搵到原因...隻switch著o左"Link Short-Reach Energy Saving Mode "後會跌速，但Google後都唔明"Link Short-Reach Energy Saving Mode "係咩o黎...
雖然o係隻switch入面行cable test都會話cable open，但用部SSD notebook試，食得盡GE，即使用HDMI stacking都食得盡...
而RTFM咁寫:
Short-Reach Mode — Power usage is adjusted to the actual cable length.
In this mode, the VCT (Virtual Cable Tester) length test is performed to
measure cable length. If the cable is shorter than a predetermined length,
the switch reduces the power used to send frames over the cable, thus
saving energy. This mode is only supported on RJ45 ports.
Power savings and current power consumption in Short Reach mode can
be monitored. The total amount of saved energy can be viewed as a
percentage of the power that would have been consumed by the physical
interfaces had they not been running in Green Ethernet mode.
