TIA-EIA-568-B.1 pg21,ch 5.5.1指出cat 5在90m(两端空余5m以供链接端)可以提支持100Mhz
The length of category 5e multipair balanced 100-ohm backbone cabling, that supports data applications up to 100 MHz, should be limited to a total distance of 90 m (295 ft).
一般在短距离内,例如本次测试,125Mhz在Cat-5上也是能达到到的