Back to Basics: How Mainframes Work & Their Future

Mainframes carry a stigma of being old technology, but they’re actually more relevant than ever.

Today, mainframes are responsible for anything from checking in airline passengers to approving your purchase at the grocery store. Mainframes provide the e-commerce and mobile world a reliable, available, and scalable way to perform their most basic business functions.

Before we dive in, let’s define some important terms:

  • Central Processor (CPU): The main brain in charge of processing data and moving it to the correct input/output processor.
  • System Assistance Processor (SAP): Smaller processors that help move data around as quickly as possible to the processor with the correct input/output programing.
  • Architecture: The programing engineered into a processor that details its main function (moving data, storing data, performing client statistics, processing bulk information, computing data, etc).
  • Input/Outputs (I/Os): Smaller CPUs built with specific architecture to take in an input and rapidly compute an output. These are stored in the I/O Cage of the mainframe.

How Mainframes Work

Mainframes have been running in the background for decades supporting conveniences such as ATMs, accurate bank statements, online and in-store transactions, and many other daily processes. But how do they do this?

Mainframes process large amounts of small data rapidly using CPUs, SAPs and I/Os:

  1. When a request for information is filled (i.e. a flight attendant searching a reservation) it gets sent to a mainframe.
  2. The main CPU sends the request to additional processors (SAPs) to move data to the correct I/O processor cards.
  3. The I/O’s then rapidly compute the output based on their specific role (i.e. a passenger’s reservation info).
  4. Finally, the output is transferred back out to the original request source (i.e. the attendant instantly receives the passenger’s flight reservation information on the computer monitor).

Engineers must configure and reconfigure these I/Os to meet unique project requirements that are often critical to a business and too large to be computed internally like:

  • Customer order processing
  • Financial transactions
  • Production and inventory control
  • Payroll
  • Bulk client information storage

Modern mainframes house advanced I/O cards with upgraded architecture to process modern mobile app information, security — you name it.

Mainframe Computer Advantages & Characteristics

Mainframes are built to provide reliability, availability, and scalability through processing. Their capacity to handle millions of transactions of data with 100% accuracy and little to no downtime is an unavoidable need for many companies.

Imagine if an airline couldn’t find your reservation or your bank miscounted your finances — you’d be filing a complaint quickly. These issues are prevented by mainframes accurately computing and transferring data in real-time.


  • Modern architecture provides the ability to share data among other I/O systems with dynamic capabilities for upgrading both hardware (CPUs & SAPs) and software (I/Os).
  • Mainframes are unique because their advanced I/O clustering technologies allow them to retain performance levels when upgrading computing functions, memory, or storage. This means no crashes and no downtime.


  • Modern mainframes can take on upwards of billions of transactions accurately and in real-time while storing more data.
  • Mainframes have complex self-checking and self-recovery features. They work in milliseconds to locate and fix errors by making quick updates or notifying the proper engineers.


  • Divide data: mainframes can add memory, storage and processors without missing a beat. This is because mainframes can divide data into multiple independent and isolated machines, each running on its own operating system. Ideal for information storage, back up and security.
  • Compile data: Moving from many smaller processors and servers to a few large mainframes is a simple way companies can expand their capacity to take on more information and increase their processing power. Ideal for growing companies.

The Future of Mainframe Computers

Mainframes have come a long way since their introduction to the world in 1952. As a dominant leader in the industry, IBM continues to adapt and enhance their architecture to handle IT needs in the cloud and mobile e-commerce era. In the 1990s IBM expanded functions by adding tiers of data processing capabilities like web-serving, autonomics, disaster recovery and grid computing.

zSystems mainframes meet the needs of businesses and organizations that continually rely on this technology to power their most necessary tasks.

For that reason, they remain first choice in the airline, banking, healthcare and insurance industries as well as the government.

Top Gun supplies refurbished IT hardware — including the Z systems — to enterprise companies in need of cost-effective short or long-term solutions.