computer case and power supply buying tips

HOW TO BUY A COMPUTER POWER SUPPLY


The computer power supply is the Rodney Dangerfield of all the components that make up a computer. The computer power supply just doesn't get any respect and its job is one of the most important of any component for your computer's longevity and performance.
Specifically the computer power supply's job is to convert the AC power supplied by your home into nice clean DC power for your computer.

What the Computer Power Supply Really Does
The computer power supply's main job is to supply three different DC (direct current) voltages to the computer. These voltages are as follows.
+12VDC for motors and voltage regulators, newer processors
+5VDC for motherboard, voltage regulators, serial & parallel ports, PCI & AGP ports
+3.3VDC for the motherboard chipset, system memory, PCI & AGP cards
The computer power supply also regulates current and helps to cool the computer with its intake and exhaust fans. The direct current supplied by the power supply must also be free of noise, spikes and dips in voltage (

Don't Buy a Cheap Computer Power Supply
A good computer power supply will run a series of checks before it allows the motherboard to turn on. If everything is ok it sends what is called a Power Good signal to the motherboard. Once the motherboard has received this signal it knows it is okay to boot up.
Cheap power supplies may not perform their internal checks before sending the all clear signal for the motherboard to power up. This can cause damage to the motherboard or other components in the computer because the proper voltages are not present at startup.
Hopefully this has convinced you not to trust the cheap power supply that often comes with a case.
The recommended brands for the best power supply are Thermaltake and Coolmax. Quick Guide for Computer Power Supply Wattage
Here's a quick guide to determine the total average wattage of the different components the power supply will be supplying power for. Do the math and then add a 100 watts (just to be safe) and you've got an idea (ball park) of the total wattage needed for your computer.
Motherboard-, 15-30 watts
Low-End CPU-, 20-30 watts
Mid To High-End CPU-, 40-100 watts
RAM-, 7 watts per 128 MB
PCI Add-In Card-, 5 watts
Low To Mid-Range Graphics-, 20-60 watts
High-End Graphics-, 60-100 watts
IDE Hard Drive-, 10-30 watts
Optical Drives-, 10-25 watts
ATX Connector

The computer power supply is connected to the motherboard by a big white 20 pin connector. Recently this connector was changed from a 20 pin to a 24 pin. The new designation is the ATX 2.0 connector. Make sure you know which connector (20 or 24) is on your motherboard before buying a computer power supply. Also, be aware that PCI Express videocards have a connector that is not common on older PSUs (power supply units).

Cooling
All computer power supplys require some form of onboard cooling due to the heat they generate. The best type of onboard fan to have is a 12cm(diameter). These larger fans can push more air at slower speeds which results in less noise. This is a good thing. Smaller fans must spin faster to generate the same air flow and that leads to more noise.

Detachable Cables
Older computer power supplies had a certain number of power leads that emerge from the rear of the PSU. If you could use them all great, if not you had to find somewhere to tuck them. The newer computer power supplies have modular power cables that permit you to just use the power cables that you need. This is a good thing because it reduces clutter inside the computer case, which in turn increases the cooling efficiency of the fans.

Conclusion
Don't settle for a low quality power supply. Make sure you buy a quality computer power supply that is large enough to meet the computer's power requirements and that it has the right power connectors to fit the motherboard that you have picked out.
If you are using a SATA drive or running dual video cards (Crossfire or SLI) be sure your selection has the right connectors and the wattage needed to run your configuration.


BUYING GUIDE TO COMPUTER CASES

There are lots of different computer cases out there, with plenty of different styles and some strange-looking features. This article will help you sort through the jungle of cases and find the features you really need and the ones that don't really help at all.
A good computer case is important for a high-performance PC. Why? Well, first of all, PCs generate a lot of heat, and a cheap case will not be as effective in dissipating that heat from the inside of the computer. Adequate airflow is a must for any computer, if you don't want your parts to overheat. Second, the better your case the less noise your computer will make overall. Aside from that there are other benefits, like easier upgrades, a better look, etc. that don't effect performance but are nice to have anyway. In this article I will separate my features into two categories: technical features, which affect performance, and nontechnical features, which are useful but not from a performance standpoint.
Power supplies deserve more than just a passing mention and require their own separate article.

