I had a cable modem by 1998. Faster uplink speed than I have now, actually – saturated the 10MBps network in my house and it wasn't throttled in the pre-Napster, pre-port-filtered era.
10Mbs, not 100. With Cox in San Diego could hit (IIRC) 16 Mbps per cable segment but at the time no cable modem had a 100Mb ethernet interface since that hardware was still expensive.