A bit in a spreading signal. See chip rate
(C.H.I.P.) World's first $9 computer. See C.H.I.P.
recipitation) A test of the interaction between the DNA and proteins in a human cell. See ChIP on chip
rogram) See healthcare IT
ome over IP
) See Project CHIP
A set of microminiaturized electronic circuits fabricated on a thin slice of semiconductor material. The most amazing technology, the chip is the driving force in this industry, and it resides in nearly every electronic device on the planet. Officially an "integrated circuit" (IC), unpackaged ICs look like tiny "chips" of aluminum. While most chips contain only digital circuits, some are analog only, and some are mixed analog and digital (see mixed mode
). Billions are made every year, and the various types are described below.
Raw chips are approximately 1/30" thick and from 1/32" square to the footprint of a postage stamp and sometimes larger. The primary element in a chip is the transistor, and small chips contain tens of thousands, while large chips have billions. It is actually only the top one-thousandth of an inch of a chip's surface that holds the active circuit layers, and the action that takes place every second is truly unbelievable (see active area
). Although chips may be formed from other materials, silicon is the primary element (see silicon
). To learn how the chip is made, see chip manufacturing
Types of Chips by Function
General-Purpose Logic (CPU)
The central processing unit (CPU) is the primary logic chip in every computer or computer-based device. Also called a "microprocessor," the CPU follows instructions in software and thus can perform countless different tasks. If there is no CPU in a device, it cannot really be called a computer. See CPU
A special-purpose "application specific IC" (ASIC), performs a fixed set of steps that cannot be changed. ASICs are smaller and faster than microprocessors and less expensive but only when manufactured in large volume. See ASIC
Partially Fabricated Logic
All logic chips start out in a semiconductor fabrication facility. However, there are logic chips that are only partially finished at the plant and programmed to completion by the customer, who becomes the circuit designer. See PLD
Flash Memory and RAM
Flash memory chips store data permanently and are used for storage and firmware. RAM chips store data temporarily and are the computer's main memory. RAM is either dynamic (fast) or static (faster), but both are volatile and lose their content without power (see dynamic RAM
and static RAM
). See RAM
, flash memory
, early storage
and early memory
Graphics Processing Unit (GPU)
Executing billions and trillions of calculations per second, the GPU converts the digital images in the computer into pixels for the screen. High-end GPUs are required for gaming PCs in order to render fast video sequences in a realistic manner. See GPU
An MCU is a single chip that contains the CPU, flash storage, RAM, input/output control and a clock (pulse generator). Billions are used every year in myriad products. See microcontroller
An SoC is an MCU and more. For example, in a smartphone, the SoC includes all the MCU components along with a GPU, image processing section and neural processing unit. See SoC
Analog/Digital and Signal Processing
"A/D converters" and "D/A converters" convert real signals (audio, video, voltage, etc.) to the digital world. A related chip is a "digital signal processor" (DSP), which performs fast instruction sequences commonly used in such applications. See A/D converter
, mixed mode
How the Chip Came About
In 1947, the semiconductor industry was born at AT&T's Bell Labs with the invention of the transistor by John Bardeen, Walter Brattain and William Shockley. The transistor, fabricated from solid materials that could change their electrical conductivity, would eventually replace the bulky, hot, glass vacuum tubes used as electronic amplifiers in radio and TV and as on/off switches in computers. By the late 1950s, the giant first-generation computers gave way to smaller, faster and more reliable transistorized machines. See transistor
Drs. Bardeen, Shockley and Brattain
This photo of the three inventors was taken in 1947. (Image courtesy of The Computer History Museum, www.computerhistory.org)
The original transistors were discrete components; each one was soldered onto a circuit board to connect to other individual transistors, resistors and diodes. Since hundreds of transistors were made on the same silicon wafer and cut apart only to be reconnected again, the idea of building them in the required pattern to begin became the goal. In the late 1950s, Jack Kilby of Texas Instruments (TI) figured out how to make capacitors and resistors from the same semiconductor material. Subsequently, Kilby, along with Robert Noyce of Fairchild Semiconductor, created the integrated circuit, a set of interconnected components on a single chip.
Since then, the number of transistors that have been put onto a single chip has increased exponentially, from a handful in the early 1960s to millions by the late 1980s. Today, billions of transistors take up less space than the first transistor. See integrated circuit
From Tube to Transistors in a Chip
LOGIC AND MEMORY
Today, several trillion transistors would fit inside the first computer tube. The byproduct of miniaturization is speed. The smaller the transistor, the faster it switches. See active area
In first- and second-generation computers, internal main memory was made of such materials as tubes filled with liquid mercury, magnetic drums and magnetic cores. As integrated circuits began to flourish in the 1960s, design breakthroughs allowed memories to also be made of semiconductor materials. Thus, logic circuits, the "brains" of the computer, and memory circuits, its internal workspace, were moving along the same miniaturization path.
By the end of the 1970s, it was possible to put a processor, working memory (RAM), permanent memory (ROM), a control unit for handling input and output and a timing clock on the same chip.
Within 25 years, the transistor on a chip grew into the computer on a chip. When the awesome UNIVAC I was introduced in 1951, one could literally open a door and walk inside. Who would have believed the equivalent electronics would some day fit within the head of a pin. No exaggeration (see microcontroller
To learn how the chip is made, see chip manufacturing
. To understand how circuits process data, see Boolean logic
Transistors to Gates to Circuits
Acting like an on/off switch, the transistor is the main component in a digital circuit. Patterns of transistors make up gates, and patterns of gates make up circuits. This shows a mechanical depiction of a half-adder circuit, which adds one bit to another.
Although still highly conceptual, this diagram shows more detail of the half-adder circuit above. This depicts the interconnections of only seven transistors, which are implemented in mulitple layers on the chip. Imagine how complicated today's chips really are that contain billions of transistors in an area no larger than a postage stamp. See half-adder