What is the Difference Between Mainframe, iSeries, and AS/400?

What is the Difference Between Mainframe, iSeries, and AS/400?
5 min read

Amidst the ever-shifting panorama of corporate computation, grasping the subtleties that distinguish diverse technologies emerges as a pivotal factor in engendering well-informed determinations. The duo of paramount technologies that have fundamentally molded this domain encompass the venerable mainframe architecture and the iSeries innovation, alternatively recognized as the IBM Power Systems. However, to fully grasp the intricacies, it's essential to also explore the predecessor of the iSeries - the AS400. In this comprehensive article, we will delve into the differences between mainframes, iSeries, and the AS/400, shedding light on their architectures, capabilities, and use cases.

Mainframe Computing:

Reliability and Performance Redefined Mainframes have long been the stalwarts of enterprise computing, epitomizing reliability, scalability, and robustness. These machines are designed to handle massive workloads and ensure uninterrupted operations for critical applications. Mainframes are the workhorses behind industries like finance, healthcare, and government, where data processing and security are paramount.

Architecture and Capabilities

Mainframes boast an architecture built for exceptional processing power, extensive memory capacity, and unmatched I/O capabilities. The central processing unit (CPU) within a mainframe is optimized for executing complex instructions efficiently, allowing seamless multitasking and optimal resource utilization even under heavy workloads.

The capabilities of mainframes extend beyond their processing power. They excel at transaction processing, batch processing, and supporting mission-critical applications. With features like advanced security mechanisms, redundancy, and fault tolerance, mainframes ensure data integrity and minimize downtime, making them indispensable for industries where uninterrupted performance is non-negotiable.

iSeries (IBM Power Systems):

Flexibility and Modernity Converged The IBM iSeries, known as IBM Power Systems, presents a modern twist to enterprise computing, marrying the power of a mainframe with the flexibility of a distributed system. This amalgamation caters to businesses with varying requirements, from data analytics to cloud integration.

Architecture and Capabilities:

The architecture of the iSeries revolves around providing a unified platform for diverse workloads. Unlike the monolithic structure of traditional mainframes, iSeries systems allow the concurrent operation of multiple operating systems. This adaptability empowers organizations to streamline their IT infrastructure and operations, resulting in cost savings and simplified management.

The agility of iSeries systems is a hallmark feature. They excel at handling mixed workloads, making them an ideal choice for organizations that need to run a range of applications such as databases, web servers, and virtualized environments. Embracing modern technologies like cloud integration and virtualization, iSeries systems enable businesses to stay aligned with evolving IT trends.

AS/400: The Precursor to iSeries:

To fully understand the evolution of the iSeries, it's essential to acknowledge its precursor, the AS/400. The AS/400 was a midrange computer system introduced by IBM in 1988. It offered a groundbreaking approach to computing by integrating hardware, software, and storage into a cohesive system.

Architecture and Capabilities:

The AS/400 framework heralded a revolutionary era in its heyday, touting a singular-tier memory structure that streamlined programming and oversight. Its distinct object-centric framework facilitated the harmonious amalgamation of applications and data. The software milieu of AS400, denoted as OS/400, furnished an exhaustive array of tools encompassing development, database governance, and system stewardship.

The prowess of AS/400 extended to encompass a wide spectrum of applications, spanning from corporate operations to decision-bolstering systems. Its unified essence, coupled with resilient security attributes, rendered it an enticing preference for entities in quest of an all-encompassing solution.

Use Cases and Scenarios:

Understanding the distinctive characteristics of mainframes, iSeries, and the AS/400 is pivotal for selecting the right technology for specific scenarios.

Mainframe Use Cases:

Mainframes excel in scenarios demanding massive data processing, reliability, and security. Industries handling sensitive financial data, healthcare records, and extensive transaction processing rely on mainframes to ensure uninterrupted operations and data integrity. Their ability to handle substantial workloads with minimal downtime renders them invaluable for applications requiring 24/7 availability.

iSeries Use Cases:

The iSeries' versatility suits businesses seeking a unified platform capable of handling diverse workloads. Organizations looking to consolidate their IT infrastructure, integrate cloud services, and harness virtualization can benefit from the flexibility of iSeries systems. These systems are particularly apt for dynamic environments that prioritize adaptability and rapid resource provisioning.

AS/400 Use Cases:

The AS/400's integrated architecture made it an appealing choice for businesses looking for a comprehensive solution. Its capabilities spanned applications like enterprise resource planning (ERP), customer relationship management (CRM), and database management. AS/400 found favor in small to midsize businesses seeking an integrated platform that streamlined operations and minimized complexity.


In the intricate tapestry of enterprise computing, distinguishing between mainframes, iSeries, and the AS400 is paramount. Mainframes embody reliability and performance, catering to industries necessitating steadfast data processing and security. On the other hand, iSeries introduces modernity and flexibility, catering to businesses seeking adaptability and consolidation. The AS/400, as the precursor to the iSeries, brought integration and simplicity to the forefront.

Choosing the right technology hinges on comprehending the unique requirements of an organization. Whether harnessing the raw power of a mainframe, embracing the adaptability of an iSeries, or appreciating the integrated approach of the AS/400, the decision shapes the technological foundation for years to come.

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abel willium 2
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