[PhasmaFelis]

What exactly is a "mainframe" in a modern sense? I thought it exclusively referred to old-fashioned big iron. Is it a cluster? Or are we actually talking about quarter-century-old monoliths running ancient, indispensable code?

[mastax]

https://en.wikipedia.org/wiki/IBM_mainframe

These are completely disconnected from commodity hardware. They are descendents of System/360, with a completely custom architecture and "mainframe processors" which only run specific types of code (Java, XML, DB2).

Or that's what I gather from wikipedia anyway.

[sitharus]

sort of. The run z/Architecture CPUs which implement a lot of backwards compatibility.

In the old days you had various modules you connected with dedicated CPUs for certain tasks, you'd pay more for them. These days they have a bunch of CPUs and the amount of money you pay IBM determines what those CPUs can do.

There's no physical difference between the Linux CPU, the DB2 CPU and the Java CPU, they're all the same as the main CPUs. IBM just charge you more for general purpose CPUs.

[PeterisP]

Ahh, I recall that we ordered an upgrade of the system hardware because we needed 4 more CPUs, and this was accomplished by sending a code that unlocked extra CPUs that had been sitting in our basement all along since the day they installed that system.

[rollthehard6]

At one point Sun had a similar model before RHEL + VMWare ate their lunch - https://docs.oracle.com/cd/E19095-01/sfe2900.srvr/819-1269-1...

[stillworks]

IBM do the same for P series as well. You get the privilege of purchasing an 8 core server but you only get the rights to use 4 cores. It's your responsibility to pay IBM when comes the time to be able to use all the 8 cores. Organized crime of sorts... like democracy

[rbanffy]

Actually, if the prices are pre-agreed, it's a sweet deal. If I have a big box serving my users, being able to enable additional on premises capacity in minutes is nice.

Last time I did it, Dell took several weeks to deliver the new machine.

[stillworks]

We didn't try but being speaking with the vendor it seemed that enabling extra cores could take about a week from raising a purchase order to the activation code coming through. Maybe larger customers who run hundreds of these may have a quicker turn around time dealing directly with IBM.

And it's not that IBM deliver an entire server like in your case. For most practical applications, it's merely the case of adding CPUs to the pool of CPUs available to the PowerVM hypervisor. If you need to provision additional memory or IO, that needs to be accounted in as well.

That hypervisor is weird on it's own. It's part firmware part software.

If you have big box serving your users who solely rely on CPU cycles then yes, it's a sweet deal. And consider yourself very lucky if you have users who will immediately see better performance if you throw more CPU cycles at them.

[StudyAnimal]

It refers basically only to the IBM z/Architecture machines. (I think no one else makes them any more. There were some IBM compatible (heh) Japanese ones recently). You can call a cluster of PCs a supercomputer, but you cant call it a mainframe.(But you can run a cluster, or sysplex, of mainframes. It sounds over the top but it is actually quite common.) They are particularly considered mainframes when they run z/OS and work in batch mode especially running CICS or IMS based applications. As soon as it runs linux, or web services, or more interactive things, the same zSeries machine is slightly less mainframy. (Using USS is less mainframy than using TSO or ISPF btw heh)

[winestock]

Aside from embedded systems, mainframes are the natural state of computers. That is, over time, computers tend to converge on either embedded controllers for appliances, or big racks in back rooms doing big calculations.

http://www.winestockwebdesign.com/Essays/Eternal_Mainframe.h...

Plug: I wrote the above.

[snaky]

"Mainframe" in a modern sense is the Cloud - especially 'private cloud'.