2 years ago they wrote about a home-made computer with a processor on separate integrated circuits - BMOW1 . From an architectural point of view, it was very advanced, but extremely difficult to repeat.

The author of BMOW1 (Steve Chamberlin - Steve Chamberlin) has developed a Nibbler computer , consisting of only 17 chips. Moreover - the processor there is also assembled on discrete logic.

Well, let's see what's inside.

Architecture

Nibbler - 4-bit processor. 2 ROMs are used to store microcode, 1 ROM for command memory - 12 bit address, 8 bit command.
RAM - 12 bit address, 4 bit data. Arithmetic is considered standard ALU 74181 (our analogue of K155IP3).

Nibbler communicates with the outside world through a speaker, a standard HD44700 LCD text screen.

The clock frequency is 2 MHz, each command takes 2 clock cycles. Of course, the inability to write code to the memory imposes serious restrictions on the complexity of programs - but you have to sacrifice something to simplify the design. In addition, it is impossible to read / write memory at an arbitrary calculated address - because corny there are no registers of the required length.

A rare case when a computer circuit fits on one screen:

Design

Like BMOW, Nibbler is assembled by twisting wires, not soldering.


Compared to its predecessor:

Work video

I think it’s quite possible for everyone to assemble such a computer from discrete elements without spending half their life on it :-)