Designing the Z80, By Masatoshi Shima

In this, the the seventh of our Friday series about the early microprocessors, Masatoshi Shima, fresh from the success of designing the 8080, decides to leave Intel. Shima’s friend, Federico Faggin, was preparing to leave Intel to found Zilog to pursue his vision of the next generation of microprocessors, and Shima was anxious share in it.

“There were two reasons to leave Intel to go with Federico,” explains Shima, “first – the 1974 oil-shock – the Intel share price went down from $72 to $18, and I realised I could not make money; second – a microprocessor had come out from Fairchild called the F8 which they positioned as the basis for a two-chip system.”

“Intel decided it wanted to make similar types of products to the F8 – highly integrated microprocessors rather than high performance microprocessors. Federico and I wanted to develop high performance microprocessors – but the Intel management didn’t buy that idea.”

In February 1975, Shima left Intel to join Faggin at Zilog. Faggin had still not got funding for the company at that time; it was to be another four months before Exxon stumped up half a million dollars to back the new company.

Shima headed up the design and development work on the Z80 – one of the industry’s legendary products.

The Z80’s development was completed over thirty years ago, in early 1976. Shima stayed on at Zilog after the Z80 project was finished, to head up the team which defined the architecture and did the design for Zilog’s first 16-bit microprocessor – the Z8000.

“One day my wife asked me to go back to Japan. Our daughters were by then six years old and she wanted to provide a Japanese education for them.”

It was nine years since Shima had left Ricoh, and he could still have gone back there, but “I wanted to do something with LSI”, he says.

Shima’s Silicon Valley friends urged him to talk to Intel who were looking at setting up a design centre in Japan.

So when Shima returned to Japan in 1980 it was as the head of Intel’s Japanese Design Centre. He was to be there for nearly a decade.

Shima left Intel in 1986 and founded VM Technology. The money was put up by Ascii Corporation. Shima has ten per cent of the equity of VM Technology which makes x86 compatible microprocessors.

To Shima, designing microprocessors is God’s own job. “I always wanted to do challenging work – something risky and challenging – that’s the kind of job that makes me happy”, he muses, “in this world you can acquire money, or a great name for yourself, or a rewarding job – but you can’t have all three. Hoff got the name; Federico got the money; but I kept on developing microprocessors – I got the job.”