TMS320C6678: Hyperlink or SRIO which is better to link two DSP's together?

Hi Joe,

Both can be used. If you take a look you will see that both SRIO and Hyplnk examples have chip-to-chip use cases.
However hyperlink, as far as I know, hperlink is better for connecting two keystone devices, because it is an extension of the chip internal interconnect.
Have a look at the HyperLink user guide, section 1.1 Purpose of HyperLink:
"HyperLink provides a high-speed, low-latency, and low-pin-count communication interface that extends the internal CBA 3.x-based transactions between two KeyStone devices."

The RapidIO is slightly more often used for connecting to FPGA.

Best Regards,
Yordan