I've been playing with OS/2 again -- more on that soon -- but it was doomed from a young age

OS/2 2.0 came out in April 1992.

Windows 3.0 came out in May 1990, 2 whole years earlier. It already had established an ecosystem before 32-bit OS/2 appeared.

Secondly, OS/2 2 really wanted a 386DX and 4MB of RAM, and a quality PC with quality name-brand parts. I owned it. I ran it on clones. I had to buy a driver for my mouse. From another CONTINENT.

Windows 3.0 ran on any old random junk PC, even on a PC XT class box with EGA. At first only high-end users of high-end executive-class workstations got the fun of 386 Enhanced Mode, but that was all OS/2 2.0 could run on at all.

OS/2 died when OS/2 1.x was a high-end OS with low-end features, and a cheapo low-end 386SX PC with 1 or 2MB of RAM, with MS-DOS and DESQview (not DESQview/X, just plain old text-mode DESQview) could outperform it.

(Remember the 386SX came out in 1988 and was common by the time Windows 3.0 shipped.)               

But as soon as OS/2 1.x was a flop, MS turned its attention back to Windows, and before even the first betas of Windows 3.0, there were rumours in the tech press that MS was going to abandon the project. This was widely discussed in the media at the time.

In my then-job, around 1989, my boss sent me on a training course for 3Com's new NOS, 3+Open, which was based on OS/2 1.0.

I did not realise it was a clever evaluation strategy. He knew I might have enthused about it if given a copy to play with. Instead, being trained on it, I was told some of the holes and weaknesses.

I came back, told them it was good but only delivered with OS/2 clients and had no compelling features for DOS clients, and they were very pleased -- and the company went on to start selling Novell Netware instead.

Looking back that was a good choice. In the late 1980s Netware 2 and 3 were superb server OSes for DOS, and OS/2 with LAN Manager wasn't.

But yes, I think from soon after OS/2 launched, it was apparent and widely reported to IBM that MS was not happy, and as soon as MS started talking about launching a new updated version of Windows -- circa 1989 -- it was very clear to IBM that MS was preparing a lifeboat and would soon abandon ship. By the time Windows 3.0 came out MS had left the project. Its consolation prize was to keep Portable OS/2, also called OS/2 3.0, later OS/2 NT.

This wasn't secret, and everyone in the industry knew about it. The embarrassment to IBM was considerable and I think that's why IBM threw so many people and so much money at OS/2 2.x. It was clear early on that although it was a good product, it wasn't good enough.

NT 3.1 launched in July 1993, almost exactly 1 year before OS/2 2.1, and NT made it pretty clear that OS/2 2.x was toast.

I deployed NT 3.1 in production and supported it. Yes, it was big and it needed a serious PC. OS/2 2.0 was pretty happy on a 486 in 4MB of RAM and ran well in 8MB. NT 3.1 needed 16MB to be useful and really wanted a Pentium.

But NT was easier to install. For instance, you could copy the files from CD to hard disk and then run the installer from MS-DOS. OS/2 had to boot to install, and it had to boot with CD drivers to install from CD. Not trivial to achieve: ATAPI CD-ROM drives hadn't been invented yet. It was expensive SCSI drives and a driver for your SCSI card, or proprietary interfaces and proprietary drivers, and many of those were DOS-only.

NT didn't have OS/2's huge, complicated CONFIG.SYS file. NT had networking and sound and so on integrated as standard, while they were paid-for optional extras on OS/2.

And NT ran Windows 3 apps better than OS/2, because each Windows 3 app had its own resource heaps under NT. Since the 64kB heap was the critical limitation on Win3 apps, NT ran them better than actual Windows 3.

If you could afford the £5000 PC to run NT, it was a better OS. OK, its UI was the clunky (but fast) Windows 3 Program Manager, but it worked. OS/2's fancy Workplace Shell was more powerful but harder to use. E.g. why on earth did some IBMer think needing to use the right mouse button to drag an icon was a good idea?

I owned OS/2, I used it, and I liked it. I am still faintly nostalgic for it.

But aside from the fancy front-end, NT was better.

NT 3.5 was smaller, faster and better still. NT 3.51 was even smaller, faster and stabler than that, and was in some ways the highpoint of NT performance. It ran well in 8MB of RAM and very well in 16MB. On 32MB of RAM, if you were that rich, we NT users could poke fun at people with £20K-£30K UNIX workstations, because a high-end PC was as fast, as stable, and had a lot more apps and a much easier UI.

Sad to say, but the writing was on the wall for OS/2 by 1989 or so, before 2.0 even launched. By 1990 Windows 3.0 was a hit. By 1992 Windows 3.1 was a bigger hit and by 1993 it was pretty clear that it was all over bar the shouting.

There was a killer combination that had a chance, but not a good one: Novell Netware for OS/2. Netware ran on OS/2 and that made it a useful non-dedicated server. IBM could have bought Novell, combined the products, and had a strong offering. Novell management back then were slavering to outcompete Microsoft; that's why Caldera happened, and why Novell ended up buying SUSE.

(For whom I worked until last year.)

OS/2 plus Netware as a server platform had real potential, and IBM could have focussed on server apps. IBM had CC:Mail and Lotus Notes email, it had the DB2 database, soon it would have Websphere. It had the products to bundle to make OS/2 a good deal as a server, but it wanted to push the client.               

