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How to build a compact, energy-efficient PC

Put together a space-saving PC

We show you how to put together a space-saving, energy-efficient PC for home or office use - UPDATED: 23rd Feb 2012

Chances are, there are several computers in your home. Perhaps you have an old PC which has been replaced by a laptop or even a tablet PC. However, PCs still have their advantages, not least of which is a large screen and keyboard. Plus, you may want a low-powered, small machine for the whole family to share in the main living area. It's convenient when you need to respond to an email, or keep an eye on what the kids are looking at on the internet.

Such a shared PC needn't be expensive to build: it doesn't have to run games, so can rely on the motherboard's integrated graphics chip. You might have been using an old PC for this task for years (or even an old laptop), but now is the ideal time to replace it with a new PC and invest in a larger, better-quality monitor.

Defining your needs

Unless you plan to connect the PC to a corporate network, you can use Windows 7 Home Premium rather than the more robust Windows 7 Professional or Ultimate editions. If the computer is to be used in an office environment that would connect to a domain name server, you'll probably want Windows 7 Professional, which costs roughly £40 more than Home Premium.

You could argue that Linux might be a great alternative for a light-duty, shared PC. There are several distributions that are tailored towards younger users, and Qimo4kids is a good one to start with. For everyone else, Ubuntu is likely to be the best choice as it has great community support and is constantly being improved.

Here are capabilities the new system will need:

> More responsiveness than the old PC or laptop. A faster storage system, more RAM, Windows 7 and a more powerful CPU.
> Relatively low power consumption. A desktop PC with a separate display will likely consume more power a laptop, but less than an old PC with a CRT monitor. Robust sleep and hibernation are pluses, too.
> A good wireless keyboard and mouse; both should also have long battery life.
> Wi-Fi capability, either built-in or through a USB dongle since the PC could end up far from your router.

With these thoughts in mind, let's take a look at the list of components we've chosen.

Hardware

As we'll be using a motherboard with integrated graphics and a case with a built-in power supply, the parts list isn't too long. This isn't necessarily the cheapest system to build, though. Our priority was functionality. Using laptop-class components, for example, pushes the price up a bit, as does using special, low-voltage DRAM. You can save money by opting for standard RAM and a case that supports a desktop optical drive, but it won't be as small as this PC.

Intel Core i3-2100T CPU

Although we wanted to go small, we didn't want to sacrifice power and go down the Intel Atom route. Instead, we've opted for a Core i3-2100T. This CPU has a TDP (thermal design power) of just 35W, which is almost half the 65W of the regular i3-2100 processor. Despite this, its two cores run at a healthy 2.5GHz and hyperthreading makes it effectively a quad-core CPU. The only sacrifice is TurboBoost, so it doesn't automatically increase its speed when running demanding tasks.

The chip also supports hardware virtualization, which can be useful in an office environment. However, the 2100T doesn't provide Intel vPro or Trusted Execution, features that support remote management.

Motherboard and case

Intel's DH67CF is a mini-ITX board with two memory sockets and a PCI Express x16 slot that could support a graphics card, but that will go unused in this build. There are lots of ports, including a DisplayPort output, a standard that's becoming increasingly common in mid-range flatpanels.

Intel DH67CF motherboard

The motherboard's only real oddity is its CMOS battery. It's on the end of a wire, attached to the board through a pair of pins. You can see the battery just behind the DVI port block.

Since the plan is to keep power consumption and physical size down, we looked for a suitably low-power mini-ITX case with its own power supply. The Antec ISK 300-150 fits the bill nicely, with its understated black bezel and 150W PSU. Antec makes a similar chassis with a 65W PSU, which would probably have worked fine, too; but it's important to remember that the PC will draw only the power the components need – it won't consume 150W just because it has a 150W PSU.

Antek ISK 300-150 case

Antec includes a bracket that allows you to stand the machine on its side so that it takes up less desk space. If you buy a wireless keyboard and mouse set, they can easily sit on top of the case when no-one is using them.

Memory and storage

To reduce power consumption as much as possible, we've installed a pair of 2GB Kingston HyperX LoVo (low voltage) DDR3 modules. The kit costs around £10 more than standard DDR3 modules, so you can save money here if power consumption isn't your biggest concern.

Kingston HyperX LoVo memory

For storage, there's a pair of laptop-class devices. One is a Western Digital Scorpio Black 750GB, 7,200rpm hard drive. You could swap this for a 120GB solid-state drive, but that would push the cost even higher and limit the amount of space for large files such as videos. The second is a Samsung slot-loading rewritable-DVD drive. The slot-load feature is nice to have in a crowded, small-desk environment. Again, both components use less power than their desktop equivalents.

Samsung SN-T083C DVD re-writer

Building the System

As with any compact system, building into a small case can be tricky. The Antec ISK usefully accepts laptop storage, so you won't need any brackets to install the hard disk and optical drive. This illustrates a key point: make sure that your components all play well together.

It's all too easy to buy a graphics card that's too long and blocks access to SATA ports or memory sockets. Conversely, you may find the case you've chosen isn't deep enough to accept the graphics card you want to use, so if you stray from our recommendations, make sure you check your measurements. Spending a little time on research will ensure that all your components fit well. Fortunately, Antec thought of this and included a laptop-style SATA power connector that's smaller than the SATA power connection in desktop drives.

In such tight quarters, parts such as the CPU cooler can create issues, too. However, Intel's Core i3-2100T ships with one of the lowest-profile CPU coolers we've seen. It won't win any awards for cooling an overclocked CPU—but that's not what it's designed to do. Its job is to keep a 35W CPU cool enough in a small case, and it did that well enough: idling temperatures were around 40 to 45 degrees Celsius.

Final Thoughts

The total cost of this compact, power-efficient and quiet PC is a little under £500. You'll need to reuse an existing monitor, keyboard and mouse, or invest in new ones using our Top 5 charts to find the best-value examples. Naturally, you can build cheaper systems than we've demonstrated here with a few tweaks. Using a slightly larger case than the Antec ISK, for example, would allow you to use cheaper desktop storage. Similarly, you can reduce the amount of hard disk space and RAM to save a few pounds here and there.

Total cost of components: £491 inc VAT

CPU: Intel Core i3-2100T, £101 inc VAT
Case: Antec ISK 300-150, £65 inc VAT
Motherboard: Intel DH67CF, £91 inc VAT
RAM: Kingston HyperX LoVo, £37 inc VAT
DVD Drive: Samsung SN-T083C, £31 inc VAT
Hard drive: Western Digital Scorpio Black 750GB, £80 inc VAT
Operating system: Windows 7 Home Premium, £70 inc VAT
Wi-Fi adaptor, D-Link Wireless N 150 USB Adapter DWA-125, £16 inc VAT

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