The Worst-Selling Microsoft Software Product of All Time: OS/2 for the Mach 20

Raymond Chen, writing for Microsoft DevBlogs: In the mid-1980's, Microsoft produced an expansion card for the IBM PC and PC XT, known as the Mach 10. In addition to occupying an expansion slot, it also replaced your CPU: You unplugged your old and busted 4.77 MHz 8088 CPU and plugged into the now-empty socket a special adapter that led via a ribbon cable back to the Mach 10 card. On the Mach 10 card was the new hotness: A 9.54 MHz 8086 CPU. This gave you a 2x performance upgrade for a lot less money than an IBM PC AT. The Mach 10 also came with a mouse port, so you could add a mouse without having to burn an additional expansion slot. Sidebar: The product name was stylized as MACH [PDF] in some product literature. The Mach 10 was a flop.

Undaunted, Microsoft partnered with a company called Portable Computer Support Group to produce the Mach 20, released in 1987. You probably remember the Portable Computer Support Group for their disk cache software called Lightning. The Mach 20 took the same basic idea as the Mach 10, but to the next level: As before, you unplugged your old 4.77 MHz 8088 CPU and replaced it with an adapter that led via ribbon cable to the Mach 20 card, which you plugged into an expansion slot. This time, the Mach 20 had an 8 MHz 80286 CPU, so you were really cooking with gas now. And, like the Mach 10, it had a mouse port built in. According to a review in Info World, it retailed for $495. The Mach 20 itself had room for expansion: it had an empty socket for an 80287 floating point coprocessor. One daughterboard was the Mach 20 Memory Plus Expanded Memory Option, which gave you an astonishing 3.5 megabytes of RAM, and it was high-speed RAM since it wasn't bottlenecked by the ISA bus on the main motherboard. The other daughterboard was the Mach 20 Disk Plus, which lets you connect 5 1/4 or 3 1/2 floppy drives.

A key detail is that all these expansions connected directly to the main Mach 20 board, so that they didn't consume a precious expansion slot. The IBM PC came with five expansion slots, and they were in high demand. You needed one for the hard drive controller, one for the floppy drive controller, one for the video card, one for the printer parallel port, one for the mouse. Oh no, you ran out of slots, and you haven't even gotten to installing a network card or expansion RAM yet! You could try to do some consolidation by buying so-called multifunction cards, but still, the expansion card crunch was real. But why go to all this trouble to upgrade your IBM PC to something roughly equivalent to an IBM PC AT? Why not just buy an IBM PC AT in the first place? Who would be interested in this niche upgrade product?

Read more of this story at Slashdot.