Designing and Assembling Your Own PC

© 2011 - Bruce Fowler - brf531[at]

with Leo J. Carling III - leocarling[at]

The Project

This essay describes the design, procurement and assembly of a custom-designed desktop computer. The ideas and techniques used may be of interest to others considering a similar course of action.

We recently decided to replace an old Panasonic Toughbook (a notebook computer) because it was too slow to handle current applications. We wanted to explore the DIY (Do It Yourself) route. Building a replacement notebook computer was out of the question. The physical design of notebooks is very challenging, often using non-standard parts to fit everything into the available space. We decided that the replacement could be a desktop machine. Assembling a PC from readily available standard parts then became an easy choice.

Building a computer from parts sounds like it is a complex and difficult technical project. Fear not, it is really a very straightforward undertaking. That is because widely accepted standards allow parts from different manufacturers to work together with few surprises. The surprises you do encounter can become learning experiences. This improves not only the computer but the computer's user as well!

Gone are the days when the typical PC required a separate PCI card for a network interface, audio and video outputs. Most desktop computer users will find that modern motherboards have sufficient network, audio and video capability. Those interested in advanced video games may choose to add a high-end video card.

There are only half a dozen components in the PC we assembled — case, CPU, motherboard, memory, hard disk, and CD/DVD burner. This essay will focus on the systematic process of selecting those components. We will then go step-by-step through the process of assembling them.

Some technical terms used in the following sections may require further explanation. An excellent resource for definitions of technical terms and standards is Wikipedia ( Direct Wikipedia links are provided for some technical terms where they are first used.

Click on any of the pictures to bring up a larger view.

Why DIY (Do It Yourself)

Here are some reasons for assembling your own PC. Perhaps you:

Do-it-yourself may not be the best choice if you:

Saving money is not necessarily a priority. You may come out ahead financially if that is a project goal, but buying single parts cannot compete with the purchasing power of a name-brand manufacturer. You do get the choice to make trade-offs between cost, features and quality in your selection of components.

Project Objectives

What is the problem we are trying to solve? Answering that question requires that you clearly define how you intend to use your new PC. There are many valid answers. You may need a file server, a general-purpose desktop PC, a media center, a basic machine for a child, a web/email client, or perhaps a screaming game machine with graphics that would put Hollywood to shame.

Setting a broad outline allows you to think about physical size, noise level, and other factors. You may need an HDMI interface to connecting to a TV set, or an optical drive for reading and writing DVDs. Getting all this straight early on helps keep your thoughts focused when later shopping for parts.

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The Finished Product

Our informal objectives were:

Money is always an issue. How much you are willing to spend adds a healthy constraint on the design process. However, you will need some flexibility to deal with the realities of the marketplace. We decided to see how far $400 would take us. With that constraint in mind, we started visiting vendor web sites to investigate what was available.

Later we will be specific about our final hardware configuration. That is not a secret. However, the emphasis here is on what you might want to build, so we will focus on the process.

Designing Our Custom PC

Design is the most critical stage of the project. Turning a screwdriver is the easy part. The hard part is figuring out what to assemble. While designing your "dream machine" you will quite likely spend much more time skipping from one vendor web site to another than you will actually putting it together.

Design is an iterative process where you need to make choices at increasing levels of detail until you are satisfied with the result. You may run into a dead end. If so, you need to back up to some previous step and try a different solution. You are exercising judgment and making decisions at each step. Those decisions have to be based on facts and knowledge.

There are many components and options available, simply too many to explore them all. Apply your own prejudices and experience to help narrow the range of choices. You may favor one brand of CPU or disk drive because you have had good experience with certain manufacturers. However your preferred components may not be price competitive. Then you need to research other options.

The experiences and prejudices of others are also valuable. Vendor web sites often invite customers to provide "Reviews," "Ratings," or "Customer feedback." Opinions confirmed and reenforced by several reviewews are sure to have some basis in fact. Think twice if several reviewers report, for example, "Has cheap plastic parts that break off in the first week of use."

PC magazines and on-line sites often review products. We often find these reviews to be superficial and overly positive, compared to the raw customer feedback.

Now is the time to visit vendor web sites to check on the features and price of each component.

