Your Computerís Case
Your computer's case plays a large part in the overall expandability, protection, cooling and lifetime of your system.
Devices like floppy drives and CD-ROMs 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.
Hands in There
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, Iíve 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.
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 itís a panel or cover that rattles, a desk drawer being closed, or a printer that doesnít 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.
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.
Itís important not to interrupt this flow. Donít 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.
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.
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.
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.
The PC/XT was the original form factor introduced by IBM. It only came in desktop form and, though it looked pretty high-tech and streamlined at the time, was fairly large and clunky. They're not made anymore, they were replaced by the AT form factor.
Because technology had advanced somewhat, components were becoming smaller (the evolution continues to this day). Components on the AT motherboard were positioned a little more efficiently, and the size of the power supply was reduced without any loss in performance. The position of the power supply also changed with the introduction of the tower-style case. Now you could get two different styles of case, the desktop and the tower, with some variation in sizes, as well.
Cooling became much more efficient, with the power supply fan blowing air out the top, and the vent holes near the bottom of the case allowing cooler air to be sucked in. The AT form factor also moved the power switch from the back, or side, to the front of the case (remote power switch). The AT is also not available anymore.
With components becoming increasingly smaller, voltages changing, and chip and component placement becoming more efficient, manufacturers discovered they could make the board smaller. They decreased the width of the AT form factor and introduced the Baby AT. The fact that less material was required to manufacture it, and the introduction of IDE connectors, and other I/O connectors that are integrated directly on to the motherboard, resulted in cheaper production costs. This made the new form factor quite popular with the manufacturer.
The case that conformed to the Baby AT form factor could now become slightly smaller in stature. That made the Baby AT form factor quite popular with the consumer.
Most of the computers above the Pentium MMX have gone away from the Baby AT format, to the ATX. But as long as the Pentiums 200 - 266 remain a useful and plentiful machine, the Baby AT form factor will probably remain available.
The component configuration on the ATX motherboard is fairly similar to the Baby AT. By taking the Baby AT and turning it 90 degrees, the CPU and memory modules become more easily accessible. The Baby AT introduced integrated I/O connectors that attached, via small ribbon cables, to the ports installed on slot-plates at the back of the computer. With The ATX, integration is taken one step further. The different serial, parallel, and USB ports are hardwired directly to the motherboard in a small cluster at the back of the computer.
The power supply connector has changed a bit also. P8 and P9 connectors have been replaced by a single tabbed connector. The remote switch on the ATX 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.
There is another case and MB combination, the NLX, which may become more popular than the ATX. Mostly due to the fact that the big name manufacturers use the NLX form factor extensively to mass produce systems at a reduced cost. The NLX has a single expansion slot on the motherboard. There's a riser card that fits into the slot and contains the rest of the expansion slots required by the system. The whole idea is to be able to make the case narrower, and it does the job. The case is no longer limited by the height of the expansion cards because the expansion cards are installed horizontally. Although NLX is a recognized standard, and the parts are supposed to be interchangeable, they still seem to be quite proprietary. You'll recognize the NLX by the horizontal slot holes at the back of your computer.