PC Anatomy Explained

JANET HARNIMAN COOK quite literally takes the lid off the PC, and explains why she feels it's the best bet for the future of music.

Until recently, if you wanted to use a computer for sophisticated music or graphics creation, an Apple Macintosh was your only real choice. The Atari ST has done sterling work for musicians in the past, but even its most ardent supporters will acknowledge that it is rather underpowered for today's music requirements. Though affordable and very popular in the business world, the other alternative, the IBM‑compatible PC, was seen as a dreary office machine that was fine for accounts, stock checks and word processing, but a complete non‑starter for more glamorous, creative activities.

Thanks to the endeavours of music software writers, and to some extent, to the introduction of the Windows 95 operating system, this is no longer true. Today's Pentium processor‑based PCs can take on Apple Macs at their own game, and although the cutting edge of MIDI and digital audio editing still remains with the more expensive Power Macs, the gap is closing rapidly. Visitors to my own studio are usually impressed by the speed and versatility of the PC recording system I use, but often, when I suggest that they might try a PC for their own music, I see their eyes glaze over and hear them mutter that they 'never could get their heads around computers.' I'm sure that this mental block stems from a basic lack of familiarity with the way that computers operate. If you, too, feel intimidated by the prospect of using a PC for music, this article is for you.

Admittedly, a lot of effort is necessary. It takes time to learn a sophisticated music package such as Cubase or Logic in depth, and you also have to familiarise yourself with the peculiarities of the PC, but you don't have to learn everything at once — most high‑quality software is designed so that you can make a start almost immediately. Much of the fine detail is optional, and will fall into place once you've mastered the basics.

As you read this article, you will encounter unfamiliar terms, but don't fret — that's what the dedicated Glossary is for, which you'll find elsewhere in this piece. To aid spatial orientation as you read, check out Figure 1 on page 166.

Hardware & Software

Like all computers, the PC consists of two main elements: hardware and software. Hardware describes the physical components of the computer, while software is program data. The two main types of software you'll have to deal with as a musician are the PC's own operating system (the most recent is Windows 95), and the music package you wish to run on the PC. If you've already worked with an Atari program that has a PC counterpart, such as Cubase, you should find the transition relatively simple. The external PC hardware consists of output and input devices — monitors, printers and MIDI Out ports are output devices, while the keyboard, mouse, joystick and MIDI input port are all data input devices.

To learn more, we need to take off the lid, as a significant amount of PC hardware expansion is done by plugging in cards on the inside rather than wiring up boxes on the outside. When the cover is removed from the PC [only after unplugging it from the mains, please! — electrically‑aware Ed], you will see the various components of the internal PC hardware beneath the assorted power leads and ribbon connector cables. These are the Mother board, the Drives, the Cards and the power supply.

The Mother Board

The Pentium mother board illustrated is a standard item with an onboard I/O controller and an Intel 82430 VX version 3 chipset (dated 04‑15‑96) with 256‑kilobyte (K) Pipeline burst cache. The mother board contains the main Processor Chip (or CPU), as well as the BIOS chipset, the ISA and PCI buss slots, the memory slots and the Drive and Port connectors. You don't need to be intimately familiar with all these details, but you do need to know about the slots where cards (of which more later) and memory chips are plugged in.

• THE PROCESSOR CHIP
  When you look at the mother board, you can't actually see the processor chip, as it is hidden beneath the fan‑mounted heat sink. The processor chip is the heart of the PC — it is this component that performs the required mathematical operations on the data presented to it, under instruction from the software being run. The processor's speed and architecture are the main factors that determine PC performance: for example, to run modern MIDI sequencing and hard disk audio applications, a Pentium 90 or higher‑speed processor chip is the preferred option, with the 486 DX50 scraping by as an entry‑level machine. However, for MIDI‑only applications, a 486 is fine.
• MEMORY
  RAM (Random Access Memory) is the computer's main dynamic memory, and comes as small boards called SIMMs or Sticks, that are plugged into the RAM slots on the mother board. RAM is chip‑based and very fast. But it is also volatile, in so far as data is only retained when the computer is switched on. If the power fails, or if the program currently running crashes, any data stored only in RAM will be lost. The purpose of RAM is two‑fold: firstly, it holds a copy of the currently‑active software, usually loaded from the hard disk drive attached to the computer, and secondly, it provides an area for the computer to store numbers as it goes about the business of performing calculations on the input data. Because modern software packages often occupy a lot of memory, and because Windows 95 itself takes up a lot of space, you need a lot of RAM. Too little RAM may result in your software being slow or crashing — or it may not run at all. To comfortably run MIDI + Audio sequencing and digital audio recording applications, 20 Megabytes (Mb) of RAM is adequate, with 16Mb an absolute minimum. This time last year, 16Mb of RAM would have cost you around £400 plus VAT, but thanks to the world slump in RAM prices, you can now expect to buy the same quantity for around £80. Because of the limited number of RAM slots in a computer, it pays to buy the biggest RAM chips or SIMMs (Single In‑line Memory Modules) you can afford, so always go for 16Mb SIMMs or greater — but check with your supplier first to confirm what type, speed and capacity will fit in your particular machine.

