You probably mean "TIMI" which is the user-visible ISA of IBM's "midrange" systems (ie. AS/400 or System/i) which was from the start meant as virtual machine ISA that is then mostly AOT transpiled into whatever hardware ISA OS/400 or i5/OS runs on. z/Architecture (S/360, ESA/390, what have you...) is distinct from that and distinct from PowerPC. Modern POWER and z/Architecture CPUs and machines are somewhat similar when you look at the execution units and overall system design, but the ISA is completely different and even the performance profile of the mostly similar CPU is different (z/Architecture is "uber-CISC" with instructions like "calculate sha256 of this megabyte of memory").
I learned Z80 assembly in 1987, x86 assembly somewhere '91-92 can't exactly remember but it was in '94 when I met IBM Assembler (yes they called Assembler language which is also confusing) and I was like "what is this sorcery where assembly has an instruction to insert into a tree".
