David Hurst

Over the years I have built numerous computers and it is now a regular occurence for people to ask me to impart some wisdom on choosing or building a new PC. It makes sense that this information may be of use to others too, as the computer industry is something of a minefield and the sort of information you commonly hear being issued in places such as PC World is often utter rubbish. So here you go: my handy guide to buying or building a fast PC.

The first thing I say to anyone asking me for advice is: “buy a Mac”. This is especially true now as all new Apple Macs will run Microsoft Windows. Why anyone would want to use Windows after using the far superior OS X is beyond me. Unless you have a specific reason for running Windows, a Mac does it better, faster and easier. If you want a recommendation on a Mac, the iMac range represents excellent value for money.

Given that you’re still reading, it’s a safe assumption you want a PC. I guess your first choice is whether to go for an off-the-shelf machine from PC World, Dell or similar, or whether you want to build one yourself. If you are new to computers, building one really won’t be an option. Whilst it is relatively straight forward to bolt parts together, installing operating systems and trouble shooting is not a topic I can cover here. You need to be computer literate and handy with tools such as Google if you want to take the DIY route. Some of the information here is a little too in-depth for buying a PC, and is more directed at system builders, but hopefully you will find enough useful information.

Step 1: Choose your processor (CPU)

Not as simple as it sounds. Let me break it down: you have a choice between Intel processors or AMD processors. Intel are a bigger and more well established company, but AMD have proven their ability and up until very recently AMD processors outperformed Intel consistently. So, either company is a good choice. Both companies do make cut-down CPUs, which I would recommend avoiding: these are the AMD Duron, AMD Turion, and the Intel Celeron. Instead, opt for the AMD Athlon 64 or better, or the Pentium 4 or better.

In the old days manufacturers used to specify the speed of the CPU in MHz, and now in GHz. You would be forgiven for thinking that this an ideal way to compare processors. It is not. Most CPUs now have model numbers, although you can usually find out the clock speed or GHz figure. Clock speed is a measure of processor clock cycles per second - the higher the GHz, the faster the processor. But, here’s the key: manufacturers do not tell you the most important figure which is IPC (Instructions Per Cycle). For example, a 1Ghz chip with an IPC rating of 3, will be faster than a 2GHz chip with an IPC rating of 1. Get the idea? Clock speed is therefore fairly useless as a comparison tool, although this is usually all that is relied upon by staff in PC World when giving advice to customers.

There is another factor which also considerably alters CPU performance: cache RAM. This is memory that the processor uses to cache instructions and thus speed up operations. The cache RAM runs at speeds far in excess of your system RAM, and is very expensive due to its tiny physical size. The cache is normally split into 3 levels, Level 1 being the fastest and the most expensive. Often, Level 1 cache is only 16KB in size. As a purchaser you will normally be interested in the amount of Level 2 cache, which on modern processors will range from 256KB up to 2MB - more is better.

Let me further explain by giving you a comparison. I have an Apple Mac with a G4 (IBM PowerPC) processor that has a clock speed of 1GHz - low by today’s standards. I also have a computer with a Pentium 4 3GHz processor, and yet the speed difference between them for everyday tasks is negligible. Obviously, this isn’t the best comparison as the Mac runs OS X and the PC runs Windows XP - they are completely different, but it does show that clock speed is really not critical. In this case the G4 benefits from a 1MB Level 3 cache, as well as having a 256KB level 2 cache, whereas the P4 has just a 512KB Level 2 cache. It may well have a better IPC rating too, but clearly cache matters.

So, with me so far?

AMD or Intel. Lots of cache.

OK, now things get more complex. Firstly, PCs are changing from 32bit to 64bit. The next version of Windows does support both, but any future version will be only 64bit. Again, it’s worth pointing at that Apple has been offering 64bit for years. Make sure the processor you buy is 64bit. In the case of AMD, all decent CPUs are now 64bit. Most top-end Intel chips have something called EM64T, which basically means they are 64bit.

A little bit of history is appropriate here. Both Intel and AMD produced competing specifications for 64bit processors, and Microsoft chose to adopt AMD’s specification. Therefore, EM64T is the AMD specification and is Microsoft compatible. Earlier Intel Xeon 64bit CPUs (most commonly found in high-end UNIX workstations and servers) are not compatible with Windows XP 64 or Windows Vista 64.

The field now becomes even more muddied, as processors are now being built with dual cores. This essentially means that you have two processors in the space of one. This does not mean the CPU is twice as quick. Speed gains vary, and whilst dual core processors are faster, they are only faster if the software using them is designed to take advantage of both cores. Most common software packages will not use both cores. Still, it’s probably worth going for dual core chips as they have a longer future.

So, you’ve decided on a brand, you’ve chosen 64bit, and you’ve decided on dual core. Now, you need to balance cost against performance, and by performance I mean clock speed and cache. Find the happy medium. For example, at the time of writing a Pentium D820+ (dual core, 64bit, 2.8GHz x 2, 1MB L2 cache x 2) is priced at £109 whereas a Pentium D840+ (dual core, 64bit, 3.2GHz x 2, 1MB L2 cache x 2) costs £370. The only difference between the two is clock speed, and the average user is never going to notice much of a difference, therefore it doesn’t warrant spending more than 3 times as much for the slightly faster chip.