How to tell a mainframe from a minicomputer from a micro

Mainframes: the first style of computer. Primarily designed as a batch-oriented system, meaning that they are not directly interactive. Jobs are queued up, run without interaction, results stored, and then the next job processed. Later models added interactivity as a secondary feature, usually like most mainframe I/O handled by intelligent peripherals which in effect are networked to the main processors. So, the terminal, on its own, shows a form and then handles all user input as the user completes the form, without communicating with the host at all. Then, when the user signals that the form is complete, the entire contents, maybe many pages, are sent as a single message to the host.

Separate processors in storage, in terminals, in networking controllers, in printers, in everything. Typically the machine cannot actually drive any output or input directly (e.g. mouse movements, or keystrokes, or anything): peripherals do that, collect and encode the results, and send them over a network. So as someone else commented, a mainframe isn't really a computer, it's a whole cluster of closely-coupled computers, many with dedicated functionality. Quite possibly all implemented with different architectures, instruction sets, programming languages, bit widths, everything.

Here's an article I wrote about a decade back about how IBM added the new facility of "time sharing" -- i.e. multiple users on terminals, all interacting with the host at the same time -- by developing the first hypervisor and running 1 OS per user in VMs, because the IBM OSes of the time simply could not handle concepts like "terminal sessions".

Minicomputer: the 2nd main style of computer. Smaller, cheaper, so affordable for a company department to own one, while mainframes were and are mostly leased to whole corporations. Typically 1 CPU in early ones, implemented as a whole card cage full of multiple boards: maybe a few boards with registers, one with an adder, etc. The "CPU" is a cabinet with thousands of chips in it.

Hallmarks: large size; inherently multitasking, so that multiple users can share the machine, accessing it via dumb terminals on serial lines. User presses a key, the keystroke is sent over the wire, the host displays it. Little to no networking. One processor, maybe several disk or tape drives, also dumb and controlled by the CPU. No display on the host. No keyboard or other user input on the host. All interaction is via terminals. But because they were multiuser, even the early primitive ones had fairly smart OSes which could handle multiple user accounts and so on.

Gradually acquired networking and so on, but later.

In some classic designs, like some DEC PDPs, adding new hardware actually adds new instructions to the processor's instruction set.

Wildly variable and diverse architectures. Word lengths of 8 bit, 9 bit, 12 bit, 18 bit, 24 bit, 32 bit, 36 bit and others. Manufacturers often had multiple incompatible ranges and maybe several different OSes per model range, depending on the task wanted, so offering dozens of totally different and incompatible OSes across half a dozen models.

Microcomputer: the simplest category. The entire processor is implemented on a single silicon chip, a microprocessor. Early machines very small and simple, driven by 1 terminal with 1 user. No multitasking, no file or other resource sharing, no networking, no communications except typically 1 terminal and maybe a printer. Instead of 1 computer per department, 1 computer per person. Facilities added by standardised expansion cards.

This is the era of standardisation and commoditisation. Due largely to microcomputers, things like the size of bytes, their encoding and so on were fixed. 8 bits to a byte, ASCII coding, etc.

Gradually grew larger: 16-bit, then 32-bit, etc. In the early '80s gained onboard ROM typically with a BASIC interpreter, on-board graphics and later sound. Mid-'80s, went to 16-bit with multicolour graphics (256+ colours), stereo sound. Lots of incompatible designs, but usually 1 OS per company, used for everything. All single-user boxes.

These outperformed most minis and minis died out. Some minis gained a hi-res graphical display and turned into single-user deskside "workstations", keeping their multitasking OS, usually a UNIX by this point. Prices remained at an order of magnitude more than PCs, and processors were proprietary, closely-guarded secrets, and sometimes still implemented across multiple discrete chips. Gradually these got integrated into single chip devices but they usually weren't very performance competitive and got displaced by RISC processors, built to run compiled C quickly.

In the '90s, generalising wildly, networking became common, and 32-bit designs became affordable. Most of the 16-bit machines died out and the industry standardised on MS Windows and classic MacOS. As internet connections became common in the late '90s, multitasking and a GUI were expected along with multimedia support.

Apple bought NeXT, abandoned its proprietary OS and switched to a UNIX.

Microsoft headhunted DEC's team from the cancelled MICA project, merged it with the Portable OS/2 project, and got them to finish OS/2 NT, later Windows NT, on the N-Ten CPU, the Intel i860, a RISC chip, then on MIPS, and later on x86-32 and other CPUs. This was the first credible commercial microcomputer OS that could be both a client and a server, and ultimately killed off all the proprietary dedicated-server OSes, of which the biggest was Novell Netware.

That is a vastly overlong answer but it's late and I'm just braindumping.

Mainframe: big tightly-clustered bunch of smart devices, flying in close formation. Primary role, batch driven computing, non-interactive; interactivity bolted on later.

Mini: departmental shared computer with dumb terminals and dumb peripherals, interactive and multitasking from the start. Most text-only, with interactive command-line interfaces -- "shells" -- and multiprogramming or multitasking OSes. Few had batch capabilities; no graphics, no direct I/O, maybe rare graphical terminals for niche uses. Origins of the systems that inspired CP/M, MS-DOS, VMS, UNIX, and NT.

Micro: single-chip CPU, single-user machines, often with graphics and sound early on. Later gained GUIs, then later than that networking, and evolved to be servers as well.

If the machine can control and be controlled by a screen and keyboard plugged into the CPU, it's a micro. If its CPU family has always been a single chip from the start, it's a micro. If it boots into some kind of firmware OS loader, it's probably a micro. The lines between micros and UNIX workstations are a bit blurred.