A Tour Inside the IBM Z17

I encountered assembly programs written and compiled in '88 and still running.

There are several drawbacks to maintaining this kind of compatibility but, nevertheless, it's impressive.

Book recommendation: in-depth on the people, processes, and technology. Incredible detail on all aspects.

https://direct.mit.edu/books/monograph/4262/IBM-s-360-and-Ea...

Besides all answers given already, one of the reasons Unisys keeps selling Burroughs, aka ClearPath MCP, is its security model.

ESPOL/NEWP is one of the very first systems programming languages, being safe by default, with unsafe code blocks.

The whole OS was designed with security first in mind, think Rust in 1961, thus their customers are companies that take this very seriously, not only running COBOL.

The motto is unsurpassed security.

https://www.unisys.com/product-info-sheet/ecs/clearpath-mast...

> Who uses mainframes nowadays and what for?

Large institutions (corporations, governments) that have existed more than a couple decades, and have large-scale mission-critical batch processes that run on them, where the core function is relatively consistent over time. Very few, if any, new processes are automated on mainframes most of these places, and even new requirements for the processes that depend on the mainframe may be built in other systems that process data before or after the mainframe workflows, but the cost and risk of replacing the well-known, finely-tuned-by-years of ironing out misbehavior, battle-tested systems often isn't warranted without some large scale requirements change that invalidates the basic premises of the system. So, they stay around.

All these legacy answers don't really make sense for this Z17... it's a new mainframe supporting up to 64T of memory and specialized cores for matrix math/AI applications. I have a hard time believing that legacy workloads are calling for this kind of hardware.

It also has a ton of high availability features and modularity that _does_ fit with legacy workloads and mainframe expectations, so I'm a little unclear who wants to pay for both sets of features in the same package.

If I were a bank, I'd order one of those and put all the financial modelling and prediction load on it. Like real time analysis to approve/deny loans, do projections for deciding what to do in slower moving financial products, predicting some future looking scenarios on wider markets, etc. etc. simultaneously.

That thing is dreadnought matmul machine with some serious uptime, and can crunch numbers without slowing down or losing availability.

or, possibly, you can implement a massively parallel version of WOPR/Joshua on it and let it rip scenarios for you. Just don't connect to live systems (not entirely joking, though).

P.S.: I'd name that version of the Joshua as JS2/WARP.

The funny thing is that if they spun out half of the mainframe thing into something they could compete with people might actually buy them.

Most firms have so-so software, in need of ultra reliable hardware, not everyone is google

> I don't mean this in a condescending way at all, but really out of sheer curiosity: Who uses mainframes nowadays and what for?

There's probably some minor strategic relevance here. E.g. for the government which has some workloads (research labs, etc.) that suit these systems, it's probably a decent idea not to try and migrate over to differently-shaped compute just to keep this CPU IP and its dev teams alive at IBM, to make sure that the US stays capable of whipping up high-performance CPU core designs even if Intel/AMD/Apple falter.

I understand that a company I work with uses a few, and is migrating away from them.

It seems clear to me that prior to robust systems for orchestrating across multiple servers that you would install a mainframe to handle massive transactional workloads.

What I can never seem to wrap my head around is if there are still applications out there in typical business settings where a massive machine like this is still a technical requirement of applications/processes or if it's just because the costs of switching are monumental.

I'd love to understand as well!

Cloud is basically an infinitely scalable mainframe. You have dedicated compute optimised for specific workloads, and you string these together in a configuration that makes sense for your requirements.

If you understand the benefits of cloud over generic x86 compute, then you understand mainframes.

Cloud is mainframes gone full circle.

I think what you are referring to is the "sub capacity" pricing model wherein a rolling average of resource consumption is used for billing. They've transitioned to newer models circa cloud technology, but it's mostly the same idea with more moving parts.

The advantage of this model from a business operations standpoint is that you don't have to think about a single piece of hardware related to the mainframe. IBM will come out automagically and fix issues for you when the mainframe phones home about a problem. A majority of the system architecture is designed on purpose to enable seamless servicing of the machine without impacting operations.

https://www.ibm.com/z/pricing

I haven't worked with mainframes since the z10, but back then you could get into an entry model for about $100k.

