Finally, check out the dimensions of your gear to make sure the pieces will fit in your chosen case. Aftermarket coolers and top-end graphics cards take more space than you might think, and even midrange graphics cards could have trouble squeezing into some compact cases.
Before you build
While you're pulling all of your pieces out of their boxes, be sure to keep track of the plethora of screws and cables you're yanking out with them. Building a PC involves a lot of tiny screws, and they're not always the same type of screws. Stay organized.
Most of the PC building process itself should be straightforward, especially once you read the manuals. Following the installation instructions on a multihundred-dollar investment is a must, even if you're a DIY vet and you know what you're doing. Building a PC is an intricate, methodical process, and missing a crucial step early on could mean disassembling your entire machine later.
Preparing the motherboard
Now for the fun part! It's time to roll up your sleeves, dive in, and—stop. No, seriously. Before you install your first component or do anything else, take your motherboard's I/O shield—the cover for the ports on the rear of the PC—and install it in the case now. If you forget to install the I/O shield, you'll have to pull the entire motherboard out sometime down the line to put it in its rightful place, and that's a big headache. (Trust me.)
As for the main parts, the CPU is the heart of your PC, and you'll want to install that first. The process is fairly straightforward; just make sure that both the processor and the socket you set it into are clean before you install it, and be gentle.
Once that's done, the next natural step would be to install the CPU cooler. But hold your horses! If you're using an aftermarket cooler rather than the small, stock cooler Intel or AMD provided, install your RAM first. A large cooler can make it difficult to insert RAM into the memory slots after the fact.
The most common mistake when installing RAM is simply not reading the manual. Does your motherboard favor dual-, quad-, or triple-channel memory configurations? Placing the memory sticks in the correct manufacturer-appointed slots is crucial, too: If you don't do your homework, your system could wind up using a single-channel configuration instead, which will drag down performance.
RAM in place? Okay, now it's cooler time.
Cooler installation tosses a few curveballs at you. The cooler's heat sink sits atop the CPU to draw heat away from the processor, with a thin, air-bubble-free layer of thermal paste between them. Some coolers, including stock AMD and Intel models, ship with thermal paste preapplied. In contrast, most aftermarket coolers require you to apply your own thermal paste.
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