Hardware Comparison: GE Fanuc Series 90-30 vs the Emerson GE RX3i

The GE Fanuc Series 90-30 has long been a workhorse PLC for GE automation control systems. Introduced in 1991, the 90-30 series has been a popular choice for industrial control professionals because of its versatility and modularity.

By contrast, the RX3i CPU Programmable Automation Controller by GE Automation represents the move toward a more comprehensive view of automation and one that both builds on the foundation laid by the 90-30 series while offering even more advanced features and versatility.

GE 90-30 Series General Specifications and Features

That the 90-30 series lasted for the better part of 30 years is a testament to its popularity. By offering a platform that addressed space concerns as well as cost effectiveness, the 90-30 has been known for ease of programming and their ability to be operated through a variety of inputs.

The versatility of the 90-30 series is due to its large variety of CPUs, and each of the 11 available CPUs can accept multiple expansion modules for additional features. These CPUs range from standard entry level CPUs, mid-range models and high-end performers.


Standard Models include the CPU 311, CPU 313 and the CPU 323. The 311 and 313 offer 160 discrete I/O and 5 I/O module slots, while the 323 allows up to 320 discrete I/O and 10 expansion I/O slots. All three models offer 64 In/32 Out analog capability.

These standard models have the CPU built into the backplane, making all onboard slots capable of accepting I/O. They also accept EtherNet and various bus protocol modules and use Ladder Logic and SFC for their programming language. While the 311 only has 6K bytes of memory, the 313 and 323 each have 12. All three standard models have a single serial port.

Midrange models consist of the CPU331 and the CPU341. They offer increased functionality over the entry level models that include features such as override capability, and a real time clock with battery backup. Both he 331 and 341 offer 1024 discrete I/O, a considerable jump compared the entry models.

Both mid-range models offer 49 I/O expansion slots and a single serial port. But the biggest jump between these two models is in the analog capability. The 331 allows 128 In/64 Out while the 341 jumps to a high of 1024 In/256 Out.

Coming in on the high end are the CPU350, CPU351, CPU352, CPU360, CPU363 and CPU 364. These high-performance CPUs achieve much higher throughput by using an Intel 386EX processor. They can handle a much higher level of I/O and can use either Ladder Logic, SFC or “C”.

All high-end models allow 4096 discrete I/Os and all have analog capability of 2048 In/512Out. All high-end models have 80K bytes of user logic memory except for the 364 which has 246K. The same is true for the number of serial ports with each model having 3, again the exception being the 364 which has 1 RS485 port, 1 EtherNet port and 1 TCP/IP port built in.

The 90-30 series CPUs are capable of being accessed over the internet can be attached to an EtherNet LAN and they were designed to operate with a variety of third-party devices as well as HMIs and motion controls. All models have:

  • PID functionality to control temperature, flow, pressure and other process related factors
  • Four level password security to protect the physical, logic and application security
  • Complete diagnostics for both the CPU and I/Os
  • Capability to change programming online


The popularity of the 90-30 has always been in its flexible and versatile modularity. With over 100 I/O modules and specialty modules for communication, the 90-30 series allows for the buildout of a complete automation control system. This includes a wide range of both discrete and analogs as well as specialty modules.

The 90-30 series allows a large variety of communication capabilities through use of its Genius Bus Controller. This I/O controller allows peer-to-peer messaging and communication modules that can be added include:

  • World FIP
  • Profibus
  • Interbus
  • Lonworks
  • DeviceNet
  • SDS
  • Modbus RTU

It can also accept a wide range of specialty modules including:

  • Digital high-speed counter
  • SPC Coprocessors
  • Modems
  • Stepper positioning

Unlike many control systems, the GE 90-30 series was not designed as a “base” system with some modular capacity to add functionality. Rather, the 90-30 series was completely modular. By selecting the right combination of components from the ground up, automation professionals could design an infrastructure that could be customized to meet almost any level of control needs. It was also cost-effective, easy to install, easy to configure and easy to program.

RX3i PAC System General Specifications and Features

With many controllers, changing them out at end of life out requires a complicated migration that often includes new software, new firmware, and other integration differences. They may also include mechanical issues like mounting options, incompatibility with existing enclosures and other headaches. But while the RX3i was designed to add functionality and capacity compared to the 90-30 series, it does so without disrupting the existing system and can be done incrementally and on the fly to prevent shutdown. The RX3i series line includes:

  • CPE100
  • CPE115
  • CPE302
  • CPE305
  • CPU310
  • CPU315
  • CPE305
  • CPE310
  • CPE330
  • CPE400
  • CPL410

Common Features for RX3i CPUs

All RX3i units have several common features across the series. Common features include:

  • Configurable data
  • Embedded Serial and EtherNet Communication
  • Configurable program memory
  • Capability to program in Ladder, Function Block, Structured Text and “C”.
  • Up to 512 program blocks
  • Online editing
  • Upgradable firmware

The RX3i system CPUs are less split among entry, mid-range and high end as they are split by their embedded communication capabilities. This is due to their designed purpose for IIoT applications and a completely connected factory where connectivity and data collection are paramount in the system.

