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How Build a Desktop Computer System from Scratch

This tech-recipe explains the basics of building a computer system and includes essential topics such as planning a system and understanding compatibility. This guide will allow any user to get started constructing a desktop, regardless his or her level of experience.


Building a computer from scratch is one of the first steps to advancing one’s technical skill and prowess. It is also a skill that will save you money since you will probably no longer need extended support or someone or some business to fix your pc, etc.

One of the main points to remember about a computer is that it is just a number of systems that work together. It is similar to how the separate systems of the human body work together. Another aspect to keep in mind is compatibility. Compatibility is very important when building a computer since processors use specific pin layouts depending on their model and make. Motherboards also need to support the processor pin layout/socket size, and at the same time, they need to be compatible with your video card and memory and hard drives/optical drives. Before we go any further, let us go over the basic components to any desktop computer system.

  • Monitor/Display
  • Peripherals (i.e., keyboard, mouse, TV tuner)
  • Motherboard
  • Processor/CPU
  • Video Card
  • Memory/RAM
  • Hard drive(s)
  • Power Supply
  • Case
  • Fans to cool the internals of the case

Basically, there are about eight main components to a computer. The motherboard (also referred to as mainboard) is the foundation for the system since all of the other components will connect to it (processor, memory, video card, hard drives, power supply and case fans). We need to be sure that the parts of the system we build are compatible with each other. We have to be sure that the processor socket size is supported on the motherboard, that the video card fits into motherboard and uses proper the pci-e standard, that the memory is a supported size and type, and that the hard drive supports the connector type that motherboard has on-board.

Initially, there is a lot to consider, but we can make it easier by focusing on what we want to achieve with our system and the specs we want for the price. To make things easier, I will use my latest system upgrade as an example.

My target/goal was to increase my multi-tasking performance and video conversion times. I decided that I would go with a 6-core processor and focused on that as the key component. I then found a motherboard that supported the socket size and 6-core factor, and I made sure that the motherboard supported my current hard drives (SATA3Gbs) and video card (pci-e x16). The processor to which you upgrade will determine if you also need to upgrade your memory. On minor upgrades, you can usually re-use your previous memory and save money, for example.

Motherboards – All your base are belong to us

Your motherboard is a very important part of your system. Therefore, spending extra money for a high-end motherboard is recommended. Again, this will depend on your situation (budget versus gaming or office/business use).  The motherboard (mainboard/systemboard) will dictate what kind of processor you will need to use, memory type, hard drive connection type, and other onboard features [i.e., built-in Ethernet, USB 2.0/3.0, Firewire, Video (vga/dvi/hdmi), and sound].

There are four main form factors/sizes of motherboards.

  • ATX
  • Micro-ATX
  • Flex-ATX
  • Mini-ITX

ATX is the standard form factor for normal-sized desktop computers. Micro-ATX is used in smaller form factor cases but will fit in an ATX case. Flex-ATX and Mini-ITX are super small form factors and need a specific computer case for them. (ATX will not work unless its stated for flex-atx or mini-itx.) These last two form factors are used more by modders and enthusiasts for carpc or htpc projects. Your best bet is to go with ATX or Micro-ATX since they are the defacto standards these days and cases are cheap and easy to find.

Next, we need to determine the socket size the motherboard can support.  AMD and Intel processors need motherboards that are made for the pin layout/socket size of the processor you want to use.  AMD uses AM2, AM2+ and AM3 as their processor socket sizes. Intel uses LGA 1156, LGA 775, etc. (Intel uses more variations of socket sizes than AMD.) Additionally, if your running a super high-end multi-core processor (4+ cores), you will need to make sure your motherboard supports the processor and its power use (e.g., 140w cpus, amd 6cores).

Next, make sure that the memory fits and is the proper type (DDR2 vs DDR3). Also, make sure the video card is the correct type.  

Chipsets are another essential component of the motherboard. Chipsets are computer chips built onto the motherboard that allow the operating system to interact with the hardware.  A good chipset can make a mediocre motherboard great, while a poorly performing one can make a great motherboard horrible.   Researching the basic advantages and disadvantages of different chipsets can help with performance and compatibility.

Some key points to remember about the motherboard:

  • All components need to be compatible with the motherboard you choose.
  • Choosing a motherboard and processor first will make system building easier.
  • ATX or Micro-ATX are the most common form factors and makes finding a case simple.

Processor (CPU) – The Brains

A computer processor is really the brains of the whole system. The processor executes the commands issued to it and writes its results onto the display and hard drive.  Basically, the processor functions similarly to the human brain. The brain hands out commands to the smaller subset of systems (e.g, our muscles, nervous system, etc.) that are guided by a set of instructions (i.e., programs).

These days you have tons of choices varying from more budget-friendly dual cores to the higher-end quad, 6 and even 8-core CPUs.  Again, the socket size of the processor must match up with the socket size of the motherboard.

