Co-designer of the world's first microprocessor, the Intel 4004, Shima worked alongside Federico Faggin, Ted Hoff, and Stanley Mazor on that landmark achievement. He studied organic chemistry at Tohoku University in Sendai, Japan. With poor prospects for employment in the field of chemistry, he went to work for Busicom, a business calculator manufacturer. There, Shima learned about software and digital circuit design.
When Busicom decided to use LSI circuits in their calculator products, they approached the American companies Mostek and Intel for manufacturing help. The job was given to Intel, which back then was more of a memory company and had facilities to manufacture the high-density silicon gate MOS chip Busicom required. Following Marcian "Ted" Hoff's initial conception, he designed the 4004 processor at the Intel offices with Hoff and Federico Faggin. His company then sold the rights to use the 4004 to Intel, with the exception of use in business calculators.
Intel then designed the 8008 on their own, but the chip was a commercial failure due to various reasons. Shima was then employed to implement the transistor-level logic of Intel's next microprocessor, which became the Intel 8080. He was not involved in the creation of the 8088 and 8086. He moved to Zilog in 1975 and, using only a small number of assistants, developed the transistor-level and physical implementation of the Z80, which Faggin had made instruction compatible with the Intel 8080. This was followed by the same task for the 16-bit Z8000.
According to co-workers from Intel, Faggin's method was to design all logic at the transistor level directly and manually — not at the gate and/or register level. The schematics were therefore hard to read, but as transistors were drawn in such a way that they suggested a "floorplan" of the chip, it actually helped when making the physical chip layout. However, Shima stated, the logic was first tested on breadboards using TTL chips, before being manually translated into MOS transistor equivalents.
He was awarded the Kyoto Prize for Advanced Technology in 1997. The Kyoto Prize is similar in intent to the Nobel Prize.
