the reader about the physical and electronic part of a computer. You should be ready to build a computer right after you read this but I recommend finding somebody that has built one for a reference.
First off were going to talk about lab safety. But make sure you come back and read this after you fry yourself because you forgot that you weren't supposed to touch that red wire in the monitor!..
TOP TEN LIST TO PERSONAL SAFETY
- Do not work alone.
- Wear non-conducting shoes.
- When working around A/C work with one hand in pocket.
- Never assume a system is safe to work on.
- Usually work with computers plugged in and monitors plugged out.
- Never wear jewelry.
- No loose clothing.
- Don't connect or disconnect peripherals when the system is on. (unless you have usb ports)
- Use only c, bc, or abc, fire extinguishers.
- Always discharge compositors before touching.
Now I will tell you why you should abide by these rules.
- The reason you should not work alone is because you can get easily hurt and/or shocked and your computer can possibly catch on fire and a second person can help greatly.
- The reason you should wear non-conducting shoes is because conducting shoes keep electric static which could possibly fry your computer or yourself.
- Rule number three, is just because if the A/C shoots volts down through your body it should stop at the hand in your pocket will keep you insulated.
- Never assume a computer is safe to work on because a lot of the time it's not. If you follow all rules it should be safe though.
- The reason you should keep your computer plugged in is because most computer plugs have a third prong on it which is a ground and if volts do happen to shoot down the cord it will stop at the ground.
- Never wear jewelry, ESD (electric static discharge) and jewelry don't mix.
- Don't wear loose clothing because your clothes can get caught on something and could make it fall and/or break or something to that nature.
- Unless you have usb ports, you can fry the controller or slot if you plug the cord in or out while the computer is on.
- Notice that all the three different types of fire extenguishers have a "c" in them. This means that it will not hurt your computer because the c has some chemical in it that should keep your computer safe if you have to use a fire extinguisher on it.
- Capacitors can have 20,000 volts in them even if the computer is turned off!! Common sense says discharge first!
Enough of personal safety now to the important part. In the words of my computer teacher. "If this place catches on fire make sure you get all the equipment out first!!!" Mr. Butler.
- Static mat .
- Wrist strap.
- Keep all components in anti-static bag.
- Individual chips should mount in a special non-static bag.
- Handle all parts by their edge. Do not touch metal parts or chips.
- You should always follow rules 1 and/or 2. If you do not, it's very possible that you could fry yourself or your computer.
- look at number 1)
- If you kept the part in an anti-static bag then when you insert it into your computer it should have no electronic charge and same goes for rule number 4.
- look up to rule number 3
- The reason for this rule is because 30 volts can fry a chip and you body can feel from 2,500 volts up. So you may fry a computer chip and it not even shock you.
There are three major cases in a computer which you might want to know about. One is called an at case which means that the standard for the at case has a two plug supply to the motherboard, a keyboard, and peripheral slots all in standard locations. The second type case is an atx case which has one plug supply to the motherboard, keyboard, com ports, printer ports, and usb ports all in standard locations. The third type is a proprietary case which means there is no standard for what's on it and where they attach. There are four major styles of cases. The first one is a tower and it stands upright and is what most computers are made in now. Their's also desktop, slimline, and proprietary too, but mostly just towers.
A motherboard is what everything plugs into, and without one you can't do much with your computer. It is what I would call the most important part of your computer.
There are three major types of motherboards. They are at, atx, and proprietary. You will only mostly deal with at and atx. There are four main buses on the motherboard. They are power bus, address bus, data bus, and a control bus. A bus is a bundle of wires that send info through them.
Microprocessors are what we would call brains. They think for the computer and most info except for DMA (direct memory access) goes from application etc.. to CPU and then to memory. Most modern CPU chips have 8 registers on them. They are data, address, accumulator, program counter, instructions, flag, alu, and a fpu. Registers are storage places for data, numbers etc… the program counter stores the addresses of the next instructions to be done. The instruction register holds the current instruction. The address register contains memory addresses of the current instruction. The address register contains memory address of the next read or write. The accumulator holds one of the mathematical data to be used or the answer to the previous operation. Data registers hold the second part of the mathematical data for the current operation. Flag registers are special bits that are set individually by certain instructions. That's an into to what is inside the cup. FYI - the wires inside a CPU are smaller than a centimeter. The reason the chip is made so big is so that we can handle it.