Technical FeaturesThe following are features that help with airflow, noise, and other key performance issues that arise in computers.
120mm fans, rather than 80mm fans (or even larger, I suppose). The larger a fan, the less noise it makes when blowing out the same amount of air. Just look at your ceiling fan. It creates more airflow than any fan in your computer, but makes almost no noise. A 120mm fan in the back of your case will provide superior airflow out of the case with minimal noise.
Side air vent(s). A few years ago cases were introduced that had a vent in the side of the case, directly above the CPU. These vents provide fresh, cool air from outside directly to the CPU, which allows it to stay significantly cooler, and the CPU fan also stays significantly quieter. If you think about a case without a side vent for the CPU, air comes in through the front, past your hard drives (some of the hottest components in a computer), then through most of the hot inside of the computer before reaching the CPU. By then the air cooling the CPU is only a little cooler than the CPU itself. If you know your physics, you know that heat transfers faster when the temperature difference is the highest. The inside of your case is usually 10-15oC hotter than room temperature, so the less of your case the air has to travel through the better. Newer cases come with a vent for your graphics card as well, and the same rules apply there.
Removable back expansion slot covers, not the kind you have to break off. Once you break off a slot on the back, it'll stay broken off, even if you take out the card that was there, so if you take out a card in one of those cases there's a hole at the back of your case; this will screw up the airflow in your case. When the airflow gets more turbulent, your fans are less effective. I guess this is more of a minor issue, but holes in the back of your case are still something you want to avoid (taping them over will do just fine, though).
Rubber grommets for screws. When components vibrate they cause vibrations in the screws holding them to the case, which in turn vibrate against the case and create really annoying vibration noises. Try and find a case where you have a rubber grommet in place between the screw and the case itself, which will absorb almost all the vibrations.
This isn't really a feature, but get the smallest case that fits your requirements. Fan performance is usually measured in CFM, or cubic feet per minute. So the less air your case has inside it, the faster all of it can be pushed out of the case, replacing it with new, room-temperature air. If you get a full tower case, you'll need multiple fans to achieve an air exchange rate as high as a single fan in a mini tower. And, as we all know, more fans mean more noise. (Of course, if you need to put a lot of things in the case, you really don't have that option.)

Nontechnical FeaturesThe following have no direct impact on performance, but they're still case features nonetheless.
Obviously, try and find a case that looks nice. Most cases don't look so bad that you'd want to hide them from guests, but there are definitely some out there. A standard look is really the best, but if you must go with something that looks unique make sure it's unique in a good way.
Lighting effects from the case or its fans, if you like it. Lights illuminate the area around the case, and a lot of people like the effect. You don't really lose anything by putting lights in your case; even if your case doesn't have any lights, you can buy light sticks that plug into your power supply, so it's not a big deal either way.
Tool-less installation. In some computer cases, the only time you'd need to go get a screwdriver is if you are replacing the motherboard. Tool-less installation is always less of a hassle and usually faster than installing parts with screws (plus there aren't any screws to lose).
Dull edges inside the case. Sharp edges can easily cut you if you're not careful. Make sure all edges in the case are rolled over so there's as little a chance as possible of being cut by them.
Front USB slots, and audio/1394 ports if you need them, are very useful. It keeps you from having to find a slot at the back. They're especially useful for using a USB flash drive, updating your MP3 player's songs, etc.
A window in the side panel could be a good or bad thing. If you like seeing the inside of your case, cable clutter and all, go for it. But if it doesn't matter to you, the plastic window will cause vibration noise, and it also won't block noise as well as a steel or aluminum panel.
Things to AvoidThe following are things that will actually hurt the performance of your computer.
A side fan. It looks great on paper, right? I mean, how can having another fan not be good for your computer? Let's consider the two scenarios. If the fan is blowing air into the case from the side, it disrupts the smooth front-to-back airflow that's already there. And if it's sucking air out, it's taking air away from the CPU, which means the CPU fan has to work harder to get the same amount of air to the CPU. Neither of these is better than what you already have without a side fan. The side vent helps you to get air to the CPU, but a side fan will disrupt this airflow and result in higher noise and hotter components.
Air filters on any vents in the case. While they keep dust out of the computer, they also make it harder for air to come in and go out of the case. This either causes your fans to spin faster or your case temperature to go up, neither of which is good. You're better off opening up the case once a month and using a vacuum cleaner to clean out the dust (don't worry, it's not harmful at all as long as you don't knock anything loose - I do it all the time).