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Review Processor Specs

Choosing a CPU

The CPU should be the first item on your shopping list. It is the heart of your computer; its requirements will drive the choice of many other components. It is the smallest component, and likely the most expensive. Choose it with care.

Vendor sites give you a lot of information about availability and price but not a lot that is useful for feature comparison. You need to go to the manufacturer's web site for the hard-core technical information. We wanted to use an Intel CPU, so we visited their site. You will find that the Intel site is a challenge to navigate, but persistence has its rewards. The site has a wealth of technical data about Intel CPUs and other Intel products.

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Find a CPU Within Budget

We found that a Core i3 dual-core processor met our needs and fit the budget. The Intel site confirmed that the only difference between the different models of Core i3 processors is the speed. We also found that the Core i3 has a built-in graphics capability that is adequate for this project.

Experience suggests that if you back off from the top speed choice in a range of processors, the price falls off faster than the performance. There is a "knee" in the price-performance curve. A processor that is 10% slower may cost 25% less. One can confidently make this kind of trade-off only after a few trips back and forth between the vendor and manufacturer sites. After a while, some of this starts to make sense. We settled on an Intel Core i3-540 for at about $124.

Product names can lead you astray. The Intel Core i7 sounds like a feature and speed upgrade from the Core i3. But, it is a quad-core chip. The extra cores squeeze out the graphics circuitry. If you choose a Core i7, you will need an add-on graphics card. That would have blown the budget on this project.

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Motherboard Must Fit Case And CPU


The CPU requires a matching socket on the motherboard; in our case an LGA1156. Our search for motherboards is therefore limited to those with that CPU socket. We also wanted a smaller than average computer, so we checked out micro-ATX boards. Many vendors sell micro-ATX boards. They are square and measure 9.61 inches (244mm) on a side. A typical one supports many features: SATA disks, HDMI video, built-in audio, plenty of USB connectors, and so forth. It is common with this kind of project to find components with features you may never use. Just be sure the features you need are there!

We selected a board by ASUS with a list price of $87. At the time of ordering, they were out of stock, so after due consideration we moved up to a more capable version at $99. Then the price of that one went up to $102 by the time we placed the actual order.

It seems that on-line vendors change their prices almost hourly. When we finally placed our order, the price of the memory had gone up by $3, but the CPU was $10 cheaper. Our suggestion would be, put parts you are considering into the vendor's shopping cart but do not check out. The parts can stay there for days. You can remove them later if another choice is better, or if the price comes down.

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Memory - Compatible and Cheap


The CPU accesses memory through chips on the motherboard. The physical packaging, speed and features of the memory modules have to be within the range supported by the motherboard. We need to consult the motherboard users manual to find which memory modules are compatible.

We downloaded the motherboard manual from the ASUS web site and found several pages of "Qualified Vendor Lists" for various memory and CPU combinations.

Our design called for four gigs of memory split between two sticks, leaving two slots on the motherboard for future growth. We scanned the Qualified Vendor Lists until we found the right size and speed, a familiar manufacturer's name, and a good price. The approved chips are not the only ones that would have worked, but we stopped looking when we found a name brand that fit our design for $44.

If you have memory lying around that seems to match, it won't hurt to try it. You might be fortunate and save some money.


The selection of an ideal case is critical, both from a practical and aesthetic point of view. The case has to hold all the parts we want to put in it, and it should look good, too. The variations are mind-boggling. In addition to desktop use, there are cases for rack mounting, ones to put in your car, ones for media center use, industrial cases; some even can be mounted on the back of your monitor. This range of support for the micro-ATX form factor suggests we made a good motherboard choice.

Selecting the best case takes time. We spent more time looking at cases than at any of the other components. Unfortunately, there is a lack of detailed description on vendor sites. We looked at the pictures and tried to figure out if the case would look good and be serviceable. Then we went to the manufacturer's site for the detailed specifications.

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The Case is What We See

We finally found a mini-tower case that stands vertically. It looked good and would hold all that we wanted to put in it. It is 11" tall by 4" wide by 15" deep; that fits the "small computer" description.

