Hi root_console

 

Yes the XR5610 service manual confirms that this conversion is supported at the cabling level. The manual explicitly documents both configurations for the same 4 × 2.5-inch backplane:

PERC configuration: CTRL_SRC_SA1 → BP_DST_SA1
Onboard SATA configuration: SL7_PCH_SA1 → BP_DST_SA1

 

1. SATA cable part number

I could not find a reliable Dell-published part number for the SL7_PCH_SA1 → BP_DST_SA1 cable in the publicly available XR5610 documentation.

The Dell manual identifies it only as “SATA cable connector with 4x 2.5-inch backplane” and provides the routing, but does not publish the spare-part number.
https://www.dell.com/support/manuals/en-us/poweredge-xr5610/pexr5610_ism_pub/cable-routing?guid=guid-673aa09e-5934-4d7a-ba8b-62a393656f93&lang=en-us&utm_source

The safest way to obtain the exact Dell spare is to have Dell Parts/Support identify it against the specific XR5610 Service Tag/configuration, since Dell's parts portal supports lookup by Service Tag or part number.
I would not recommend using a generic SATA cable unless the connector type, pinout, shielding, length and routing are confirmed to match the Dell cable.

2. Is the PERC-to-onboard SATA conversion technically supported?

Yes, the documentation strongly indicates that it is.

The fact that Dell provides a dedicated cable routing:

System board SL7_PCH_SA1 → Backplane BP_DST_SA1
means the 4-drive backplane is designed to operate from the onboard SATA controller, in addition to the PERC SAS configuration.

So the basic configuration would be:

Current:

PERC H355 → PERC SAS cable → 4x2.5" backplane

Proposed:

System-board SL7_PCH_SA1 → Dell SATA cable → 4x2.5" backplane

The backplane itself does not appear to need replacement based on the documented routing.