R740xd only support connecting backplane to PERC controller not to integrated SATA connector. Below link have details on various backplane connectivity supported for R740xd [URL] 
Hi all, R740xd has an internal SATA controller with 2 SATA connectors. If we want to connect all drives to the internal connector what cables are needed?  I see the R740xd backplane has 2 double SFF-8643 miniSAS connectors but I dont finde the cables to connect it to the integrated SATA connectors.
R740xd with full SATA disks and internal SATA controller