The power supply usually comes with the case, so compatibility with the motherboard must be assured. A little extra power capacity is good, It then is able to support future expansion of your system. That also means that the power supply will not operate at full capacity, which should extend its lifetime. The case we selected has a 450 watt power supply with its own cooling fan. The fan makes more noise than we would like. In all other respects, the case we chose is more than satisfactory. Its construction is solid, and has an overall pleasing appearance.

Hard Drive

Any modern SATA drive will do just fine. You could opt for a slower speed drive if you want it quiet, or go for a SSD (no moving parts) drive for no noise at all. Hard disks are so big and so inexpensive that almost any drive will do. They all have the mounting screw holes in the same places.

When "Seagate" and "$40" appeared on the same line with the word "SALE," we quickly hit the "add to shopping cart" button. We thought it was a 320 gig drive. On delivery it proved to be 500 gigs.

Your first choice for the computer interface is SATA. Only go with PATA or IDE (same thing) if that is all your motherboard supports. A simple adapter permits connection of old-style IDE power "Molex" connectors to the smaller SATA power connectors.

You should consider other hard drive configurations. For example, RAID 1 disks provide instant backup by writing all of your data to two drives that "mirror" each other. Thus, if one drive fails, your data is still safe. RAID is not part of this project, but we have used it in the past and it is slick.

One nice thing about having assembled your own machine is having the confidence to replace failed parts, a hard drive for example. Or, you might elect to swap out that hard drive for an SSD when they become more affordable. It's all part of the fun.

CD/DVD Drive

You may shop by brand name and/or price and be well covered. Some say that the internal parts for all optical drives come from the same factory. Our theory is that the more alphabet soup in the description of the drive the better it must be.

It is possible to get a perfectly good drive that will write DVDs for about $25, it makes no sense to settle for less than that functionality. You should consider a blu-ray optical if you are building a media center computer. Blu-ray is becoming increasingly popular for high definition video recordings.

LightScribe is another feature you should consider. It uses the recorder to paint text and artwork on the back of the DVD, as a label. While not part of our project design, the burner we used included light-scribe as an unplanned bonus.

Lastly, some top-of-the-line DVD recorders use Dual layer DVDs. They can store approximately 8.5 gigabytes of information. This is an option to consider if you need that much removable storage.

Time to Put It All Together

Now let's set up for the assembly. First a few common sense precautions:

You will always need additional parts, or end up with extra parts, in a project like this. It is good to have a "spare parts" box for that occasional missing cable or screw. Two examples of that last point:

We bought a couple of 12" SATA cables on a whim because the shorter length seemed a better fit for the small case. The two SATA cables supplied with the motherboard have a right angle bend on one end. Connecting to the "wall mounted" hard drive with those cables is not possible. Using the right angle on the motherboard end would cover up the number two SATA header. We finally used one of the supplied cables, and one of the 12" cables we purchased. The other two cables are now in the spare parts box for the next project.

The OEM drives we purchased did not come with mounting screws. We easily fixed that by "scrounging" from a retired computer.

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Fedex and UPS - Santa in Disguise

Setting Up for the Build

There is a period of waiting and anticipation once that final "Submit Order" button is clicked. In our case there were only two cartons and one smaller envelope (12" SATA cables). All showed up in less than a week.

This picture also shows the small temporary worktable we set up. We folded an old tablecloth on top for cushioning. It made a great work surface. There are also two floor lamps, one at each end of the table, to give plenty of light.

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Collect Tools You May Need

Collect in advance all the tools you think you might use to assemble your computer. The same goes for any stray parts you anticipate needing.

A #2 Phillips screwdriver will be your most frequently used tool. Needle-nosed pliers may help you fit tiny wire connectors together. The muffin tin (see photo) was borrowed from the kitchen on short-term loan. It helps keep stray screws and other small parts separated, and from finding their way into the carpet. You can put little notes in the cup with the small parts as a reminder of where to reinstall them. The blue package is thermal grease for the heat sink-to-processor interface.

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Not All That Many Parts

We printed a few selected pages from the motherboard manufacturer's user guide. They appear in the lower left corner of the photo. The document had been downloaded as a ".pdf" file during the project's design phase. The hard copy packed with the board was much more difficult to read.

