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This feels like a baby step towards Arm being able to emulate z/Arch workloads, maybe with a bit of secret sauce for certain specific operations, which doesn't

This feels like a baby step towards Arm being able to emulate z/Arch workloads, maybe with a bit of secret sauce for certain specific operations, which doesn't seem very much like IBM.

nxobject 21d ago
I thought about that, too. I think they’re doing this for the same reason IBM has supported Linux LPARs: since a lot of customers who lease System/z currently probably get overprovisioned hardware that they’ll never fully use, why not try a last-ditch attempt to sell the excess capacity as ARM LPARs? Now you’re thinking like a Big Blue sales rep.
- rbanffy 21d ago
  IIRC, they had different licensing prices for cores that would run z/OS workloads and cores that would run Linux on s390x (and other tier for Java, I think). This looks like they’ll have one for Linux on ARM as well.
stinkbeetle 21d ago
ARM can emulate z workloads. https://hercules-390.github.io/html/index.html https://hercules-390.github.io/html/index.html (or QEMU, for partition level emulation).
- jasomill 21d ago
  Sure. And you can run ARM workloads under QEMU on s390x Linux.
  - stinkbeetle 21d ago
    Sure. And you can run ARM workloads in hardware ARM mode.
- CountHackulus 21d ago
  There's also the poorly advertised IBM-native S390 emulator. I worked on it over a decade ago, you could run S390 on PPC and X86 offically, and ARM and a few others were unofficial.
bitwize 21d ago
Not even the weirdest thing IBM did to get compatibility between their mainframes and other CPU architectures. To build the XT/370 and AT/370 expansion cards, they custom-ordered modified 68000s that decoded System/370 instructions instead of the 68k instruction set, with most of the instructions handled by the new microcode and the few stragglers software-emulated: https://en.wikipedia.org/w/index.php?title=PC-based_IBM_mainframe-compatible_systems#Personal_Computer_XT/370 https://en.wikipedia.org/w/index.php?title=PC-based_IBM_main...
- sillywalk 20d ago
  A couple more articles on them. https://thechipletter.substack.com/p/motorola-intel-ibm-make-a-mainframe https://thechipletter.substack.com/p/motorola-intel-ibm-make... https://www.cpushack.com/2013/03/22/cpu-of-the-day-ibm-micro-370/ https://www.cpushack.com/2013/03/22/cpu-of-the-day-ibm-micro...

This feels like a baby step towards Arm being able to emulate z/Arch workloads, maybe with a bit of secret sauce for certain specific operations, which doesn't seem very much like IBM.

nxobject 21d ago

I thought about that, too. I think they’re doing this for the same reason IBM has supported Linux LPARs: since a lot of customers who lease System/z currently probably get overprovisioned hardware that they’ll never fully use, why not try a last-ditch attempt to sell the excess capacity as ARM LPARs? Now you’re thinking like a Big Blue sales rep.

rbanffy 21d ago
IIRC, they had different licensing prices for cores that would run z/OS workloads and cores that would run Linux on s390x (and other tier for Java, I think). This looks like they’ll have one for Linux on ARM as well.

stinkbeetle 21d ago

ARM can emulate z workloads. https://hercules-390.github.io/html/index.html https://hercules-390.github.io/html/index.html (or QEMU, for partition level emulation).

jasomill 21d ago
Sure. And you can run ARM workloads under QEMU on s390x Linux.
- stinkbeetle 21d ago
  Sure. And you can run ARM workloads in hardware ARM mode.
CountHackulus 21d ago
There's also the poorly advertised IBM-native S390 emulator. I worked on it over a decade ago, you could run S390 on PPC and X86 offically, and ARM and a few others were unofficial.

bitwize 21d ago

Not even the weirdest thing IBM did to get compatibility between their mainframes and other CPU architectures. To build the XT/370 and AT/370 expansion cards, they custom-ordered modified 68000s that decoded System/370 instructions instead of the 68k instruction set, with most of the instructions handled by the new microcode and the few stragglers software-emulated: https://en.wikipedia.org/w/index.php?title=PC-based_IBM_mainframe-compatible_systems#Personal_Computer_XT/370 https://en.wikipedia.org/w/index.php?title=PC-based_IBM_main...

sillywalk 20d ago
A couple more articles on them. https://thechipletter.substack.com/p/motorola-intel-ibm-make-a-mainframe https://thechipletter.substack.com/p/motorola-intel-ibm-make... https://www.cpushack.com/2013/03/22/cpu-of-the-day-ibm-micro-370/ https://www.cpushack.com/2013/03/22/cpu-of-the-day-ibm-micro...