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Throughout this web site, there are multiple references to printed circuit boards, chips, semiconductors, integrated and other types of circuits and electrical componentsSo much so, that I’ve noticed some confusion about how each of these items fit together.  This page is intended to “tie it all together” and make some sense of these terms which are often used interchangeably, but not terribly precisely:

NOTE:  Items highlighted in RED are defined elsewhere in this Glossary, while items highlighted in BLUE are site links for further information. 

THIS IS ONE OF THE PAGES IN THIS SITE WHERE IT IS IMPORTANT TO READ THE HIGHLIGHTED DEFINITIONS FOR MORE INFORMATION!

Let’s start at the beginning, more precisely the bottom.  That would be the BOARD, or printed circuit board or “PCB”.  This is the green silicon-based board on which usually printed some sort of copper circuits and onto which various components are fastened to “populate” it.  (Why green?  Like I said above, go to the glossary definition...)

blank pcb

BLANK PRINTED CIRCUIT BOARDS (“PCBs”)

Inside computers, there may be several different types of boards.  These will vary, of course, by configuration (tower, laptop, netbook, etc.) and components (video, sound, peripherals, etc.).  Among them are:  The motherboard, or main board, onto which all of the components and other boards are attached.  The exact dimensions of the motherboard will be determined by the size of the case in which it is contained (e.g. ATX, mini, etc.)  Also, when other printed circuit boards are attached to the motherboard (usually by sitting them in various types of slots which are permanently affixed to it), they are called “cards” or “riser cards,” which usually fit perpendicular to the main board. These cards expand or add various features of the motherboard, such as video, audio, network connections, telephone modems and the like.  In addition, there are other types of printed circuit boards sometimes incorrectly called “chips” (which will be discussed separately, below).  Common chips would be those affixed on a RAM module,” which is the correct term for that type of riser card.  Finally, various computer components and peripherals have their own internal PCBs as well, like the hard disk drive, CD/DVD, etc.  Some examples are shown below:

riser card
motherboard, full

FULL ATX COMPUTER MOTHERBOARD

ram module

RISER CARD BEING INSERTED

pcb on hard disk drive

RAM MODULE (SHOWING 8 CHIPS)

ram chip in slot

PCB ON HARD DRIVE

INSERTING A RAM MODULE INTO A SLOT

The first step which taken with a blank PCB is to imprint it with CIRCUITS.  This is done by coating the entire board with a substance like copper, then placing a “mask” over the copper which isn’t to be removed, and then “washing” the unwanted copper coating, leaving only the printed copper circuits which will be necessary for the board’s use.  The result looks like this:

pcb with circuits

PCB WITH PRINTED CIRCUITS

It still doesn’t look like much, so there is more to be done.  It has to be “populated”.  The “holes” that you see at the ends of many of the lines of the copper circuit are there so that various COMPONENTS can be attached to the board at those points.  Depending on the engineering design and purpose of the board, these components may include any number of such electronic devices as capacitors, resistors, memristors, transistors, rectifiers, diodes, transformers, thermistors, microprocessors and many other items. Although they are usually attached by soldering, they may also be affixed to the motherboard by other methods like rivets, screws, pins or the like, even glue.

pcb with components

POPULATED PCB

In addition to the components discussed above, boards usually have one of more “CHIPS”.  [Click HERE for the history, derivation and evolution of chips, integrated circuits and semiconductors and HERE for how they operate computers.] There are quite a few types and sizes of chips.  For example, the little black boxes mounted on the RAM module, above, are chips.  The black squares in the photo above are chips, and they are connected to the motherboard via the little wires coming out of the sides of the chip.  The chips like these that are permanently mounted on the board (as opposed to the main processor, which is removable) generally control such features as video and sound (although they can be bypassed and replaced with more powerful riser cards if desired).  The main processor that is mounted on the motherboard with heat sync and a cooling fan is a large and very powerful chip.  It can be mounted in a number of ways, such as soldered, by pins, clips or (most commonly in newer computers) a ball grid array.  See also, ALU, which is now usually part of the processor chip or math co-processor, which was a separate chip in earlier versions.

One type of very small and very powerful chip that is quite common in computers, cell phones, cars and appliances is the SEMICONDUCTOR chip.  This type of  IC chip is a small silicon wafer that contains thousands, millions, even billions (see neural computers) of transistors and other micro-circuitry called “integrated circuits”.  It’s kind of like reducing the entire motherboard and all of its components into something the size of a tack.  See also, MEMS, Smart Dust and nanotechnology, which reduce entire systems into micro size.  They are called semiconductors because of the properties of the material on which the circuits are printed.   Semiconductor chips, usually the processor, which can sometimes contain several cores, are also mounted on the PCB along with the other components.

processor chip in computer

COMPUTER PROCESSOR CHIP INSTALLED IN BOARD SOCKET, WITHOUT THE HEAT SYNC AND FAN WHICH IS USUALLY ATTACHED ON TOP OF THE CHIP

Also, a part of the board circuitry, but not a component, are the input and output ports into which cables from the peripheral devices which will be physically attached or otherwise connected to the PCB itself.  These ports may be cable or wire attachment points (e.g. parallel, serial, PS/2, USB, DIN, video, audio, ethernet, case lights, etc.) or actual ports (for SATA or IDE drives or other peripherals or power, AGP, PCI/PCI Express, etc.), even infrared (“IR”), Bluetooth and wireless connections, depending on their use.  See the example below:

motherboard-labelled5

So what have we learned from this?  First, to identify what’s “under the hood” in a computer’s main circuitry.  Also, that there is some precision that must be considered when speaking about boards, chips, modules, circuits and electronics.  It’ll make repairing and ordering parts for a computer much, much easier, whether you are an expert or a novice.

TO LEARN HOW THESE BOARDS & CHIPS ARE USED TO BUILD A COMPUTER, CLICK HERE. AND FOR HOW TO KNOW IF YOUR MOTHERBOARD IS BAD, CLICK HERE.

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