The Altair 680 is a computer kit from the mid-1970s. It included a Motorola 6800 microprocessor running at 500 kHz.
This is my project to create a fully functional Altair 680 complete with VGA and a PS/2 keyboard driver as well as a UART for connecting a terminal. To download the Verilog source, see my GitHub page. The system was developed using Icarus Verilog for simulation and the GTKWave wave viewer.
If you have a Digilent Spartan-3E development board, the following bitfile can be used for a complete Altair 680 system: altair680.bit. This uses the PS/2 port for a keyboard and the VGA port for the monitor. You can also connect an RS-232 for a terminal (9600 baud, no parity). The button under the knob on the board will reset the system. When started, this will load the PROM monitor and show the "." prompt. Type "J0000" to enter the BASIC interpreter.