The Rockwell 920 calculator coming all the way back from the 70s was said to be a pretty impressive piece of hardware for its time.
The Rockwell 920, reviewed by Amen, it actually showed a 16-digit display, a new printer, and it could also run programs at the same time! According to the story by Hackaday, it was even equipped with a magnetic card reader/writer capable of being used in order to store some programs as well as data externally.
When looking at it today, it was maybe less like a computer and actually more like what could be called a particular single-board computer for the Rockwell 920. They are also reportedly a windom directly into another era. This was a time when a lot of electrical design assumptions that had now been taken forgranted hadent happened yet.
When the final time would come to finally dig into exactly what made the particular calculator tick, Amen reportedly had a lot of different work to do just to be able to get some basic tools running. An example of this is Amen’s Blue Pill, which is known as a sort of open-source, multipurpose test as well as measurement tool, is, on one hand, actually a perfect tool to be able to snoop up the inner workings.
Rockwell 920 vintage calculator
However, the said inner workings of Rockwell 920 happen to use the negative logic set at -17V which could then mean a logical zero at -17 and a one is also 0V. It also uses an oddball clock rate for initial booting. Since the said Blue Pill doesn’t really support the -17V negative logic, there might still need to be a bit of custom work in order to craft an interface.
The unfamiliar elements, however, didn’t really end there. The pins on each IC, as an example, are in quite a staggered layout which is quite unlike the whole DIP pattern that most people are familiar with. As for the said processor itself, Amen already has access towards low-level documentation on the Rockwell processors as well as instruction sets, but the whole timing diagrams are still puzzling until one would realize that the processor itself has two different clock inputs at two different frequencies. This results in what Amen describes as four different “clock phases.” Check out how the Rockwell 920 calculator was dissected and inspected.
Of course modern technology has already advanced quite a bit and while those that aren’t particularly that interested in tinkering with the engineering, the programming side can be quite interesting still. The Intel i9 computer is a good piece of hardware for those into programming. Another reasonable alternative would be the new MacBook Pro with M1 chips..
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