Many of you will remember hours of playing in front of a Spectrum, an Amstrad CPC, a Commodore 64, an MSX, and so on. All of them were the computers that many of us had in the 80s, for some it is a fuzzy memory, others keep great memories when using them. That is why we have decided to make a tribute article to these computers. What points did 8-bit microcomputers have in common?
It must be taken into account that the IBM PC was a computer that was not designed to be used for homes, but in companies that were IBM’s main source of income. So most of the users made use of a microcomputer. Which used to have a common form factor, based on unifying all the circuitry and expansion ports on the keyboard. Also among them they used to use a series of common elements in their architecture, but each of them had its own software.
Nowadays everyone has a PC at home and it is rare who has not acquired it or at least is not in contact with one in their day to day, but it has not always been like that. In the 80s, it was normal for homes around the world to have what we call microcomputers, which consisted of a very rudimentary computer that was more like a video game console than a PC.
In those days a PC was extremely expensive and unattainable for most users and that is why microcomputers enjoyed great popularity in their day. Its most common use, however, was as a video game system and they were never used as computers beyond being a playful environment, although there were people who used them for certain office automation tasks, they were not their common use.
There was neither Intel nor AMD in the CPU
We can divide the 8-bit microcomputers into two different categories according to the CPU they used, on the one hand those that made use of the MOS 6502 and on the other those that made use of the Zilog Z80 . The latter was an improved version of the Intel 8080 or what could be called a clone.
Both were 8-bit processors with 16-bit addressing , so microcomputers could not have more than 64 KB of RAM . Which of them was better? Although both were 8-bit processors in terms of philosophy, they were completely different from each other and the controversies about which of them is better continues to this day.
While the Z80 was seen as a more professional CPU, it could run CP / M, an operating system of the time that is considered the forerunner of MS-DOS. We are not going to discuss here if we are talking about a copy or an inspiration, only that the CP / M was designed to run on the 8080 and its clones, which made computers with this CPU have the ability to run said operating system. .
The 6502 had a different path, it was the CPU used by the first Apple computers and the first Atari computers and consoles. Nor can we forget about Commodore, since after all it was the owner of MOS. Unable to run CP / M because of the 6502, each of these manufacturers created their own software libraries, but they were not very successful beyond games. The only one that managed to stand out was Apple in the early years, but as history tells us they were relegated by the PC.
And what about the graphics and sound? This is where each of the microcomputers differed from each other, as it was possible to identify whether a game was available for a Spectrum, a Commodore 64, an Amstrad CPC or any other computer by how it looked and sounded. This was distinguishable and gave each of them a hallmark of identity, which means that each had distinctive hardware in that pair of respects.
BASIC as a universal language
The BASIC programming language became the universal language in microcomputers for developing programs . And it is that each one of them when starting presented a very simple text editor that served to write code in that language that was then compiled in the same microcomputer to save it in the storage unit. That is why many programs were not stored on cassettes or magnetic discs, but you could find them in magazines and books in the form of written code.
The most famous BASIC dialectic was Microsoft‘s, which was originally written for the Intel 8080 and therefore compatible with the Z80, but it was only used on the MSX platform since other brands used their own interpreter. There were also two versions for 6502 of Microsoft BASIC not compatible with each other, one for Commodore and the other for Apple. All this caused that the platforms were not compatible with each other in terms of software.
Storage unit in microcomputers: the cassette
The cassette was the standard storage unit used in the vast majority of microcomputers. Although it was possible to use magnetic disk drives, as storage drives these were very expensive hardware-wise drives. It was also possible to use cartridges, but being based only on ROM memory they were readable.
Cassettes were ideal due to the fact that they were cheap and it was very easy to write data on them, the units were the same that were used to reproduce commercial tape units, where the classic mini Jack was used as a data bus for communication. Of course, it was very slow and loading the data from the cassette was tedious, so the data was dumped from the cassette to RAM.
It must be taken into account that a tape is a continuous storage unit, unlike a disk unit we cannot search for a specific data in a specific position. So the tape unit was going through and its content in bits was reproduced through the audio output, but with the difference that each of the microcomputers did not interpret it as sound, but as data lines after digitization. that were stored in RAM and once there the program could be executed.