Step 2: Choose your motherboard

If you are buying an off-the-shelf PC, you will be offered little or no choice on this front. Just bear in mind that this is the component that is most commonly skimped on, and yet it is arguably the most important. Don’t buy cheap.

When building your own PC, make sure you choose a good quality board. Avoid the cheap brands, unless you particularly enjoy watching your computer crash. Expect to pay £60 or more for a good board, and make sure it supports all the other components you have bought - do research on the manufacturer’s website and double check everything as this will save you much pain later.

I would recommend making sure the board offers dual-channel RAM and SATA RAID. Don’t go for boards with on-board graphics cards.

Step 3: Choose a case

Again, if you’re buying a complete PC, you won’t normally get a choice of case, but you should choose something you can live with in terms of size and appearance.

If you are building your own, make sure the case has enough space for all the components you need to fit in it. Again, don’t buy cheap, and don’t buy a case with a power supply included as it almost always will be cheap and nasty. Good quality cases have better airflow, don’t cut your fingers to pieces when building, and vastly speed up the whole build process and any future upgrades. Expect to pay £50+ for a good case. Budget for it - it is worth it.

One of the simplest mistakes you can make is to buy a case to small for the motherboard - make sure you check these things.

Modern computers need efficient cooling, so make sure you buy a case that offers good airflow and cooling design. If installing your own fans, you need at least two: one at the front to draw cool air into the case, and one at the back by the CPU to exhaust the hot air. Pay careful attention to the direction arrows on the fans: install them both inwards and you will have a case full of dust in no time; install them both outwards and they will do nothing, or; if you install them with the air flowing back to front, then you will blow dust into the CPU fan.

Whilst we’re talking about cooling, buy some cable ties and make all the cables tidy. Loose cables obstruct airflow and make the whole thing hotter. For those that don’t know, computers run faster the cooler they are.

Step 4: RAM

Frankly, these days you need at least 512MB, and you should have 1Gb ideally. If your motherboard is set up for dual channel RAM, buy a matched pair of RAM modules (DIMMs). In a dual channel configuration, the computer can use both DIMMs simultaneously resulting in a speed increase. Traditionally, computers would use multiple DIMMs sequentially as required, meaning the load was not fairly shared.

Many off-the-shelf machines will come with just one DIMM - this is not necessarily a bad thing, but if the dual channel option is available you should go for it.

The other thing to consider here is upgradeability. Make sure there are a couple of slots left for future upgrades.

Step 5: Hard Disks

PC World and many manufacturers sell their products on numbers, i.e. the more space your hard disk has, the better. Wrong. Most people will never use more than 20 - 30Gb of space, so what’s the point in having a 250Gb disk? To be honest, price differences when buying your own disks are negligible so you might as well have as big a disk as is economically viable. In off-the-shelf machines or build-to-order machines, the price difference between different size disks is likely to be much more, so you have an opportunity to save a little money here.

There are two principal things affecting hard disk performance. Storage space is not one of them, and nor is the interface (most people would never notice a speed difference between SATA I and SATA II for instance). Interface speed limits are often theoretical and therefore largely irrelevant.

You should focus on spindle speed, which should be at least 7200RPM and cache RAM, which should be at least 8MB. Hard disks use cache just like CPUs, the more you have, the faster it will be.

If your system supports it, you can buy two identical disks and set them up in RAID mirroring mode. This will effectively write all your data to both disks, giving you two carbon copies of each other. There are two key benefits here: firstly, if one of the disks fails, you still have the other, and; secondly, the computer will be able to read from both disks simultaneously, further improving performance (write speed remains the same). The only downside is that you may have 2 x 100Gb disks, but you will still only have 100Gb space. I always set up RAID like this - it does make a difference.

Be aware that if you are building your own system, Windows XP has no drivers for RAID, so you will often need to create a floppy disk with the driver on it. Clearly, you will need a working computer to do this, and of course a floppy drive on your new machine, whether it be internal or a USB external drive.

Step 6: Graphics card

This is increasingly important as Windows Vista will make heavy use of the graphics card for rendering the screen, much the same way OS X does on Mac. So, even if you don’t plan to play games you should get a reasonable card. I prefer ATi over nVidia as they are usually better value for money and run cooler.

If you are building your own machine to use for graphic design, CAD or similar, buy a workstation card not a gamers card. The ATi FireGL range are good, as are nVidia’s Quadro cards.

If you are buying your machine complete, make sure it has a seperate card not an on-board graphics card. On-board cards are built into the motherboard and share the system RAM. This is not efficient and creates a bottle neck in the machine that will affect overall system performance.

Graphics cards are constantly changing. Don’t bother spending huge amounts of cash on the latest card, find a slightly lower spec for a third of the price. There will never be any games that are only supported by the latest and most expensive cards, so buy cheaper and upgrade at sensible intervals as prices fall.

Step 7: Optical drives

At the moment, the drive to have is a DVD ReWriter. These drives should be able to read CD-ROMs, DVD-ROMs (including movies) and be able to write to both CD and DVD. The price difference is negligible between the various types, so get a DVD ReWriter - they can be extremely useful, particularly for backing up your files.

For system builders, I recommend LG drives. I’ve never had a problem with them, and they are reasonably priced.

Conclusion

This guide is certainly not exhaustive, but I shall be adding to it and refining certain sections over the coming months. All comments are welcomed, and I hope it’s been of use.