Selecting a PC system

Choosing the correct computer system is a difficult decision for home and professional users alike. This is due to the thousands of different products and their ever-changing specifications.

If cost is not a problem, then there are few other problems. You can simply purchase the most powerful computer incorporating the latest technology, with an array of peripherals for every possible use.

In the real world we have financial constraints and have to balance what we want, what we need and what we can afford.

If you only intend to produce graphics for web site use, a minimal system will suffice. After all, the final graphic images will be small. This places little demands on the computer, which need not be fast, need not have vast disk or memory storage capacity and needs only the lowest specification digital camera and scanner.

However, we will be looking for a system specification that is appropriate to the average user who will expect to carry out more advanced work with larger images.



The heart of your computer system is the Central Processing Unit. The speed and design of this chip has a large bearing on the overall speed of your computer. This is normally supported by as large and efficient memory system as possible.

Many everyday applications can be used on machines with fairly low specifications. You can carry out word processing, web browsing, sending e-mail, and so on, with a computer with a slow processor, little memory and not much in the way of hard disk space. Graphic editing and multimedia systems are different. They require lots of power. They are asked to shift and store huge amounts of data. Sound and video files can be huge and a single uncompressed graphic image can now be up to 48Mb. Their sheer size makes it difficult to move them around the system fast enough. Processor speed is very significant for activities such as:

• Batch processing of images
• Processing video clips and large audio clips.
  

The computers currently for sale have CPUs whose speeds range from 500MHz to 1.5GHz. The low end of this market is fine for low intensity use, while the serious hobbyist or semi-professional might be better off with an 800-900MHz chip. The extra premium at the high end of the scale may not justify the marginal increase in overall speed, and so is best left to professionals requiring constant high-speed processing. The serious (and seriously rich) user may also consider a model that has two or more CPUs fitted. This is known as 'symmetric multiprocessing' and is ideal for heavy processing tasks.



Memory chips store your operating system (e.g. Windows), the applications packages that you are running, and the data that is used or created (e.g. graphic images).

Your processor is constantly exchanging data between itself and all of the above. It stands to reason, then, that having a large supply of fast memory will improve your computer's performance. The memory requirements of a particular application are printed in its manual or on the packaging. If the computer uses Windows and Windows-based applications, the machine will need lots of memory.

The memory required to run multiple Windows applications can exceed 128Mb. Windows can run on less memory but is too slow for commercial efficiency. Conversely, the more memory that is fitted, the more efficiently Windows applications will run.

What data can't be held in memory has to be moved back and forward to disk (effective but slow). Therefore, if I had to choose between spending money on a slightly faster processor or on increasing the system's memory, I would choose additional memory every time.

The standard memory fitted in most computers is the 'Dual In-line Memory Module'. It is more reliable than the older SIMM memory module and requires less memory bank slots. Watch out for the emergence of the RIMM (Rambus In-line Memory Module). The first RIMMs are being supplied in newer boards (e.g. i810/820 chipset boards) to support the latest generation of processors. They use RAMBUS technology, which is an extremely fast serial technology (compared to the more usual parallel access).

Memory modules are available in values of 32Mb, 64Mb, 128Mb and 256Mb. DIMM modules are available to the PC100, PC133 or PC200 standard. That means that they can be switched at the rate of 100MHz, 133MHz or 200MHz. Intel Pentiums motherboards work at 100MHz or 133MHz, while AMD CPUs use 200MHz. There are already models on the market that use Rambus modules running at 800MHz.


DISK
It's a golden rule that you will need more disk space than you first predicted. Calculation of the disk's required size is not a simple sum of all the expected applications, since each application will generate its own sets of data. A single Windows application can require upwards of 250Mb of hard disk space just to store its program files. Fortunately, few new systems have less than 8Gb of hard disk space, even for budget entry-level PCs. However, AVI video clips can each require up to 2Gb of storage space. It makes sense to budget for as large a hard disk system as you can afford. But, choosing your disk system for your computer is not simply a matter of looking for the largest capacity model. As important is the efficiency of the disk in saving and recovering data.

The speed of a disk drive is based on

• The time to get to the required data (known as the 'access time')
• The time taken to read that data from the disk (known as the 'data transfer rate')
  

The access time of modern drives range from about 14ms to under 6ms. The data transfer rate depends upon the types of disk interface used and on the rotational speed of the disk (the faster the disk spins, the quicker the data can be read/written). The current range of models has speeds between under 5,000rpm and 15,000rpm.

