As you've never reached 100Mb, it's quite likely that the PC and/or ethernet cable can only support 100Mbps. This will give a maximum speed of about 90Mb.
Have a look on your Superhub where the ethernet cable is conected, is the light yellow or green? Yellow means it is being limited to 100Mb by the cable or PC.
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Some great advice there from cje85. Let us know how it goes!
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