There's been several versions of the CX600 ... both had twin 8 pin (6+2) cables
(75-001668 / CP-9020048) Discontinued - OEM = CWT - (2) 8-pin cables
(75-002018 / CP-9020060) Discontinued - OEM = CWT - (2) 8-pin cables
There are also several versions of the EVGA 970 but none needs more than (2) 8-pin cables
04G-P4-2974-KR needs (2) 6-pin
04G-P4-2972-KR needs (2) 6-pin
04G-P4-1972-KR needs (2) 6-pin
04G-P4-2978-KR needs (2) 6-pin
04G-P4-0974-KR needs (2) 6-pin
04G-P4-2977-KR needs (2) 6-pin
04G-P4-3975-KR needs 8 + 6 pin
04G-P4-3973-KR needs 8 + 6 pin
04G-P4-3978-KR needs 8 + 6 pin