The mother board may also contain a slot for Secondary Cache memory. Cache memory is ultra‑fast RAM that sits between the PC's processor chip and the main RAM, acting as a temporary holding area for data subject to repeated access by the processor chip. The variety found on the VX3 mother board is the exotically‑named Pipeline Burst cache, and its job is to make processing even faster. Cache memory is also found on hard drives and printers.

• BIOS
  The mother board also holds the dedicated read‑only memory chips containing the BIOS (Basic In Out System). This is the first tier of the PC operating system, and loads automatically when the PC is powered up, enabling the computer to check and configure the internal and external hardware. All computers need a BIOS of some kind, otherwise the processor chip would power up with no idea what it was supposed to do!

The Drives

As we have seen, RAM is a fast but finite area of memory that forgets everything it knows as soon as the computer is shut down. More permanent storage is provided by magnetic disk drives, which hold programs and files that are not currently active. When you want to stop working on a MIDI sequence or word processing document, the result is always stored on a drive. When you resume work, the file is loaded back into RAM, and you can continue from the point where you left off.

The primary backup storage device on the PC is the hard disk drive, which provides fast data transfer to and from RAM. Old data can be removed and overwritten, and stored data remains intact indefinitely when the power is turned off. Hard disks have the largest maximum storage capacity of all the media listed here — up to around 9 Gigabytes (Gb) per drive, although drive sizes of between 1 and 2Gb are more common. The combination of high capacity and fast access times makes a hard drive a suitable medium for audio and video data storage, as well as more conventional computer applications.

Some hard drives have a removable cartridge and are ideal for archiving audio, including the newer models in the SyQuest range and the Iomega 1Gb Jaz and 100Mb Zip drives. For the storage of smaller program files or data files, the familiar floppy disk is convenient, as it is easily removable and very portable, but its capacity is starting to look rather limited as modern software continues to get bigger. The standard PC High Density (HD) floppy drive has a capacity of 1.44Mb; mine is mainly used for program installation and small file backup.

Optical drives use removable media, the most familiar being the CD‑ROM. These are read‑only devices, with relatively slow access times, but they are cheap to manufacture, as they are internally identical to audio CDs, and they have a large storage capacity of around 680Mb (which is why a lot of large commercial software packages now come on CD‑ROM, rather than on multiple floppy disks). Furthermore, because you can't record new data on a CD‑ROM, or change what's already there, the risk of accidentally corrupting files is eliminated.

Finally, it's worth mentioning that Compact Disk Recorders (CD‑Rs) are starting to find their way into music studio PCs, both for making one‑off CDs and for creating a permanent record of valuable data. They are already widely used by business for archiving or multimedia purposes, and their continually‑falling price makes them particularly attractive to small studio operators, especially as PC software has now become available to allow full Red Book audio CD mastering.

Cards

One of the great things about PCs is that you can plug so‑called cards into the buss slots on the motherboard to make your PC perform a variety of specialised tasks (the buss, by the way, is simply an arrangement of parallel electrical tracks that connects the cards to the processor chip or the computer's RAM). Most Pentium mother boards only have three or four ISA buss slots, and a similar number of PCI buss slots. If you need more ISA slots, you can either invest in a Tree Card or an external ISA card bay, but as we shall see, PC architecture imposes a practical limit on how many cards can be run at once. Every PC needs a video card to run its monitor (unlike modern Apple Macs, where video is accommodated on the mother board), but obviously, the cards of primary importance to musicians are those that handle audio and MIDI — soundcards.

A soundcard samples incoming analogue audio signals and converts them to the digital format used by the PC. It also converts PC digital audio data back to analogue sound when you play back your work, thus enabling the PC to record and play back audio. The soundcard may also include an onboard synth and a MIDI interface. Most audio/MIDI/synth soundcards (see below) plug into the PC's longer ISA slots, while dedicated synth cards, such as Yamaha's SW60XG, can make use of the shorter PCI slots.

If you have a soundcard with a digital input connector (such as DAL's CardD or Digidesign's Audiomedia III card, which has both analogue and digital inputs and outputs), you can transfer digital audio direct to your soundcard via the S/PDIF digital connectors of your DAT or CD player, or from a digital desk like the Yamaha 02R. Some cards (such as Digidesign's Samplecell or Turtle Beach's Maui) even have built‑in samplers. These devices allow you to store samples in RAM plugged into the card itself, then trigger these samples multitimbrally via MIDI, just as you would with a stand‑alone sampler. One of the great advantages of card‑based instruments over their external counterparts is cost, though you also save on wiring and economise on desk space.

