
- Test one device, then add one load at a time.
- If all functions drop, also test power and the common upstream cable.
Sources
- Microsoft Learn: USB bandwidth allocationFinite controller bandwidth and competing clients.
- Microsoft Learn: USB FAQHub generation, fallback, and separate USB 2/SuperSpeed hub behavior.