I have a special interest in IBM equipment since I was an application programmer on early IBM computers (1963-1965) and I worked at IBM for 21 years (1967-1988) having a very rewarding career. In the early 1960's I programmed applications in Fortran and assembly language for an IBM 7090 (along with some programming for an IBM 1401). Then, in college I did extensive assembly programming on an IBM 1620. After getting a Master's degree, I started with IBM in 1967 (in San Jose) as a programmer on the IBM 1130 and the IBM 1800 operating systems (these were a low-end scientific computer and a specialized process-control computer). I also worked on the initial definition of the 1800 follow-on: the IBM System/7.
Moving to Boca Raton, I became a manager of the BASIC operating system for the IBM System/3 Model 6. This little-known product was actually IBM's first "personal computer", albeit a little large: it was a desk with a keyboard, CRT monitor, removable disk and an attached printer. Its operating system was essentially a BASIC language interpreter.
Excitingly, the museum now has a (almost working) and complete System/3 Model 6. Check it out.
I then became the architecture for a proposed low-end System/360 computer, which morphed (along with my moving to Rochester, MN) into a business-oriented single-user computer: the IBM System/32. I managed the development of the system software for the System/32.
After the System/32, I started the initial architecture design for the IBM System/38 family. The "second-system effect" was clearly at work here; we decided to advance the state-of-the-art in many areas (and we did, although it took longer than we planned). In particular, innovations in the System/38 were:
The System/38 project ended up taking seven years; I ended up managing all the system software for the System/38: microcode, operating system, compilers, and miscellaneous utilities.
Next, moving to Austin, I started several advanced technology projects, one of which morphed into the IBM RT product (sometimes called the RT/PC). I ended up managing both the hardware and operating systems development for the RT. The RT was the first IBM product to use a RISC processor (the ROMP processor and a UNIX based operating system (IBM AIX). I also managed a project to define an IBM-wide AIX strategy.
At this point I was made an IBM Fellow and henceforth worked on my Fellow projects, the last of which was a processor that would merge the Intel x86 instruction set architecture with the IBM Power architecture. While this "L86" project ("last x86") never became a product, there are tendrils of its philosophy still embedded in my current company's x86 processors. There is even a few external references to the L86 in books, here's one.