Popular Electronics was famous for the article introducing the Altair 8800 back in 1975 (well, the cover date was 1975; it really came out in late 1974). That was so popular (no pun intended), that they ran more computer construction articles, including the SWTPC 680 late in 1975. But in 1976 a very popular article ran on building a very simple computer called the COSMAC ELF. [Youtubba] had an Altair, but always wanted a “cute” COSMAC ELF. Now, forty-something years later, he finally got around to it. He made the very detailed video about his experience, below.
Surprisingly, he didn’t have to look very hard for too many of the components as most of them were available from Digikey. He had to get compatible RAM chips, the 1802 CPU and LED displays. He also couldn’t find a look-alike crystal, so he used a fake one and a hidden oscillator. The result looks awfully close to the original. He even did a nice front panel using Front Panel Express.
It might be hard to understand why people got excited over a little computer with a handful of switches. Consider the Altair, though. For $439 you got a very basic machine with 256 bytes of RAM (upgradable to 1K, or beyond if you bought more boards). If you wanted to expand it to something really useful with RAM, disk drives, and a terminal you were still talking lots of cash. And that was 1975 cash. In equivalent terms, that Altair kit would cost $2000 today.
The ELF, on the other hand, could be put together on a piece of perf board. If you had to buy everything from scratch, it might cost $100 back then. If you had a well-stocked junk box, you could cut that down a good bit. The DMA onboard the 1802 chip made the front panel simple, and it facilitated a companion graphics chip that produced crude black and white graphics on a monitor or TV.