In this post and subsequent ones, I will discuss the main hardware concepts of mainframe environments. I will not go into the tiniest detail, but I must be a bit technical. To make things easier to understand, I will compare the mainframe technology with mainstream x86 and Unix technology. You will see there is often a difference in terminology.

The mainframe has a long history. Some hardware terminology is different from what we know. To get some understanding of this hardware we need to talk a little bit about mainframe jargon.

This post appears as part of a number of articles in the category “Don’t Be Afraid Of The Mainframe.

A box full of CPU and memory

A mainframe is a large refrigerator-size box with computing capacity. The box houses the computing units, the CPUs. These are not x86 CPU’s like in your PC. But a mainframe uses CPU’s build according to the processor architecture called IBM z/Architecture.

In your PC, the CPU, the memory and other chips are soldered on a motherboard. Like in your PC, you find a sort of motherboard in the big mainframe box. The mainframe motherboard is called a drawer.  The drawer is a bit bigger than your PC motherboard because it carries more components.

On the drawer the CPU and memory chips for the mainframe are soldered, and some more components.  A drawer can have a number of CPU chips. In the z14 model the number of CPU chips in a drawer can be 6.

Each CPU chip on the drawer has a number of processor cores, the actual CPUs. The number of processor cores varies per mainframe model. In the z14 mainframe model there are 10 cores on a chip.

Finally you can have multiple drawers in a mainframe box. In the z14 there can be 4 drawers.

Now let’s count. You can have a maximum of 4 drawers, each with a maximum of 6 CPU chips, each chip with 10 cores. Thus, you can have 240 processor cores in a mainframe box – the z14 model to be precise. The mainframe uses a number of these 240 cores for internal processing. For you as a mainframe user up to 170 processor cores in a single mainframe box. 

You also need memory. Every drawer can have a maximum of 8 TB of memory in the z14. So in total you can have 32TB of memory in your z14 mainframe.

Enfin, a lot of computing power.

What else is in the box

Besides the main computing elements, CPU and memory, the mainframe server contains almost everything else needed. Power supplies, network cards, cooling devices, I/O cards, and more .

To make sure the mainframe can continue running when one of these components fails, you find at least two items of these components in a mainframe.

In the picture of Figure 3 you can see the following components:

• Processor drawers – as we saw, the motherboard of the mainframe. There can be multiple processor drawers in a machine, depending on the number of CPUs you have ordered.
• PCIe Input Output drawers in which cards are configured for networking equipment, IO interfaces (disk, tape, server-to-server connections) and additional facilities such as encryption and compression. PCIe is a standard for interfaces in a computer.
• Cooling components to regulate the temperature. A mainframe box can be water-cooled or air-cooled, by the way.
• Power supplies to provide power for the components in the machine.

All in all, it looks very much like a normal computer, but a little bigger.

In the picture you also see two laptops. As we will see later, the big box needs to be configured. The two laptops are so-called support elements. With these support elements you can configure the hardware, and also monitor the state of the hardware.

More technical information on mainframe hardware can be found here:

https://www.ibm.com/support/knowledgecenter/zosbasics/com.ibm.zos.zmainframe/zconc_mfhardware.htm