Design activity — constructing an artifact description satisfying given
goals and constraints — distinguishes humanity from other animals and
traditional machines, and endowing machines with design abilities at the human
level or beyond has been a long-term pursuit. Though machines have already
demonstrated their abilities in designing new materials, proteins, and computer
programs with advanced artificial intelligence (AI) techniques, the search
space for designing such objects is relatively small, and thus, “Can machines
design like humans?” remains an open question. To explore the boundary of
machine design, here we present a new AI approach to automatically design a
central processing unit (CPU), the brain of a computer, and one of the world’s
most intricate devices humanity have ever designed. This approach generates the
circuit logic, which is represented by a graph structure called Binary
Speculation Diagram (BSD), of the CPU design from only external input-output
observations instead of formal program code. During the generation of BSD,
Monte Carlo-based expansion and the distance of Boolean functions are used to
guarantee accuracy and efficiency, respectively. By efficiently exploring a
search space of unprecedented size 10^{10^{540}}, which is the largest one of
all machine-designed objects to our best knowledge, and thus pushing the limits
of machine design, our approach generates an industrial-scale RISC-V CPU within
only 5 hours. The taped-out CPU successfully runs the Linux operating system
and performs comparably against the human-designed Intel 80486SX CPU. In
addition to learning the world’s first CPU only from input-output observations,
which may reform the semiconductor industry by significantly reducing the
design cycle, our approach even autonomously discovers human knowledge of the
von Neumann architecture.