# What is the difference between ControlLogix L8 and L9?

**URL:** <https://forumautomation.com/t/what-is-the-difference-between-controllogix-l8-and-l9/14023>\
**Category:** Allen Bradly\
**Tags:** interviewquestions\
**Created:** [April 17, 2026, 12:51pm UTC](https://forumautomation.com/t/what-is-the-difference-between-controllogix-l8-and-l9/14023 "2026-04-17T12:51:08Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Instrument\_Engineer](https://forumautomation.com/user_avatar/forumautomation.com/instrument_engineer/32/6734_2.png) [@Instrument\_Engineer](https://forumautomation.com/u/Instrument_Engineer)\
**Post date:** [April 17, 2026, 12:51pm UTC](https://forumautomation.com/t/what-is-the-difference-between-controllogix-l8-and-l9/14023/1 "2026-04-17T12:51:09Z")

</div>

**What is the difference between ControlLogix L8 and L9?**

 ![image](https://cdn.forumautomation.com/original/2X/2/201b4f8d6ae33d8d2742155baf106fc6471e8792.jpeg)

---

<div class="post-metadata">

**Author:** ![Sundar\_Iyalunaidu](https://forumautomation.com/user_avatar/forumautomation.com/sundar_iyalunaidu/32/7404_2.png) [@Sundar\_Iyalunaidu](https://forumautomation.com/u/Sundar_Iyalunaidu)\
**Post date:** [April 24, 2026, 2:16pm UTC](https://forumautomation.com/t/what-is-the-difference-between-controllogix-l8-and-l9/14023/2 "2026-04-24T14:16:40Z")

</div>

## What is the difference between ControlLogix L8 and L9

### Basic difference

L8 is part of the ControlLogix 5580 family, and L9 is part of the newer ControlLogix 5590 family. The L8 platform is built for high-performance control and has a 1-gigabit integrated Ethernet connector and up to 45% more capacity than older models. The L9 platform goes even farther by adding more memory for users, faster scan times, better communication, and built-in safety features.

### Hardware and capacity

From the perspective of a plant engineer, the L9 family is designed for larger and more interconnected systems. Rockwell’s documentation say that L9 controllers have two built-in Ethernet connectors, a USB Type C interface, and memory options that go up to 80 MB standard and 12 MB safety on the higher variants. The 5580 family, on the other hand, has one built-in Ethernet port and is already set up for current I/O, motion, and safety applications, although it doesn’t have as much headroom as the 5590 line.

### How to choose in real projects

If the application is a normal upgrade, migration, or medium-sized process system and the current architecture is stable, use L8. If the project needs additional memory, better network connectivity, tighter safety integration, or a stronger platform for future growth, choose L9. L9 is frequently the preferable choice for plants that want to combine controllers, make panels less complicated, and support more demanding multidiscipline control.