ZZZZOOMING IN ON THE IBM Z13 MAINFRAME PROCESSOR

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Column door Frank van der Wal

The new IBM z13 mainframe had been announced only one day prior to my last blog entry. Working mainly on mainframes I could not ignore this wonderful new machine. Since it is very much positioned to handle all the CAMS topics, I’ve decided to write in that spirit.

However, I felt that I missed out the real technical interesting stuff and although I want to cover more than only mainframes in this column, this version is still about the z13.

I would like to take you on a virtual tour, from outside to the inner depths of the system.

If you stand in front of the z13 you will see a nice black refrigerator-sized cabinet. And since it is developed in the States we are talking about the double-door version of a fridge. (How on earth could our American friends store their XXXL size meals otherwise).
If you were to open the left-side door, you would see a flat panel and keyboard for the management console controlling the Support Elements, basically two Intel Based servers (for redundancy) which manage the mainframe. Not to worry, these run Linux, not Windows… The rest of the left side is for I/O, and although impressive, I’m not going to dwell on that this time.
The right-hand door reveals the impressive power supplies, water cooling units and, tada …, the processor drawers. Now we’re talking!

The z13 can house 141 processors. Say What??? Yes, no typo here, 141.
In one of my previous blogs (in Dutch) I’ve talked about the 3 main processors on this earth, Intel, ARM and of course Power. Those outnumber the mainframe processor with ease, but from a technical point of view, the z13 processor is some piece of work.

Let’s get our hands dirty.

A processor consists of transistors. The transistor was invented by Bells lab, more than 60 years ago. It’s main function is to switch (and to amplify). Like the good old tubes before the transistor, they are able to either conduct or stop an electrical current by means of a small voltage applied to the ‘gate’. Like an ordinary switch, there is a terminal with a voltage on it, and if you were to press the switch the current would flow out of the other terminal. Instead of applying a physical force on the switch, a – small– electric current will do the job for you. That goes for tubes, and also for transistors. With the ‘go’ or ‘no-go’ of the electric current, we have binary ‘1’ and ‘0’.

The first transistor was an ugly big thing, but it worked. Over the last 60 years it has been refined, scaled-down and enhanced. Jumping straight into the z13 processor, there are nearly 4.000.000.000 little switches in this one single piece of technology. The space occupied is only 678 mm2. (For comparison, a 2 Euro coin has an area of 520 mm2). That means that on every mm2 (like a point you could draw with a pen) there are 5900 transistors. Putting 4 billion transistors on a small piece of silicon is one thing, but it wouldn’t do any good if you didn’t connect them… You can do the math, 4 billion times 3 = 12 billion terminals that have to be connected. To do so, there is more than 25 km of interconnection on that chip. It would take you a stiff 5 hours of walking to cover that distance and this resides on that 678 mm2. The intriguing part is that, although these numbers are somewhat beyond what one might grasp, the connections and transistors are real things. Tiny, but real.

Those 25 km of interconnects are approximately 0,5 nanometer (nm) thick. An atom of which the the chip is made is 0,2 nm thick, so we are talking 2 or perhaps 3 atoms that do what they have to do. To put the the nanometer (nm) into perspective, take a human hair, cut it 100.000 times lengthwise and you are roughly in the 0,2 nm space. Roughly, for it might be that you are a bit inaccurate here. Still, the narrow channels can transport electrons 5 billion times every single second. Transistors themselves consist of a handful of atoms. And they work.

As Arthur C. Clarke already mentioned many, many years ago: ”Any sufficiently advanced technology is indistinguishable from magic”.

And it’s true. Although every scientist can tell you exactly how those 4 billion transistors and 25 km of interconnection works, it’s still a miracle.

Anyhow, zooming out of the nano scale chips, we see a single processor with all it’s magic inside. In a z13 you can bolt down 141 of those pieces of technology. One step of zooming out further we see the vast amount of memory and Intput/Output (I/O) cards that are able to feed those hungry beasts.

It’s why IBM claims that the new z Systems z13 can handle 2.5 billion transactions a day, that’s 30.000 every single tick…

Pretty cool. Rather good stuff, I would say.