The basic parts are hard drive, processor, DVD burner, memory, case, and motherboard. The only complicated task is mating the motherboard with the case. We will walk you through the assemble process step by step.

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Bracket Mounts CD Drive

The Case

The computer case is the part you would most like to see and touch before buying. Regrettably, it is the most variable and least documented. You must trust that those who designed it were knowledgeable and creative.

The case we purchased is "as advertised." It has space for the motherboard and disk drives, but none to spare. There is a spring-loaded door covering the CD drive. Another door covers two USB front-panel connectors, audio connectors and a memory card slot. There is even a reset switch conveniently located on the front panel. The case is well constructed. It neatly received all the components we needed to install. We hope you will be as happy with your choice as we are with ours.

The hard drive mounts on a metal bracket that is then attached by screws to the side of the case. The bracket accommodates either 2-1/2 or 3-1/2 inch hard drives. The CD drive mounts in its own bracket that, when screwed into the case, lines the drive up with the access door in the front panel. It was imperative that we connect the power and signal cables to the hard drive before installing the CD drive. Otherwise, access to the hard drive would be impossible.

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Make Sure Power Works

The only way to test most of the components we purchased is by assembling them and firing up the computer. One exception is the power supply. We had a power supply tester available, so we hooked it up to the bare power supply for a quick check that all the voltages were present. Actually measuring the voltage levels with a voltmeter is recommended. That could prevent frying some expensive chips if the power supply is not wired correctly.

Mounting the Motherboard

The motherboard barely fit into our case. We loosened the power supply and slid it out of the way to permit the motherboard to slide into position. The picture shows a "trial" fitting. The motherboard ports are sticking out through the large hole in the back of the case.

Different motherboard port configurations need to be accommodated by the case design. The way this compatibility problem is handled is quite simple. There is a large hole in the back of the case of a standard size. The motherboard manufacturer supplies an "I/O shield," a thin sheet of spring steel, that fits into that hole and has smaller holes that match up with the ports on the rear of the motherboard.

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Matching the Ports to the Case

Getting the I/O shield in place can be a bit tricky. It snaps into the case from the inside. A series of metal fingers and tabs must fit around the motherboard ports as the board is guided into place. Easy does it. When the motherboard is in place, see that the motherboard mounting holes match up with the mounting standoffs in the case.

You may find that some of the holes or standoffs are not used for your motherboard. Cases are designed to be adaptable to several sized of motherboard. Remove any unused standoffs else they may short out circuitry on the bottom of the motherboard. Then fasten the motherboard in place using the mounting screws.

One is tempted to install the memory and processor on the motherboard before mounting the motherboard in the case. That is not a good idea. The mounting pins for the CPU heat sink normally extend through the motherboard and out the other side. If the board is against a flat surface, the heat sink pins will not have room to snap into place. Mounting the motherboard in the case first is the best practice.

CPU and Memory

Installing the CPU is the nearest thing to a clean room operation you will need to perform. A speck of dirt on one of those hundreds of tiny contacts would disrupt the operation of the entire computer. It is definitely a time to be nervous.

Before opening the CPU package, align the processor so that it is properly positioned relative to the socket. Tiny markings on the processor and socket show the correct orientation. Check the documentation if in doubt. Handling the CPU by the edges, drop it into place and see that it fits down properly in the socket. Then close things up quickly before any dirt can get in there.

Optimum heat sink performance requires full contact with the processor. Most processors now come with a strip of thermal material attached. Adding a small dollop of thermal grease is O.K., just not so much that it oozes out the sides when the processor is clamped down. When in doubt, follow the manufacturer's instructions.

There are four possible orientations for the heat sink. Use the one that gives the best airflow and neatest wiring layout. If your heat sink has flat blades that are all oriented in one direction, line them up with the airflow within the case. See if that makes for the neatest run of wire from the CPU fan to the correct fan connector on the motherboard. Remember, one of the fan connectors is for the CPU heat sink fan, others are for case fans. Check the documentation.

