The RX3i PACSystem is Emerson’s evolutionary upgrade from the 90‑30 line. It retains backward compatibility with existing 90‑30 I/O and racks but adds PCI‑based backplanes and a family of high‑speed CPUs with embedded Ethernet. This makes migration straightforward, yet the platform still straddles two backplane technologies and requires GE’s Proficy software. It’s a practical interim step for sites with installed 90‑30 hardware, but new installations might skip the half‑measures and adopt fully integrated PAC architectures that don’t carry the baggage of two decades of design decisions.