The CPE100 and CPE115 are standalone CPU sand both have an EtherNet/PROFINET interface. The 100 has slightly lower user memory at 1.0 MB while the 115 has 1.5 MB. They can both be used as a standalone control system or as an auxiliary control system for another CPU. They four EtherNet Ports as well as an embedded RS-232 serial port.

In addition to PROFINET, the 100 and 115 can support other communication protocols as well including Modbus TCP/IP, EGD, SRTP Client/Server and others. They can also utilize Modbus/RTU and Serial I/O for serial communication.

The CPE302, CPU305 and CPU310 have less user memory than the rest of the series with the 302 coming in at 2MB, the 305 with 5 MB and the 310 with 10 MB. For I/O, the 302 allows 16KB of discrete I/O while the 305 and 310 allows 32 KB. All three units allows 32KB words for analog I/O and all three allow 8 simplex remote I/O devices. Each model also has a USB interface and a single serial port. And each support a large variety of EtherNet protocols as well as both ASCII serial and Modbus RTU serial protocols.

There is a considerable jump in user memory in the CPE330 which allows 64MB. However, the 330 uses 32 KB of discrete I/O and 32KB of words for analog I/O, same as the 310. The 330 also has considerably higher capacity for remote I/O devices compared to the 302, 305 and 310. The 330 supports 64 simplex and 64 redundant remote I/O devices overall. It supports the same serial communications of ASCII Serial and Modbus/RTU and all the same EtherNet protocols.

Just as the CPE100 and CPE115 are standalone small profile, small architecture units, the CPE400 and CPL410 are larger, more robust standalone units. The only distinction between the CPE400 and the CPL410 is that the CPL is designed for use with the Linux operating system. All other specifications are the same. Both unit’s user memory comparable to the 330 at 64MB and their discrete and analog I/O are the same as the 330 at 32 KB of discrete I/O and 32KB of words for analog.

The 400 and 410 have three EtherNet ports, however, two of them are switched ports. They also have less remote I/O capacity compared to the 330. The 400 and 410 have 32 simplex and 20 redundant remote I/O capacity.


Just like the 90-30 series, the RX3i series was designed with modularity as its core. In fact, the RX3i was designed as a direct replacement. Because of this, the backplane for the RX3i has the same mounting and hole positions. Additionally, 90-30 PLCs can be used directly with the RX3i system and 90-30 blocks can be installed into the RX3i rack.

This interoperability gives the RX3i tremendous advantages as an upgrade and replacement. For one, it means that upgrades and replacements of components can be done incrementally as needed. However, if automation engineers wish to fully replace an entire 90-30 series system, they can do so on-the-fly, with a minimum of time and without shutting the system down.

Benefits of the RX3i

There are many benefits of the RX3i system over the 90-30. These include:

  • IIoT – As mentioned, the RX3i was designed to allow companies to utilize IIoT capability within their automation system. This is one of the key differences between legacy systems such as the 90-30 and the RX3i. With the RX3i, the automation control system can be enabled for IIoT by devices such as GE’s IICS, a big distinction between the two series capabilities.
  • Cost – Another benefit is in total system cost. Because the hardware and components for the RX3i mount directly into and alongside 90-300, an upgrade can be phased in over time to avoid higher upfront costs. This cost saving can also be realized in connecting to IIoT with GE’s Predix Cloud feature.
  • Real-Time Communication – The use of PROFINET over standard EtherNet is an advantage for RX3i as well. Standard EtherNet cannot realize real-time performance. By using the RX3i, built in PROFINET adaptors allow wireless and wired communications in real-time to a network.
  • Scalability – While the 90-30 was a popular system with a large feature set and flexible applications, the RX3i explodes the I/O scalability to allow up to 32KB of I/O per controller. This is vastly larger than the 90-30 series and is required to allow enablement of IIoT and modern data monitoring for the connected factory.

Limitations of the 90-30 Series Compared to RX3i

Despite their high degree of interchangeability, there are some limitations that are revealed by comparison. For one, the RX3i is RoHS compliant compared to the 90-30 series. This and other regulatory and compliance issues mean that upgraded systems must replace with a higher standard or phase out earlier than their actual end of life cycle (depending on the governing entity’s requirements). This makes the interchangeability even more important and cost effective because 90-30 series users have a direct replacement.

Interchangeability is a popular feature of the RX3i and 90-30 series systems. In addition to dozens of modules for the RX3i, there are over 60 90-30 modules that are directly pluggable for use in the RX3i rack. However, not all the older 90-30 modules can be used in conjunction with the RX3i. There are over 50 modules from the 90-30 series that cannot be used together. As an example, these prohibited modules include (but are not limited to):

  • Several programmable coprocessor modules
  • 10 24V DC modules
  • The Complicity System and Complicity modules
  • Communication control module
  • Genius Bus module
  • 90-30 bus interface
  • And others

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