Consideration should be given to models that have large internal buffers, as this also speeds up disk operations. Current models have buffer sizes from 512KB to 8MB.

Most computers are now supplied with disks that work to the improved UDMA specification. Older drives were UDMA/33, which meant that they transferred at 33Mbps. Most drives supplied with current computers are UDMA/66 (i.e. 66Mbps) models, but a few are now UDMA/100.

For even better disk performance, many users opt for SCSI drives. Although they are more expensive, they provide faster and more stable operations and are a likely choice for multimedia and video editing activities. The average user will find the performance of the newer UDMA to within their price range and their general needs. FireWire drives are just beginning to appear as a super fast disk system

Hard disks hold an incredible amount of information, anything from 10 to over 70Gb. Its almost certain that you will end up adding extra disk capacity as time goes on, so you might consider buying a larger disk drive along with the computer.

ARCHIVING/DISTRIBUTION
The large files sizes of graphic images will soon fill your disk space. They can either be deleted when their use is complete, or they can be taken off your hard disk and saved for future use.

You will need to consider external storage for:

• Creating backups of your important work (in case your main disk breaks down or is stolen).
• Distributing copies of your work to clients, co-workers and friends.
  

You have several options:

• Save the files to writeable CDs. This requires buying a CD writer. This is an ideal medium for distributing collections of work.
• Save the files to large-capacity disk cartridge, such as a 100MB or 250MB ZIP drive or a 120MB Panasonic LS-120 drive. This is the preferred method for exchanging images between users, as the disk can be written and read over and over again.

Save the files to a magnetic tape drive. This is more suited to long-term archiving of material as their retrieval is less convenient and few other users can be expected to have the same type of tape drive.



As your skills expand, you will want to use bigger and better systems. This means that your computer must have:

• Enough free drive bays, to allow additional devices such as CD-writers, extra disk drives, internal Zip drives, card readers, etc. to added at a later date.
• Enough free slots on the computer's motherboard, to allow the addition of new add-on cards such as video capture cards, terminal adaptors, etc.

USB sockets, to allow external USB devices such as scanners to be added. It is often best to buy a tower case system that has plenty of room for future expansion. It should also have a large power supply capable of handling these extra devices (250W or 300W is usually about right).


MONITOR/GRAPHICS CARD
Right at the heart of the system for a graphics editing application is the monitor and graphics card. This is an area where you should look for the best specification you can afford, particularly if you intend spending a lot of time in front of the monitor.

The main factors to consider are:

• Size. You need as large a screen area as possible, so that you can have all your tool bars on screen without hindering the view of the work in progress. Some graphics cards have a 'dual head' output that allows you to connect two monitors to the card. If your software permits it, the tools and images can be shared across two screens. The normal monitor size supplied with computers is 15in and this is adequate for general purposes. The provision of 19in monitors is also common and offers an improved viewing area for the user. For graphics applications such as CAD, artwork, multimedia and DTP, a larger size screen may be necessary - perhaps 19in or 21in.
• Resolution. This is related to the screen size. Larger size screens support a greater number of picture elements and allow true higher resolution viewing.
• Quality. You get what you pay for when you buy monitors. Cheaper models usually have poor screen quality and may be subject to flicker. At the other extreme, flat panel screens are very expensive but provide distinct advantages to the graphics artist:
• They have superb focus.
• They have fixed pixel geometry, so they produce no image distortion.
• They have no problems with misconvergence, such as fringing.

Many models have a rotatable screen, so that you can work in portrait mode (useful for magazine and DTP work). For most users, a 19in CRT monitor is perfectly adequate.

The video card also plays a major part in ensuring image quality. If you are mainly concerned with static images, make sure that the card has enough memory to work at the resolution you want. A 24-bit screen image at 1024x768 needs 4MB of memory installed, while a 1600x1200 image needs 8MB. Graphics cards are available with anything from 8MB to 96MB installed on them.

If you need the card for wider purposes, you should look for features such as fast 3D handling, DVD video handling, and perhaps a TV out socket.


PERIPHERALS/SOFTWARE
The basic computer system will need to be augmented by purchasing other items such as a scanner, graphics tablet, uninterruptible power supply and a range of application software.

Future articles will examine these issues in more detail.

David Dick is an author and consultant on distance learning. His latest book is 'The PC Multimedia Handbook' (see www.dumbreck.demon.co.uk, Right)