[ASalazarMX]

Also, IBM mainframes are wonderfully isolated from physical hardware. They could change processors in the next model, and users would notice a small delay as binaries were recompiled on-the-fly the first time it was used.

They surely could extract more performance from the hardware by shedding layers, but prioritized stability and compatibility.

[rbanffy]

> Also, IBM mainframes are wonderfully isolated from physical hardware. They could change processors in the next model, and users would notice a small delay as binaries were recompiled on-the-fly the first time it was used.

This was with AS/400's move from their own CISC processors to POWER. While you could pull that off with mainframes, it'd be recompiling actual native binary code. IBM mainframe architecture is very well defined and documented (sadly, unlike AS/400).

This [0] describes it in depth.

0- https://www.ibm.com/docs/en/SSQ2R2_15.0.0/com.ibm.tpf.toolki...

[ASalazarMX]

I stand corrected. I experienced that change, and it was seamless, but AS/400 was a midrange, not a mainframe.

[rbanffy]

At this point in time it can have more cores and more memory than a Z, and likely higher performance in benchmarks, but the architecture is closer to a minicomputer than a mainframe.

It’s an odd lineup.