INSIDE IBM PC 5150
The first IBM PC
Thirty five years ago, in August 1981, IBM launched the most influential commercial computer system of all time, the IBM PC 5150. Over the past three and a half decades, architectural descendants of this single machine have taken over the desktop, workstation, server and even game console markets. And despite inroads from ARMbased smartphones, its digital descendants are still relied upon for just about all the heavy lifting in the computer industry.
On the anniversary of such a monumentally important computer, we thought it would be instructive to take a deeper look into the machine that started it all. How? By taking apart one of these bad boys on my trusty workbench, of course. And that’s exactly what you’ll see in the images ahead.
IBM’s CGA display
Before we take apart the IBM PC, we’d like to point out a few peripheral components that come together to form a complete IBM PC system. The most obvious component is the monitor. Many screens were available for the IBM PC in the years following its release, including an IBM brand monochrome unit and the IBM CGA monitor you see here (on which we’re playing the shareware classic ZZT). This monitor required the optional purchase of a CGA video card. In its standard 320x200 graphics mode, the CGA could display only four colours at a time from a palette of 16. In this case, ZZT uses text-mode graphics, so it can display any of the 16 colours at once.
The first IBM PC keyboard
The first IBM PC keyboard, seen here, borrowed heavily from the industrial-strength IBM System/23 Datamaster computer which preceded it. The keyboard is hefty (around 2.7kg), loud and clicky, and its layout was slightly unusual at the time of its launch. (It wouldn’t be until the Model M keyboard in 1984 that the standard 101-key layout we all know and use today would be finalised.)
Despite its awkward layout, this first PC keyboard won high praise from critics for its precision and durability. You could knock someone stone cold unconscious with it and it would still work. In the 1980s, we used to test computers that way.
Cracking the case
The only things separating us from the inside of an IBM PC were five precision flathead IBM screws, which came out easily. The heavy gauge sheet metal case slides off with no trouble, exposing the machine’s insides.
You can’t see it too clearly in this photo, but we always like to point out that the IBM PC first shipped with a cassette drive port (right next to the keyboard port), which allowed users without floppy drives to save their IBM BASIC programs to an audio cassette tape. In 1981, floppy drives were an expensive option, so IBM covered every possible market segment with custom build options – from bare-bones to decked-out.
Benj Edwards rewinds the clock by 35 years and revisits one of the PCs that started it all