what mainframe computer is and how it works
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Well, a mainframe computer was named for a pice of hardware that used to be used in telephone systems called a main frame. It’s sort of the ancestor of modern telecom and computer racks.
In the old days, we used the term mainframe to distinguish the ‘big iron’ computers from the smaller minicomputers and desktop microcomputers. Even in those days there was no one thing other than the physical size that you could point at and say “This is what makes this computer a mainframe.” The rule of thumb used to be…
If you can pick it up, it’s a micro.
If you can’t pick it up but you can tip it over, it’s a mini.
If you can’t budge it, it’s a mainframe.
Now a days? A mainframe is just a system made up of a whole lot of computers that aren’t all that different from the ones we have. I haven’t heard the term used professionally in, well, my entire career. They were more or less gone by the time I showed up. Minis were even pretty rare and generally pretty old.
Lets say in your job there are occasionally really hard math problems that need to be solved. So the company has someone really good at math sit by your desk and solve the problems when they come up. But people who can solve really hard math problems are hard to find and get paid a lot. Since the problems only come up occasionally, the math person isn’t doing much most of the time.
So your company decides that instead of having a math person at every desk, they will set up a room full of math people. Instead of having your problems solved at your desk, you will send them to the math room where they will be assigned to someone to solve. Since multiple people can use the same person they need less math people and the ones they have will be working most of the time. Plus, when you have a really really hard problem multiple people can work on it together.
That is basically what a mainframe is. A computer designed to handle a large amount of operations as quickly as possible for things like data and transaction processing.
Fun fact, the current computing infrastructure of large VMware servers are in fact mainframes all over again.
Imagine your desktop computer was all your company / school could afford to buy.
Now imagine that you could get really long wires for the keyboard and screen.
Now imagine you could plug two keyboards and two screens in, but have those in different rooms.
Two people could use the same computer at the same time.
It’s that.
What are some examples of IBM Z in use today? IBM Z is used by 44 of the top 50 banks and all top 10 insurers worldwide, as well as a large number of government, healthcare, airline, and retail organizations and other companies that require the highest standards for performance, security, reliability, and availability.
IBM zSystems has its own architecture which is designed to work with huge caches, and it has instruction sets to handle enterprise workloads by using IBM’s own S/390x chip architecture. The S/390x architecture is supported by several popular Linux operating systems including SUSE, Red Hat, and Ubuntu, as well as a large number of open source applications.
IBM zSystems runs operating systems including z/OS, z/VM, z/VSE, z/TPF, and Linux. In fact, it is common for multiple operating systems to run on a single mainframe. LinuxONE is an IBM zSystems system that’s specifically dedicated to running Linux; this combines the benefits of the Linux OS with the capabilities and strengths of the mainframe like outstanding data security, availability, performance, efficiency, and cost savings.
At my job we have a bunch of machines producing goods that inspectors pick off the machines and package. Each machine has a windows computer at the end the inspectors use to log what they took and the quality of the product.
Now we have a lot of these computers; it’d cost a lot of money to buy a windows image for every computer so instead we have one large linux computer with UNGODLY amount of resources running virtual instances (virtual machines) of the windows os and then sending the gui to the machine terminals.
To answer the question, the computer with ungodly resources simulating other computers and passing the screen to another machine is the mainframe.
In the early 80s a mainframe was a computer that had a CPU that wouldn’t fit in a single cabinet (processor, memory, and input/output were often separate), a minicomputer fit the CPU in one cabinet, and a microcomputer fit everything in one cabinet.
The important part of Mainframe is the word “frame”. Back in the day when a large computer would have a room dedicated to it, the “frame” was what was inside the cabinets and was used to attach storage and other other peripherals. Think of a classical computer room from the 60’s and 70’s.
As computers got smaller and more powerful, the term drifted to simply mean a large scale, powerful computer. Typically with a lot of storage and usually located in a different place than the users.
Weirdly, mainframe computers were not necessarily “faster” than smaller computers, but they typically were designed to input/output large amounts of data and had a lot of storage. They would process transactions for banks, insurance companies etc. The computation is easy, but the amount of data moved was quite large.
They were the first broadly used machines to handle I/O in hardware. Smaller computers might have used software to manage network data, disk I/O, etc. A mainframe would have external hardware to handle that data being moved, freeing the computer to only have to do the actual computation. This allowed a mainframe to outperform a smaller computer of similar CPU power, by 10x or more.
Today, all computers, even phones, delegate the I/O to dedicated hardware, so the term mainframe really just means a large computer that does a lot of data-processing that is usually located in a different location than the users.
I think that a lot of ‘explanations’ here never really address the difference between a mainframe and just like a regular beefy (set of) x86-based server(s) (filled with Xeons or Epycs).
From what I understand is that they are tuned for extremely high volume transaction processing although I can’t explain how this is achieved.
Also the redundancy / resilience is extreme with support for hot-swap CPUs! To prevent down time.
Somebody must be able to explain this better than me.
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