On our journey through time, Davide Calvi accompanies us of the videogame retroedicola association, better known as Dr. Fix, who tells us unique details and anecdotes on the Cosmac Elf.
The computer that Davide Dr. Fix showed us is a replica of the Cosmac ELF, which he made himself.
The history of the Cosmac ELF and Joseph A. Weisbecker
The Cosmac ELF was conceived in 1976 by Joseph A. Weisbecker, a visionary engineer working for RCA. Weisbecker designed this microcomputer as an educational and accessible medium, publishing it in the journal Popular Electronics. The simplicity of the design allowed enthusiasts to build it themselves, using readily available components.
The heart of the computer was the CDP1802 Cosmac microprocessor, one of the first made of CMOS technology. This microprocessor had exceptional characteristics for the time: low energy consumption, an 8 -bit bidirectional bus, simple but effective architecture and much more.
Not surprisingly, the RCA 1802 was subsequently employed in some NASA spatial missions, thanks to a version made of silicon on sapphire (Silicon on Sapphire).
Cosmac is the acronym for complementary symic monolithic array computer.
Technical characteristics of the Cosmac ELF
One of the most fascinating aspects of the Cosmac ELF was its minimal structure, which allowed users to understand how a computer works on a deeper level. Here are its main features:
- RCA 1802 processor (also COSMAC 1802): an 8-bit microprocessor, in CMOS technology, innovative for its resistance and reliability.
- 256 bytes of static RAM: an extremely small amount by today's standards, but enough for the educational purposes of the project.
- Manual input: This was done via switches to enter data in binary code.
- Visual output: used LEDs and two numeric displays to show the data entered and the results of the operations.
- Expandability: Thanks to additional modules, it was possible to add features such as video output, made possible by the CDP 1861 chip.
The architecture of the Cosmac ELF was deliberately spartan, but this simplicity made it perfect for those who wanted to learn the basics of programming and hardware.
An educational and revolutionary project
The Cosmac ELF represented a revolutionary idea for 1976. At a time when computers were only accessible to large companies or universities, Weisbecker envisioned a platform that anyone could build in their own home. This "do-it-yourself" approach turned the computer into a learning tool.
Dr. Fix points out how ELF has paved the way for generations of enthusiasts and engineers.
Modern replicas of the Cosmac ELF
In recent years, interest in vintage computers has led to the creation of replicas of the Cosmac ELF, which faithfully reproduce the original experience, but with some modern improvements. During the interview, Dr. Fix showed us and described his reply.
The video output was made possible by the CDP 1861 chip. In Dr. Fix's reply it is emulated with modern chips, as the original chip is difficult to find today.
An interesting aspect of the replica of Dr. Fix's Cosmac ELF is the ability to load programs automatically, without manually entering all the binary codes via micro switches.
This balance between past and present makes replicas perfect for both nostalgic people and those who want a little more convenience and speed in data entry.
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