Make your own ALTAIR computer based on an Arduino
Designed by Ed Roberts and released in 1974, the MITS ALTAIR sparked the personal computer revolution and was the basis for Microsoft's first product, the Altair BASIC interpreter. It cost $439. While ALTAIR replica kits and online emulators have been available for years, there's now a $149 kit that substitutes the ALTAIR guts with an Arduino Due while duplicating its iconic LED-laden case. From Stephen Cass's review of the Altairduino at IEEE Spectrum:
The Altairduino is derived from David Hansel's work on cloning the Altair with the Arduino Due and Arduino Mega 2560. If you want to build one of Hansel's designs from scratch, you can do so by following his free instructions on hackster.io. The advantage of Davis's kit is that it provides all the components, including a nice bamboo case and plastic front panel, along with a custom printed circuit board (PCB) that greatly simplifies construction.
The Altairduino improves on the original Altair in two important respects. First, it offers modern interface options. You can connect an old-school terminal using an optional DB-9 connector (which I will stipulate should properly be called a DE-9 connector, so no need to send me letters this time!), but you can also use a soft terminal running on a computer via a USB connection, or even Bluetooth....
The second big improvement is that the Altairduino comes loaded with a lot of software. You can call up some programs purely by flipping various front panel switches, such as Kill the Bit, a game that hacked the Altair's memory-address indicator lights to act as a 1-dimensional display. Other programs are called up with a combination of switch throws and terminal commands. You can quickly fire up Microsoft's very first 4-kilobyte Basic (which gives you the option, on startup, to disable its sine, random number, and square root functions to save a little memory), or its more advanced 16-KB Basic. The latter has a number of programs you can load from the Altairduino's memory, including early computer game classics such as Lunar Lander, Star Trek, and Hunt the Wumpus.
"Build Your Own Altair 8800 Personal Computer" (IEEE Spectrum)
(gif by Randi Klett)