That was my first thought too, but it does not make sense, because if IBM would sell ARM-based servers nobody would buy from them instead of using cheaper alternatives.
As revealed in another comment, at least for now their strategy is to provide some add-in cards for their mainframe systems, containing an ARM CPU which is used to execute VMs in which ARM-native programs are executed.
So this is like decades ago, when if you had an Apple computer with a 6502 CPU you could also buy a Z80 CPU card for it, so you could also run CP/M programs on your Apple computer, not only programs written for Apple and 6502.
Thus with this ARM accelerator, you will be able to run on IBM mainframes, in VMs, also Linux-on-ARM instances or Windows-on-ARM instances. Presumably they have customers who desire this.
I assume that the IBM marketing arguments for this are that this not only saves the cost of an additional ARM-based server, but it also provides the reliability guarantees of IBM mainframes for the ARM-based applications.
Taking into account that today buying an extra server with its own memory may cost a few times more than last summer, an add-in CPU card that shares memory with your existing mainframe might be extra enticing.
The architecture might be non-standard and not very widespread however for what it does and workloads that are suited to it. I dont think any ARM design comes close , maybe Fujitsu's A64FX.
Sun had the same problem after 2001 dotcom when standard PC servers became reliable enough to run web servers on.
It's easier to sell "our special sauce" when building using a custom ARM platform. Then you have no easy comparison with standard servers.
They will probably market the ARM inclusion similarly - as something that the package provides.
As far as POWER i think only Raptor[1] does direct marketingof the power(hehe) and capabilities
https://www.ibm.com/products/power
The i systems are just POWER machines with different firmware.
Why do you say "starting to"? arm64 has been competitive with ppc64le for a fairly long time at this point
The recent generations of IBM POWER CPUs have not been designed for good single-thread performance but only for excellent multi-threaded performance.
So I believe that an ARM CPU from a flagship smartphone should be much faster in single thread that any existing IBM POWER CPU.
On the other hand, I do not know if there exists any ARM-based server CPU that can match the multi-threaded performance of the latest IBM POWER CPUs.
At least for some workloads the performance of the ARM-based CPUs must be much lower, as the IBM CPUs have huge cache memories and very fast memory and I/O interfaces.
The ARM-based server CPUs should win in performance per watt (due to using recent TSMC processes vs. older Samsung processes) and in performance per dollar, but not in absolute performance.
And the single thread side isn't that good either, but SMT8 is a quite nice software licensing trick
But I could be wrong… I’m going from a historical perspective. I haven’t checked PPC benchmarks in quite a while.
Motorola made CPUs with this ISA. Apple used CPUs with this ISA, some made by IBM and some made by Motorola.
While Motorola and Apple used the name "PowerPC", IBM continued to use the original name "POWER" for its server and workstation CPUs. Later IBM sold its division that made CPUs for embedded applications and for PCs, retaining only the server/workstation CPUs.
However, nowadays, even if the official IBM name is "POWER", calling it "PowerPC" is not a serious mistake, because all the "PowerPC" ISA changes have been incorporated many years ago into the POWER ISA.
So the current POWER ISA is an evolution of the PowerPC ISA, which was an evolution of the original 1990 POWER ISA.
It is better to call it POWER, as saying "PowerPC" may imply a reference to an older version of the ISA, instead of referring to the current version, but the 2 names are the same thing. PowerPC was an attempt of rebranding, but then they returned to the original name.
Legacy apps on s390x do not move because IBM put out a press release and IBM does not get fatter cloud margins by joining the same ARM pile as other vendors. Mainframe migration is not a weekend project. "Easier" usually means somebody signs a six digit check first.