5150: Significance of the IBM PC 5150


The B in IBM means Business. That means numbers, calculations, sorting, databases. And IBM has been in business since 1911, producing all sorts of calculation and processing machines (see IBM 1401 and the System/360) for large companies all over the world (in domains such as airlines, stock markets, insurance companies, world wide magazine companies, government records).

Business means calculating area to determine material costs, optimizing shipping loads and delivery routes, all part of the job and software helped get it done. From building highways, power plants, water treatment plants, coordinating planes, trucks, boats to provide supplies to factories, sending rockets to the moon, and managing all the flows of money that ultimately cause all this happen. Large computers had helped large companies with all this since the 1950s.

A viable personal computer within ones home was established in 1977, first by Commodore (PET), then Apple and Tandy. Commodore did initially have aspiration of making professional business oriented equipment (the B in CBM also meant Business). But in 1980, Commodore went astray with the VIC-20, following along with the ColecoVision, IntelliVision, Atari 2600, Color Computer. Even the Apple ][ was initially a game-oriented system, with paddles and sacrificing floating-point support in order to have improved integer-performance.

The home computing market was initially in full right-brain mode. However, the Apple 2 was the first system (in 1979) to have VisiCalc, the first spreadsheet application. And IBM, being a very left-brained organization, took notice of all this: microprocessors were reliable and capable enough to do useful applications. IBM realized they were about to be left behind. So while the home computer market was distracted with essentially “toy” game machines, IBM put in motion plans to make their own entry into this new personal computer market. And to emphasize this entry, they called their system “PC”: Personal Computer. A ingenious name since from that point forward, anyone saying “PC” would implicitly be referring to IBM equipment.

The idea of “personal computers” was still quite new to the world in the 1970s. For reference, just see some of the articles in the 1978 People’s Computer magazine (see here), But the population was growing, standards of living was rising. A personal computer would help even small businesses manage finances, inventory, and schedules. Pool cleaners, auto-garages, local news papers, church groups and local clubs — anyone who needed to maintain contact list and invoice records, all benefited by having their own computer.

To put all this competition to rest, in 1981 IBM launched their entry into the “personal computer” market: the IBM PC 5150. While the project was done swiftly and largely in secret (with a number of NDA signed with various partners), IBM did have a vast amount of in-house experience in engineering a computer system (from the System/360, IBM 5100 series, and Datamaster). But the 5150 was a distinct focused departure from the Big-Blue norm.

While not the best equipment at the start, that wasn’t the point: the point was a sustainable and expandable system. Use of off the shelf components and published specifications to facilitate a more modular expansion. And companies like Compaq quickly took advantage of this, to build “IBM PC clones” (so all the software was compatible with the system, just these clones weren’t built or sold by IBM).

This wasn’t just a cute limited-capability game machine. Adults used these systems to conduct business: to store records (contacts), manage inventory, run reports, conduct accounting, and conduct word processing. The 80 column MDA was crisp and there was no excess expense for color or sound – the expense was put into being a productive system. The DOS was also straightforward and no nonsense: drive letters and 8.3 filenames. But kids could also use these machines, they were capable enough for a few modest games. There were other options that lingered on the market, but the IBM brand was trusted, and had made a grand entrance into the Personal Computing market at the perfect time and price point. The Commodore PETs and TRS-80 systems were showing their age (32K-64K limited), and the IBM PC system was set to be an expandable option for years to come.

The entire computing industry has vastly evolved since those humble beginnings of 1978-1982. The earlier computers of the 1960s and early 1970s are generally just too physically massive to be practically stored, maintained, and used (in addition to being largely undocumented, or any documentation they had isn’t readily available in a digital format that can be searched upon). But the fundamental design and operation of the IBM PC was well documented, including full source of its BIOS. This has made emulating the system on modern hardware readily available.

But there are many early IBM PCs still available, still in good working condition. I feel it is important to sustain the know-how of using these systems, which is thus the focus of these notes. More modern systems certainly “run circles” around these ancestors in terms of capability. But these early systems represent the beginning of the Information Age and give witness to how that began, with very humble capabilities that focused on content while still having “raw access” to the bare-metal hardware itself.

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