Answer: Compare LnkSta speed and width with LnkCap for the same PCIe function. A lower value can reflect idle power management, slot wiring, the immediate partner or firmware policy. Capture both link ends under the same workload and compare the expected configuration before calling it degraded. This checker interprets supplied text and does not test hardware.
One PCI function per box. Partner selection and capture timing remain user declarations. Samples are synthetic and labelled; they are not hardware captures.
Collect the same fields at both ends
lspci -t
sudo lspci -vv -s 01:00.0
# Repeat for the immediate partner you identified; compare the same workload.Keep the complete PCIe capability section: LnkCap2 and LnkSta2 describe different fields and are not substitutes for LnkCap and LnkSta. A width or speed limit is not enough to identify a defective component.
Read the link training, speed and width guide, decode raw bytes with the config decoder, or compare captures in the Console.
Sources and scope
Updated . All interpretation runs locally on supplied text. No electrical measurement, bandwidth test or link-training history is available here.
Questions
- Is a lower PCIe speed always a problem?
- No. A device can reduce speed while idle, and the link is also limited by its partner, slot wiring and firmware. Compare both ends under the same workload and against the expected board configuration. A single snapshot cannot establish a fault or its cause.
- Does an x16 card in an x8 slot count as degraded?
- The device may advertise x16 while the slot is deliberately wired for x8. The comparison shows the difference; platform documentation establishes whether it is expected. Physical slot length does not establish electrical lane count.
- Which function should I paste as the partner?
- Use the immediate upstream or downstream port at the other end of this physical link, not an arbitrary ancestor. lspci -t and the Linux sysfs parent path can help identify it. The page cannot independently verify which port you selected.
- Does this measure bandwidth or read hardware?
- No. It interprets text already collected with lspci. GT/s is the transfer rate per lane, not measured application throughput. Missing fields remain unknown and no command, reset or hardware write runs in the browser.