The processor in your phone today has billions of transistors. So how many were there at the first step of this journey? The answer: 2,300. And this chip was designed not for a computer but for a calculator.
A calculator order
The story begins in Japan. A calculator company called Busicom asked Intel for custom chips for a new desktop printing calculator. In those days it was normal to design many different custom chips for such a device.
The team at Intel chose a different path: to gather the computation on a single general-purpose processor chip. That chip was named the 4004. Four names stand out in its design: Federico Faggin, Marcian "Ted" Hoff, Stanley Mazor and Masatoshi Shima of Busicom.
The Intel 4004 was announced on November 15, 1971 with an Intel ad in Electronic News magazine. The first commercial product to use the chip was Busicom's 141-PF printing calculator.
The 4004 in numbers
According to the technical data on Wikipedia, the 4004:
- contained 2,300 transistors,
- ran at a clock speed of at most about 740 kHz (the target was actually 1 MHz),
- was made with a 10-micrometer silicon-gate pMOS process,
- worked with 4-bit data and came in a 16-pin package,
- cost $60 at launch.
A single instruction cycle took 10.8 microseconds. Its speed was roughly between 46,000 and 92,000 instructions per second, depending on whether instructions took one or two machine cycles. It sounds like very little today, but for a single chip to carry the whole "brain" of a calculator was a big leap at the time.
What does "4-bit" mean? At each step the chip could work with only 4 bits, that is, a number between 0 and 15. That was enough for a calculator working with decimal digits (0 to 9); bigger numbers were processed piece by piece over several steps.
From 1971 to today: how many times over?
For comparison, let's look at a current phone chip. Apple's A17 Pro chip, announced on September 12, 2023 and used in the iPhone 15 Pro and iPhone 15 Pro Max, contains 19 billion transistors according to Wikipedia and is built on a 3-nanometer process.
Let's do a simple division: 19,000,000,000 divided by 2,300 is about 8.26 million. So in a little over half a century, the number of transistors on a single chip in our pocket has grown about 8 million times compared with the first microprocessor.
The difference in manufacturing process is striking too. The 4004's 10-micrometer process corresponds to 10,000 nanometers. Compared with the A17 Pro's process called "3 nm", that is a difference of thousands of times. (Let's also note that today's "nm" names no longer correspond one-to-one to a single physical measurement, but are more of a generation label.)
| Intel 4004 (1971) | A17 Pro (2023) |
|---|---|
| 2,300 transistors | 19 billion transistors |
| At most ~740 kHz | At most 3.78 GHz |
| 10-micrometer process | "3 nm" process |
| 4-bit | 64-bit |
| For a calculator | For a smartphone |
Small chip, big idea
This growth even has a name: "Moore's Law", based on an observation by Gordon Moore, one of Intel's founders. It isn't a law of nature; it's an observation, and an industry target, that the number of transistors on chips doubles at regular intervals. The line running from the 4004 to the A17 Pro shows what a powerful compass this observation has been for half a century.
What made the 4004 important wasn't its raw power. The real revolution was showing that a processor could fit on a single chip and be programmed for different jobs. In the following years this idea paved the way for personal computers, game consoles and eventually smartphones.
Everything that comes to mind today when we say "processor", the idea of a single chip that runs software and behaves accordingly, became concrete in this small black part. Busicom's calculator isn't much remembered today, but the chip inside it is.
A project that began as a calculator order stands at the head of the family tree of nearly every electronic device we use today.
The transistor count has grown millions of times in half a century; do you think we can predict today what will change in chips over the next 50 years?