Installing memory is mostly a matter of getting it right-end-to. The memory cards fit over bumps in the socket that key them into place. Plug pairs of memory cards into sockets of the same color. Visually lining the card up and sliding it into the slots at the ends of the socket is not too hard. However, quite a bit of pressure may be needed to snap the memory card fully into place. When it is properly inserted, small levers at the ends of the socket will close around it. Ground yourself often when handling memory, the chips are very sensitive to static discharge.

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Motherboard Mounted in Place

You will always encounter some surprises when building a custom computer. Recall that we purchased an upgraded motherboard. It has an IDE (PATA) port that allows use of a CD reader or an older-style hard drive. The port is located on a corner of the motherboard, to the left of the power supply wiring in this photo.

The motherboard manufacturer used a connector that is parallel to the face of the motherboard. It is "aimed" at the back of the power supply. Surprise! There is no way to plug a cable into that socket, making it impossible to use IDE storage. This does not matter to us, since we elected to use 100% SATA. It just shows what can go wrong when assembling custom components.

Hard Drive and DVD Drive

Both drives mount on sheet metal trays, or caddies, that slip into the case. The case comes with screws to mount the caddies. However there were no screws to mount the drives! Fortunately, they are easy to find. We salvaged some from a discarded computer.

It would be nice if all of the mounting screws were the same size. They are not! Short 6x32 screws fasten almost everything in the case. For some reason lost in history, CD and DVD drives use smaller and finer threaded screws. A good phrase to remember is, "bigger drive, smaller screws."

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Sort Them by Function

Hooking It All Up

The jumble of wires in the case is a challenge. Sorting and grouping them by function can help get things organized and reduce your angst. Note that the fittings on the ends of wires are called "connectors" or "plugs." The places they connect to on the motherboard are called "headers" or "sockets."

Wires from the front panel switches, lights and ports are the finer ones terminated in miniature jumper-sized connectors. Cryptic notations on the connectors name the purpose of each wire. Pay attention to the color of the wires because color gives information about pairings and polarity.

The large-gauge wires from the power supply are not individually labeled. Fortunately, they terminate in standard plugs that fit only one socket. Spare power plugs for additional disk drives are usually furnished. Leaving them unconnected will not cause problems.

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Diagram Shows Wire Connections

The motherboard manual is your friend in figuring out where each of the wires should be connected. The manual has a diagram showing all the sockets and headers and the function of their individual pins. We printed an enlarged, easy-to-read version of that page from our ".pdf" copy of the manual. Work carefully, hook wires to their headers one at a time, and all will be well.

The motherboard we used supports six USB and six SATA connections. We used three USB headers for the front panel connections, two for USB ports and one for the flash-card reader. Two SATA headers hook up to the hard disk drive and DVD drive. Each of the headers is individually identified. The SATA headers, for example, are numbered from SATA1 through SATA6.

Experience suggests that it is better to use the headers in order, low to high, and not just plug into the nearest one. Some BIOS have trouble identifying which is the boot drive if drives are hooked up out of order. Bottom line: Put your hard drive on SATA1 and the DVD on SATA2. We used the USB headers from low to high also, although the USB order is not as critical.

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All Hooked Up

You will have a hot and unhappy computer if you overlook hooking up the case and CPU fans. Some fans have three pin connectors and others have four pins. The motherboard headers can also be three pin or four pin. The fourth pin is for speed control and is usually only used on the CPU fan. You can connect three pin fans to four pin headers and vice versa, the fan will spin in either case.

You may need to try routing the wires several times before getting an acceptable result. The object is to create a workman-like arrangement of the wires without over-stressing them or blocking the flow of cooling air. In some instances, routing front panel wires under the motherboard before bolting it into place will be the best solution to the puzzle. Neat wiring is worth the time and effort in any project. It is especially important when working with a small case. Here is how our project appeared with everything plugged in.

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Cable Ties Applied

Check out the snazzy heat sink below the processor. The ASUS motherboard manual states, "... the beautiful shape upgrades the visual enjoyment for motherboard users," and, "The ASUS crystal-shaped heat sink will give users an extremely silent and cooling experience with the elegant appearance!" Who could ask for more? It is nice to see aesthetic considerations applied in the design of piece of consumer-grade electronic equipment.

