EMMA HS1 Outline Week #6
Review Homework- Logic Gate Exercises Quiz Online
Computer Cases
Expandability
Getting Your Hands in There
Protection
Longevity
Switches
Power
Reset
Keylock
LEDs
Power
Hard Drive
Case Styles
Desktop
Slimline
Tower
Full Tower
Mid Tower
Mini Tower
Form Factor
AT
ATX
Mini ATX
Micro ATX
ESD – Electrostatic Discharge
How Much is Too Much
ESD and Your Computer
ESD Damage
Immediate Failures
Latent Failures
Antistatic Wrist Straps
Antistatic Mats
What Else?
Handouts – Your Computer’s Case
ESD – Electrostatic Discharge
Homework - Online Case and ESD Quizzes
Your Computer’s Case
Your computer's case plays a large part in the overall expandability, protection, cooling and lifetime of your system.
Expandability
At one time or another you may decide to add something to your computer, such as a DVD Player, a second Hard Drive, a Memory Card Reader, or a Tape Drive. These fit on shelves in your computer called Bays. If there are no extra bays, then there’s no place for these devices to go. These bays can be 3.5 inches or 5.25 inches wide. There are internal and external bays. You can notice the external bays by looking at the front of your case.
Devices like Memory Card Readers and DVD drives slide into external bays and can be seen (and accessed) from the front of your system case. If you have unused bays, they will have a plastic faceplate over them (or at least they should have). If you see that you have empty external bays, then you know that at least there's room to add another of this type of device. Remember however, that hard drives are sometimes hidden behind these faceplates, so a look inside the case will tell you for sure. Hard drives are generally situated in internal bays because there is no need for physical outside access. You must look inside the case to see if you have any free internal expansion bays.
Any device added to your system requires power, and your power supply has to have enough juice to supply that power. If you have a 150 or 200-watt power supply, your system may be limited to the amount of devices that can be added. Most cases come with a power supply, but make sure.
Getting Your Hands in There
You may at one time or another, have to remove, change or check a device in your computer. You want to be able to access that device without too much difficulty. It would be nice if you didn't have to remove the ribbon cables and expansion cards just to install another memory module, or replace a battery. Or, if you're the type that likes to just jam his hand in amongst all that stuff, it would be nice to be able to remove it without accidentally loosening or removing other connections.
On some cases you can loosen a single screw, and completely remove the drive bays for easy access to the drives and their mounting screws. Others have access ports for the screws on the back plate of the case. However, I’ve seen some drive bays that are spot-welded in place without access ports, and you just about have to remove the motherboard to access the screws for the drives. Think about what you want to put inside and make sure there's enough room for access.
Protection
A good, rigid, well built case can protect the internal components from dust, vibration, foreign objects, ESD (Electro Static Discharge) and EMI. Electromagnetic interference is not always an easy one to nail down. My computer has a good solid case, but when you watch TV, you can tell if the computer is on or not.
You can find cheap cases that fit together so poorly, or are so flimsy, that they actually rattle when the computer is turned on. One thing that can be bad for your system are vibrations caused by outside sources; whether it’s a panel or cover that rattles, a desk drawer being closed, or a printer that doesn’t operate the smoothest. The stability of the case makes a big difference.
Some of the case frames are left unfinished, resulting in sharp edges, burrs and metal slivers. Ribbon cables and wires (and your fingers) can be nicked or cut by these sharp edges just by removing or replacing the outside cover. Companies that actually put some research and development into their product will address these issues. You should think about them when you purchase. As with just about everything, you usually get what you pay for.
Longevity
Heat shortens the life of electronic components. The different devices and components inside your case need room to breathe and release heat build-up. Sometimes, things are packed so tightly inside your system case that you can’t even get your hand in to remove a cable or an expansion card, let alone allow for any kind of air flow. Air flow is needed to cool down the components and devices inside the case.
The cooler that your computer operates, the longer it will last. The fan on the power supply is made to help cool the power supply as it operates. The way the case is built should allow the intake of cooler air through vents, draw it over the different components inside to help cool them, and push the heated air out. Some cases come with auxiliary fans that fit over the intake vents to add to the airflow inside.
It’s important not to interrupt this flow. Don’t pack things around the case or obstruct the intake vents. Keep the intake vents clean and clear of grime and dust balls. Also, by leaving the expansion slot inserts off the back of the case, or the faceplate off unused external bays, you could possibly be changing the way the air flows through your case and reducing cooling efficiency.
If you have a system that seems to run fine, then just shuts itself off after a half hour or so, check out the operating temperature of the CPU. See that the fans are working on the power supply and the CPU's heatsink.
Switches and LEDs
If you look at the front of your case you can see the devices that are installed in the external bays and get an idea as to how many unused bays you have. You will also notice one or more switches and LED lights.
Power switch
To start your computer, you have to turn on the power supply. At one time, the power switch for your computer was on the power supply itself, and you had to reach around to the back of your computer to turn it on and off. This was inconvenient, troublesome, and a real pain in the …neck. Most cases today have a remote power switch on the front of the case.
Reset switch
When you first start your computer, it goes through a series of self-tests (POST - Power-On Self Test) before it actually initializes itself and starts up the operating system. The reset switch performs the same function as a warm boot (ctrl+alt+del) which restarts your computer with an abbreviated version of POST, taking a little time off the startup process. With Win95/98’s restart option on the Start menu, today’s computer cases may or may not have a reset switch.
