Plyojump - Computer History
Computer Circuits - a lot of switches
Computers perform logical operations by opening and closing switches. The "1s" and "0s" computers are often said to use are actually the presence or absence of electricity in one of their circuits. Since there is no "2" inside a computer, the "1s" and "0s" are called by a special name - Boolean, which also maps to "TRUE" and "FALSE" in logic.
The logic of these circuits can be written out formally (as when designing a computer chip) using a "truth table" - note the "1s" and "0s" are actually TRUE or FALSE, or the presence or absence of electric current, or whether a switch is open (0) or closed (1).
To make a circuit that does something requires LOTS of these circuits (100s of millions in a modern PC)
What computer circuits are made from
Early electronic computers in the 1940s used vacumn tubes to create logic switches.
The transistor replaced the vacumn tube in the 1950s. Transistors are smaller (can be made VERY small, see rightmost dot in left image), and don't burn out over time. They use silicon to make the switches.Many 1950s computers used hand-wired transistor boards, like the one shown on the right
computer logic realized with vacuum tubes, 1940s
Logic circuits made with large transistors (a digital clock) and part of a computer circuit board. Today's computers still require lots of large transistors to interconnecter the more complex computer chips (see below)
Logic circuits physically realized on a silicon computer chip. The small squares are individual transistors
Computer Hardware Minaturization 1945-2010
Modern electronic computer technology uses logic circuits created on silicon wafers, or "chips", which don't have to be hand-wired. This is accomplished by "printing" the transistors on a single chip of silicon. The process is very similar to traditional stone lithography used in graphic design for centuries.
Images of the first integrated circuit printed on silicon (circa 1960) and the Pentim 4004, the first full computer on a chip (1972)
Image of the Pentium 4 (2000). Each small square in the processor is roughly as complex as the entire 4004 processor. See "Microprocessor hall of fame" for more examples: http://www.tayloredge.com/museum/processor/processorhistory.html
How Integrated circuits are made
The circuits of a chip are too small to create using lasers, robots, or other devices. Instead, they are make by a process similar to classic lithography used by book printers and graphic designers to print images.
Silicon ingots (a single crystal of pure silicon), showing cut wafters, then a wafer during the photoresist process, finally, a wafter being cut into individual silicon chips. Finally, wires are attached ("pins") and the whole chip is encased in plastic to protect it from light
Silicon chips encased in plastic and sodered onto a circuit board. Right, a closeup of the pins from the chip connecting to the boards. Parallel lines on the green board are wires interconnecting the chips. Other objects are individual transistors which must be large since they handle lots of power.
Videos on Computer Chip manufacture
Good technical video showing photolithography
All computers today use a von Neuman architecture
Current computers use a "Von Neuman" architecture, named after John von Neuman, who proposed the design in the late 1940s
- Control Unit - stores the commands of the computer program, and executes them one at a time
- Arithmetic Logic Unit - performs both math and logic calculations
- Accumulator - where results of a computation are stored
- Input - a device that allows information from outside the computer to be sent into the Logic Unit (e.g. data from a webcam or a keyboard)
- Output - a device that allows the results to be sent outside the computer (e.g. to a computer monitor or speaker)
Hardware Versus Software
Under the von Neuman architecture:
- Hardware is the actual electrical circuits used to create a computer
- Software is a list of the order in which switches open an close during computation.
- Computer programs are a specific file holding these instructions (with an .exe file extension under Windows)
Types of Computers - Mainframes
Supercomputer (array of smaller computers)
Internet server computers with 9 or 15 (count them) hard drives. There is no monitor or keyboard, since this computer is always accessed via the Internet.
Internet servers rack-mounted in a data center. Such computers can handle thousands of users per hour. Companies like Google have 25,000 or more of these computers, the equivalent of several mainframes.
Workstations and "Gamer" Computers
Workstation - Scientific and "Gamer" PCs are about the same power/configuration. Prices range from the low thousands to 20,000 or more. These computers typically excel at 3D graphics and fast rendering.
Standard Consumer PCs are similar to workstations, but generally have slower hardware and cheaper video cards. Prices range from a few hundred to a few thousand dollars.
"Low end" consumer PC suitable for word processing and web-surfing (and not much else). They often cannot play 3D games.
The XBox - a specialized low-end PC coupled with high-performance graphics.
TViO, a dedicated low-end, Linux-based PC optimized for video recording and display
Notebook PCs have slow hardware and limited graphics to conserve battery power. They make up for it in portability. Left a Windows portable, right the Apple iBook.
The newest type of portable is the "Netbook" - a very small notebook with very limited onboard storage and no 3D graphics. Netbook users typically use their portables for net surfing and little else. Due to their low power, battery life is generally longer than a notebook.
eBooks are slow portable computers optimized for the display of text. Frequently, they have a special wireless download system (NOT wi-fi) tying them to a specific vendor, in a manner similar to iTunes and Apple hardware. Compared to other portables they have very long (1 week) battery life, since they do not display color images or movies.Propular for people who travel extensively.
Left to right: the Amazon Kindle, Sony eBook
PDAs (Personal Digital Assistants)
Early PDAs (Personal Digital Assistants) from the 1990s - the Palm 5000 and the Apple Newton
Modern PDAs (Personal Digital Assistant), Pocket PC (Dell), Apple's iPhone, Linux-Based
Portable game systems (a PDA with higher-performance graphics)
Smartphones are cellphones with additional features installed, like Internet surfing. Unlike a PDA, their primary functions remains phone calls, and screen sizes are very small
Consumer Media Players
Smaller computers - iPod, and portable DVD player
Single-board computer, similar to the one in your car engine. These computers work behind the scenes, and typically do not require a monitor or keyboard.
SPOT computers are very small systems created by Microsoft to relay data including the weather and stock quotes. Developed around 2002, they have not been successful competing with smartphones and PDAs, and Microsoft plans to "shut them off" in 2012.
Single Microprocessor Computers
Single-chip computers ("Microprocessors") - a kind of very simple embedded computer found in microwaves, video cameras and digital cameras, parking meters, and even cooking knives. Despite their tiny size, they are complete "computers on a chip".