I personally run a 6-core AMD Phenom II X6 that is clocked at 2.80 GHz per core.  For me, it takes about 20 minutes to convert a DVD9 movie from VOB to MP4 via Handbrake.  With my older CPU (dual core AMD Athlon 64 X2 clocked at 3.0GHz per core), this task would take about one hour and 20 minutes for a two hour movie.  I recommend reading reviews on places like Toms Hardware or CNET.

In the end, CPU choices are typically limited by price. Faster is more expensive.

Memory (RAM) –

Again, we will need to be sure that the memory is the proper size (DDR2 vs DDR3) and frequency (i.e., DDR3 1600/1333/1066).  Memory is fairly inexpensive these days, even DDR3 sticks.  I would recommend 4GB at the minimum.  Another thing to remember when choosing memory and amounts is that, in order to utilize 4GBs of memory or more, you will need to run a 64-bit version of Windows or Linux.  Keep in mind that 32-Bit Windows is limited to recognizing only 3GB of physical memory, so if you have 8GB of memory in your system, you will only see 3GB (Win7 32-bit may show up to 4GB but nothing more).

One should buy the memory of the same brand so that it matches. Use them in pairs to utilize the Dual Channel benefits of DDR2/DDR3 memory.

Memory is used by the computer to temporarily hold information while commands are being executed.  The larger the memory, the faster it can process data.  If your system runs out of memory, it will then use a page file which is typically slower than ram.

Graphics Cards (GPU)-

This component can be optional if you buy a motherboard with built-in video.  However, onboard video compared to a dedicated PCI-e video card will be a great deal slower.  Most onboard video cards will let you do most office related type work and movie playback, but it likely will not allow you to play any of the newer games. If you are gaming and want to play the latest games at maximum resolution, expect to spend over $150 for a video card.  If you are just a movie watcher, a mid-range $75-$150 card will suffice.

There is one main format for desktop video cards: PCI-e, which is also called PCI Express.  Be sure that when you buy a motherboard that it has at least one PCI-e x16 slot.   This ensures you can use nearly any new video card from a budget to a SLI ready card.  I will not elaborate on SLI since that is a whole different topic altogether (It deals with dual video cards which requires a rather powerful machine and additional experience and knowledge).

Power Supply-

After building as many desktop pc’s as I have, I highly recommend buying a modular power supply.   Modular refers to the way the cables connect to the power supply.  Most normal power supplies come with all the cables already connected to the power supply and you have a ton of extra cables you never use. With a modular power supply, you connect the cables you need to use and leave the ones you do not use disconnected. This can help keep cable management under control.

These days I would recommend a 700 watt to 850 watt power supply.  This should ensure you hae enough power to grow.  Also, stick with the name brand or semi-name brand power supplies. If you see a 1000 watt power supply on sale for $50, you probably are not really getting a 1000 watt power supply but an overrated one.  This is your computers heart!


Get a case that can fit all of your components and your motherboard’s form factor type.  Front USB connectors are very nice and convenient.  Aluminum cases are much lighter than steel ones and are worth the extra cost if you move your pc around a lot or work on it.

Most newer cases have built in screwless drive bays making removing and upgrading drives and your system a lot easier.

Putting it all together-

The last few steps are really the easiest parts.  Here is my recommended order of installation of computer components into a new case.

1. Put the motherboard backpanel i/o into your case.

2. Mount the power supply and connect to the motherboard with the appropriate cables.

3. Mount the motherboard and connect the DVD/CD/Bluray and hard drive connectors.

4. Install the CD/DVD/Blueray drives. (Install these before the CPU as the heatsink can block your path.)

5. Install CPU/heatsink and add memory.

6. Install hard drives and connect.

7. Install the video card. (You probably will need to connect a power cable, too.)

8. Connect the front panel connectors. (for power switch, reset, hdd indicator, front usb, etc.)

9.  Connect the keyboard, mouse and monitor. Power it on!

10. Hopefully, you get the BIOS POST screens.  Now, all that is left is to install an OS.

Hopefully, this will give you a good overview on what you need to consider and what is needed to build a desktop pc.


If you have problems with your system not booting, always start with the bare minimum components.  This would be the most basic items needed to power up: motherboard and powersupply connected, CPU installed, memory installed, monitor connected and keyboard hooked up.  Keep connecting things one at a time and testing booting up to figure out which component may be the problem.

Most memory or graphic card related errors will cause your system to not boot and beep a series of tones. These are diagnostic tones and googling the pattern can be helpful in debugging.

Most motherboards do not ship with the latest firmware. Once the system is up and running, updating your motherboard’s firmware is a priority.

Jimmy S
Jimmy S
Jimmy Selix is an early adopter that loves to be one of the first on the block to have the latest and greatest in technology and gadgets. Another love of his is being able to share his knowledge to others seeking it. Feel free to drop any comments or questions that you may have.


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