HISTORY ON COMPUTER
About the first in home computer made by Intel was an Intel 8088 with a 8 bit data bus, a 20 bit address bus and a 16 bit register. Next inline from Intel was the 8086 with a 16 bit data bus and a 20 bit address bus. Then a 80286 with the same thing as the 8086 but a 24 bit address bus. Then their was a 80386 SX with a 16 bit data bus, 24 bit address bus and a 32 bit register. Next was the 80386 DX with a 32 bit data bus, a 32 bit address bus, and a 32 bit register. Then the 80486 SX with the same as the 80386 DX but a little faster. Then Intel came out with a 80486 DX and also a built in FPU. (floating point unit) What the FPU did was let the CPU be able to do decimals super fast which enabled 3D games to run super fast. Next was the 80486 DX2 which was twice as fast as the 80486 DX, and after that came the 80486 DX4 which was three times as fast as the 80486. Then they introduced the Pentium chip. The Pentium chip had a huge 64 bit data bus, a 32 bit address bus and a 32 bit register. It is estimated that every 6 months technology doubles. So as technology advanced computers will get even faster. (I cant imagine needing anything bigger than my 400 MHz) Hope that didn't bore you do death.
Since most people are familiar with such things as a CD-ROM drive. I wont go scrutinize about hard storage. I will just briefly cover it. Most computers typically have a 3 ½ floppy drive, usually assigned to drive letter A. what a lot of people do not know is that there is 3 types of 3 ½ floppies. There is a double density that formats to 720 kb. Then they came out with a high density disk that formats to 1.44 Mb which is twice as much as the double density disk. After the high density disk came the super density disk which formatted came to 2.8 Mb which as you might have guessed is twice as much as the high density disk. There is also a zip drive that holds 100 Mb's of space but not everybody has one and since a zip disk wont fit in a 3 ½ floppy drive and with the creation of the LS-120 disk which holds 120 Mb and 3 ½ floppy's can fit in LS-120 drives I predict zip drives wont really ever take off. Now about CD-ROMs. There is two major types of CD-ROMs out right now. One is scsi CD-ROM. Scsi cards are usually cheap and if you ever find a CD-ROM out somewhere that is fairly new and very cheap then odds are it is a scsi. The reason they are cheap is because they don't run by their self, u have to have an adapter to go with it and that adapter costs about 50 bucks and most people don't know that when they buy the scsi and that's how scsi sellers make their money. Another brand is ATAPI. ATAPI CD-ROMs plug into the IDE slot and then once plugged in you will have to install the CD-ROM driver and translator and it should work if you use the right driver. There is more proprietary CD-ROM's but most of them plug into the sound card and that can cause problems so I would stay away from scsi and proprietary and go with ATAPI.
Every hard drive must be partitioned and formatted before they can be used. You will need a copy of a partition too. At this time fdisk is a good partitioning too. Read the manual that comes with it and it will tell you how to use it. Dos partitions are super easy to make.
INTERRUPTS, DMA's AND IRQS
An interrupt is just like it says, it interrupt's something. I'll give you an example of how it works. Say your in school and your teacher is giving a lecture and somebody raises their hand and the teacher stops the lecture and asks the student what his question is. That is just like a computer interrupt. Lets say that you were connected to the internet. You type in a URL to go to www.techtweek.com and your modem sends out the data to all those DNS servers and then when a DNS server finds the address www.arshadaliansari.com.com it will send back the information to the modem. Well the modem cant hold all of that info and has to send it to the memory so the modem can get some more info. But first it has to get the attention of the CPU so the CPU can put the info into the memory. So it uses it's interrupt to do this. It sends out a signal saying "hey I need you" (not really but close enough) and the computer sends back to the modem "go ahead and tell me what you need" and then the modem asks where it can store it's info in memory and then the CPU gives it the address to store the info at. Then the modem sends info to the memory using DMA. (direct memory access) DMA means that it can access the memory directly without having to go through the CPU. But sometimes it might have to go to the CPU once just to know where to put the info it has into memory then it can access the memory without any help. So now you know what an interrupt is and what DMA is, but what is an irq? An irq is the order of interrupt assignments in which the accer in. On older computers their was only 8 interrupts
- 0) available
- 1) sound/available
- 2) floppy disk controller
- 3) available
- 4) first DMA Controller
- 5) sound/available
- 6) available
- 7) available
so 0, being the first interrupt and 7 being the last. Now on the newer computer's there is currently 16 irq's.
- 1) system timer
- 2) Keyboard controller
- 8) Real-time clock
- 9) Available
- 10) Available
- 11) Available
- 12) Motherboard mouse port/available
- 13) Math coprocessor/available
- 14) Primary IDE
- 15) Secondary IDE/available
- 3) Serial port 2
- 4) Serial port 1
- 5) Sound/parallel port 2
- 6) Floppy disk controller
- 7) Parallel port 1
This might look out of order but this is the way they come in. I'll explain what this means and how it works now. Lets say you were moving your mouse. Your mouse is irq number 12. Every time you move your mouse it sends out an interrupt 12 to your CPU and says, I need u! Then the CPU will reply back "what do you need" and then the mouse will say, "where am I on the screen and the CPU will tell it "you in position dah dah dah." That's how the irq works, well lets say that your moving your mouse while using your serial port 2. Your mouse has priority over your serial port 2 because your mouse comes first on your irq list. So when your sitting their just swishing your mouse around making a figure eight on your computer, you could be interrupting a function that your computer is doing and it will slow it down a tad.