Keylock switch
Most new cases don’t have a Keylock switch. By inserting and turning a key in this lock, you could shut off access to the keyboard, thus denying unwanted users from accessing your computer or preventing an accidental keystroke from interfering or interrupting a currently active program. These are still found on network servers.
Power LED
This light tells you when the power is on to your computer.
Hard Drive LED
This light will go on, or flicker, every time your hard drive is written to or read from. It lets you know whenever the hard drive is being accessed.
Each device installed in a case’s external drive bay (floppy drive, CD-ROM, tape drive, etc.) will usually have its own indicator LED on the front bezel that will come on or flicker when that device is being accessed.
The back of your computer will have holes and slots cut into the frame. These holes allow for the back of expansion cards and any I/O ports that your external devices can plug into. Any slot or hole that is empty should have a cover on it. These are easy to distinguish from any venting holes that might be on the back of your case (venting holes should not be covered). The back of the power supply will also be exposed here showing you the power supply fan vent and the plug for the power cord.
Case Styles
Basically, there are two different styles of system cases today; The Desktop and the Tower.
The desktop case sits flat on the top of your desk with the monitor situated on top. This was the style of IBM's original PC, XT and AT models. These early desktops were fairly large and bulky, taking up a lot of real estate on the desk. The obvious trend was for manufacturers to make them smaller and more compact. Unfortunately, as you make the case smaller, things inside get a little crowded. Access to the different components becomes much more cramped, cooling is a lot less efficient, and there's less room for expansion. Desktops usually have two or three external drive bays and 1 or 2 internal bays.
The slimline case is even smaller. It's shorter, narrower, and looks a lot less bulky on your desk. This is about the only appeal these machines may have. Slimline computers are very proprietary, not well cooled at all, and have about zero room for expansion. Slimlines usually have one or two external bays and one internal.
The tower case sits on end, taking up less square area space and offering a better variety of sizes than a desktop. It allows for a lot more choice as to location, depending of course on the particular size. It can sit on the desk beside the monitor, on a separate shelf, or on the floor beside the desk. On the negative side, it should be mentioned that cases on the floor may be more prone to kicks and bumps and in some locations the cords may have to be extended. Tower cases have much better air flow, better accessibility to internal components, and (except for the micros and ultra low end models) allow for more upgrade and expansion capability.
Full Tower
-largest, up to 36" high
-sits on floor
-larger power supplies, 350 watts or more
-may have 2 X 3.5" and 4 or more 5.25" external bays
-may have 4 or more internal drive bays
-very roomy inside, better cooling
Mid Tower
-power supply - 200 - 300 watts
-quite popular size
-approx 17-20 inches in height
-2 X 3.5" and 3 X 5.25"external drive bays
-2 or 3 internal drive bays
-less room than a full tower to work inside
-still cools really well
-still room for expansion
Mini Tower
-very popular size
-smallest of the tower cases (...sub-mini and micro?)
-can be less than 14 inches high
-power supply 200 to 250 watts
-cools better than a desktop case (but not much)
-2 X 3.5" and 2 X 5.25" external drive bays
-1 or 2 internal drive bays
-a little cramped inside
Note: The sub-mini and micro size cases are actually smaller than the mini tower. These cases have 1 or 2 external drive bays and only 1 internal bay. The sub-mini and micro are targeted at the low end computer market and usually have very limited possibility for upgrade and no room for expansion.
Remember too, that there can be some pretty fine lines between the different case styles. One company's mid-tower might be another company's midi-tower. One might take out a single 5-1/4" bay, and call it a mini-tower, whereas the next manufacturer may still refer to it as a mid-tower.
Form Factors
Cases come in different sizes and styles, and so do motherboards. The size and shape of the circuit board, the position of the components, the position of the screw holes, and the technology incorporated make up a motherboard’s form factor. If you buy a new computer, it’s not really a problem because the system board is already in the case. But, if you're building a computer, or buying a new case for a computer, then you have to be sure the case will accommodate the motherboard’s form factor. The case gets its form factor name based on the form factor of the motherboard that it will accommodate.
ATX - The ATX motherboard has the different I/O connectors, serial, parallel, and USB ports hardwired directly to the motherboard in a small cluster at the back of the computer. The power switch on the ATX case is connected to the motherboard, not directly to the power supply, and there is power to the board at all times. The cases come in all the regular sizes and styles. The ATX is currently the most popular form factor out there.
There is a slightly smaller version of the ATX called the Mini ATX. Although the motherboard is slightly more compact, it uses the same case and power supply. I mention it here, only to differentiate between it, and the Micro ATX.
The more compact version of the ATX is called the Micro ATX, and it's targeted toward the low end computer market. The cases generally have about 1 X 5-1/4" bay, 1 X 3.5", and 1 internal bay. The Micro ATX power supply is also smaller, and usually has just enough power for what's already in the computer. There is very little (zero) room for expansion. I think the Micro ATX probably came about as a result of manufacturers competing for that first 'under $1000' computer.
ESD - Electrostatic Discharge
ESD is simply the discharge of built up static electricity. Electrostatic discharge however, should not be taken lightly when working with computers. ESD has the capability of causing enough damage to the components inside your computer to render it completely inoperable. It's important to use an anti-static strap and/or a grounding mat whenever working on the inside of your computer. Being aware of ESD precautions can significantly reduce the chance of damage to your computer due to static electricity.