Though the sky is the limit. The typical machine I would order had a list price of about 1 million. Of course no one pays list. Discounts can be pretty substantial depending on how much business you do with IBM or how bad they want to get your business.

The big problem is that everything in IBM-z world is negotiated, and often covered by NDAs. The pricing is complicated by which operating systems and what sort of workloads you'll be running, and what service level guarantees you need. The only published pricing in the entire life of the IBM 360/370/390/z-series line was the Linux One when it was first released... Hardware plus OS, excluding storage, was $70k on the low end.

Previous generation machines that came off-lease used to be listed on IBM's web site. You could have a fully-maxed-out previous-generation machine for under $250k. Fifteen years ago I was able to get ballpark pricing for a fully-maxed-out new machine, and it was "over a million, but less than two million, and closer to the low end". That being said, the machines are often leased.

If you go with z/vm or z/vse, the OS and softare is typically sold under terms that are pretty much like normal software, except it varies depending on the capacity level of the machine, which may be less than the physical number of CPUs in the machine, since that is a thing in IBM-land.

If you go for z/os, welcome to the world of metered billing. You're looking at tens of thousands of dollars in MRC just to get started, and if you're running the exact wrong mix of everything, you'll be spending millions just on software each month. There's a whole industry that revolves around managing these expenses. Still less complicated than The Cloud.

You can get a software emulator for free and run it on a PC! It's quite robust and used by IBM's own developers. https://en.wikipedia.org/wiki/Hercules_(emulator)

You don't buy a mainframe, it's consumption based pricing. They aren't just going to list a price, because they need to size the hardware to what they think the workload will be.

Could they just list prices? Sure. Will they ever do it? No.

A Rockhopper 4 Express starts at $135,000. While technically a mainframe, it won't run z/OS.

It depends on how full those drawers are. $250k to $1m would be the typical price range.

It's easier and harder at the same time to buy older hardware. That's half the challenge though because the software is strictly licensed and you pay per MIPS.

Here's a kid who bought a mainframe and then brought it up:

https://www.youtube.com/watch?v=45X4VP8CGtk

If you have to ask, you can't afford it!

https://www.redbooks.ibm.com/abstracts/sg248579.html:

“The IBM z17 supports a PCIe I/O infrastructure. PCIe features are installed in PCIe+ I/O drawers. Up to 12 I/O drawers per IBM z17 can be ordered, which allows for up to 192 PCIe I/O and special purpose features.

For a four CPC drawer system, up to 48 PCIe+ fan-out slots can be populated with fan-out cards for data communications between the CPC drawers and the I/O infrastructure, and for coupling. The multiple channel subsystem (CSS) architecture allows up to six CSSs, each with 256 channels.

The IBM z17 implements PCIe Generation 5 (PCIe+ Gen5), which is used to connect the PCIe Generation 4 (PCIe+ Gen4) dual port fan-out features in the CPC drawers. The I/O infrastructure is designed to reduce processor usage and I/O latency, and provide increased throughput and availability.”

There's also the problem in that they need to take into account floor loading. They're not going to tell a customer upgrading from an older machine to a new one that, "oh, by the way, the rack weighs twice what it used to, so you'll need to upgrade your floor while you're at it." Especially important for raised floors.

Probably channels. In an IBM mainframe, each I/O device is connected on its own channel, which is actually a separate computer that handles the transfer to/from the main CPU. This has been the case going back to the System/360, which is why mainframes are legendary for their transaction throughput and reliability. There's probably a lot of redundancy in the I/O hardware, as they have to be rock solid and hot swappable while the system is running.

Could be storage, networking, crypto HSM, or cluster interconnect. See page 28 on https://www.redbooks.ibm.com/redbooks/pdfs/sg248580.pdf

Reading about mainframes feels very much like reading science fiction. Truly awesome technology that exists on a completely different plane of computing than anything else.

Yeah a few years ago there was a Talos (I think) desktop motherboard that had a POWER 8 cpu in it. It was expensive due to low production runs but I wish it had taken off. I think IBM is up to power 9 now, but I doubt if there are any personal motherboards for it.

To be fair, AWS copied the concept of mainframe with x86 and "commodity" hardware, including the consumption based billing.

Have you seen the size of those drawers? A single rack can only fit five of them, and you still would need to add processing, power/UPS, and cooling.