The wiring looks a lot better after the application of a couple of wire ties at judicious locations. We might have obtained a neater result by dressing each of the wires into place as we routed then to their destinations. Important goals are to keep the wires out of the fans, and to avoid blocking the flow of cooling air.

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Always Review Bios Settings

Testing and Software Installation

After one last visual check, it is time for the smoke test! We do not recommend jumping in with both feet. Be more deliberate. Take things one step at a time.

First, locate and connect a display, keyboard, and mouse. A connection to the internet is not needed at this time. Next, boot into the BIOS setup screen. The motherboard manual will tell you which key to press to make that happen. All those parts are talking to each other if you get this far. Set the time and date, review the boot-up time outs, and generally familiarize yourself with other BIOS options.

We choose to change the order of the boot devices to enable booting from USB, then from the DVD drive and last from the hard drive. That setup incurs only a small cost in boot-up time. The advantage is that whenever you need to boot from a USB stick or a CD, you can just plug the stick into a port or put the disk into the drive and go.

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First Run - Memory Test

A few bad bits in the memory can cause very strange behavior in the future. Determining the cause of that strange behavior can be very difficult, because it will not show consistent symptoms.

Memtest86 is a great program for assuring the stability of your memory chips. We let it run through two complete test cycles. That took about half an hour. You are not likely to have any future trouble with your memory if it gets a clean bill of health after such a thorough workout.

Be sure to download the most recent version of Memtest86 because the program gets upgraded regularly to work with the latest memory architectures. The latest version as of this writing is 4.x. If you look closely at the picture you will note that the version of Memtest being run is 2.something, two full versions out of date. We first naively tried this antique because it was on the live CD of a current, popular Linux distribution. It does not work properly with four gigs of memory. Next time we will follow our own advice about using current software!

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Try a "Live CD" Linux OS

Moving On to a Real Operating System

Next we ran Mint, a version of Linux, from a USB stick. Using the USB stick we were able to test the CPU and motherboard without touching either the hard drive or the DVD. Adding components in steps makes it much easier to isolate and diagnose problems. Success gave us the confidence to install Windows 7.

After installing Windows on part of the hard disk, we installed Linux on another partition. We can choose which system to run when booting up the computer. This provides access to some open source applications that are not available on Windows. Pictured is the dual-boot screen.

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Finally, Loaded Windows 7

We have a legal copy of Windows 7 that we had purchased for the Panasonic Toughbook. Since the Toughbook was being scrapped, it seemed only right to transfer that license and software to the new computer. Fortunately, we had the documentation needed to prove possession of the Windows 7 license. Installation and activation took less than an hour but did require a call to Microsoft support to make it legal.

The picture shows Windows 7 working just fine on our new hardware. The only things remaining were to install user applications, and then migrate user data from the old computer to the new one.

Providing Feedback

You may choose to share the knowledge you have gained from building your own computer with other computer builders. One easy way to do that is to add your experiences to the product reviews you consulted earlier. Return to the vendor sites and add your opinion to the other customer reviews. People will be grateful if your review saves them from a bad choice, or guides them to a good choice.

Specific Components for This Project

Listed below are the major components we used for this project. This is not an advertisement or endorsement of these particular products. However, we are happy with our choices and with how the overall project turned out. Your needs and choices can and should be different.

Our total out-of-pocket cost for this project was $380, including shipping. That is $20 under budget. The less expensive version of the motherboard, had it been in stock, would have saved another $15. Pinching pennies is counterproductive, but the more carefully you shop, the more you will save.

The Next Project

The satisfactory conclusion of this project has caused us to think about what type of computer we might build next. No, it's not a zillion-core water-cooled behemoth that sounds like a helicopter landing next to the desk; quite the opposite. Here is an outline of our current thinking on this subject.

General Requirements

Present Direction

We intend to keep an eye on the "Cedar Trail" processor as it moves toward general availability. We will see who comes out first with a Mini-ITX motherboard to support it. Meanwhile we will shop for cases and watch the price of SSD drives continue to plummet. The proposed budget is $250. We plan to run Linux for the OS and use a display we already own. Spare parts do come in handy!

Watch this space to read the story of that project as it evolves.