The 997 can be linked to both 898c SI models with the discontinued AS INTERLINK accessory.
They would only share waypoints and a GPS antenna.
INTERLINK was discontinued and no longer supported when the XX9 models came out.
The 898's supports Ethernet also.
Humminbird Helix 12 CHIRP SI, 1198c SI, 1198c SI, ONIX 10 SI NT, Helix 7 CHIRP SI GPS G2, SOLIX 12 SI, 360, RC-1