Question: Can the Pegasus R4i be used in the 2023 Mac Pro

Answer: Unfortunately, no.

While the new Mac Pro does have PCI slots, it lacks the MPX slots of the 2019 Mac Pro. The MPX slots supply additional power to the PCI cards installed and the MPX slots were designed for the Pegasus R4i and the Video cards used by the 2019 Mac Pro. Without the MPX slots, neither the Pegasus R4i nor the Video cards used in the 2019 Mac Pro can be used.