For MIDI and 2‑in, 2‑out audio recording, at least one soundcard is required, though for more sophisticated applications, there may be separate cards to handle MIDI interfacing, analogue/digital conversion, and digital audio. There may also be a SCSI (Small Computer System Interface) card for recordable CD drives or any other external SCSI devices, such as additional hard drives.

Ports

Ports are simply connectors for getting data into or out of the PC, and are used by mice, dongles, printers, joysticks, MIDI devices and so on. Connectors for the keyboard and the external serial and parallel ports are located on the mother board (older PCs, for example, those running the Vesa Local bus, will have their drive and port connectors on a separate In/Out — or I/O — card). The second serial port may also be used to carry MIDI data; on my studio PC, it is currently used to receive the MIDI output from a GVox MIDI guitar pickup, though in the past, it acted as the MIDI Out port to a Korg 05R/W. The MIDI interface on a typical soundcard requires an inexpensive adaptor to be plugged into the joystick port, though some cards are turning up with proper 5‑pin MIDI connectors fitted.

IRQ

IRQs, or Interrupt Requests, are one area of PC lore that gives the machine its reputation for complexity, but every computer has to have an interrupt system to operate — such systems regulate the flow of data between the processor chip and peripheral devices such as cards, ports, drives, mice, keyboards, and anything else that needs to talk to the processor. Once a program is loaded, the processor sits and twiddles its electronic thumbs until its attention is demanded by an interrupt request, which will be sent whenever you move a mouse, tap a key or send in a bit of MIDI data from a music keyboard. Although computers can produce the illusion of being able to deal with several things simultaneously, this is solely because of the speed at which tasks are handled — in fact, they can only carry out one operation at a time, and this includes dealing with interrupt requests. Devices are therefore given different interrupt numbers so that they can form orderly queues when they all clamour for attention at the same time. Think of it like the ticket machine at the deli counter in the supermarket, where you're given a numbered ticket, and then have to wait until your number is called.

One problem with the IRQ system is that the number of IRQs is limited to 16 (numbered 0‑15). What's more, the majority are taken up with the basic PC hardware, leaving only four or five available for other devices such as soundcards. You can view the IRQ list in Windows 95 by clicking with the right mouse button on the My Computer icon on the desktop. Click on Properties/Device Manager, and then highlight Computer from the list. Click once again using ther right mouse button to select Computer Properties/View Resources By IRQ (as shown, left). If you do run out of IRQs, it is possible to have two devices sharing the same interrupt, providing they are not active at the same time, though Windows 95 might issue dire warnings if you decide to do this (which you'll have to be brave enough to ignore). I run my digital card on IRQ 7, which is also assigned to the printer port, and it's fine as long as I don't try to use both at once. Windows 95 includes a system known as 'Plug and Play', which is designed to handle the assigning of IRQ numbers to Plug and Play‑compatible hardware automatically. Non‑'Plug and Play' hardware still needs to be configured by hand, which involves checking to see which IRQs and DMAs are free, then fiddling with hardware switch jumpers on the cards to switch the boards to a setting that is still free. See the 'Plug & Pray' sidebar for more details [and for more information on DMAs, or Direct Memory Access addresses, see the 'PC Concepts Explained' box in Brian Heywood's dedicated article on soundcards, which starts on page 180 — Ed].

Operating Systems

Once the BIOS is on line, the main operating system, which is stored on your hard drive, boots. 'Boot' is a computer term derived from the paradox about a person trying to lift themselves by their own bootstraps, but as far as the user is concerned, it means the operating system loads up ready for use.

Although several PC operating systems are available, the most widely used is Microsoft's Windows 95, and now, a year from its introduction, this is settling down nicely. After running it for six months, I'm a fan and find it more robust, faster and easier to use than Windows 3.1. Many MIDI sequencers and audio editors are being released in native Windows 95 versions, and indeed, some of the newest applications will only run under Windows 95, such as the excellent Steinberg WaveLab audio editor (reviewed SOS August '96) or Emagic's Logic Audio (see review starting page 90 this issue). Windows 3.1 is still popular, especially on older, slower systems, and I have a certain amount of sympathy with the 'if it ain't broke, why fix it' brigade, but I think the writing's on the wall for pre‑Windows 95 systems. And with RAM prices now so low, the whinges about how much RAM Windows 95 gobbles up are far less of an issue.

Windows 95 presents a colourful, graphical environment in which you can run your applications and manage the files in your PC. The desktop contains a suite of accessories programs including a text editor/reader, a bitmap image viewer and disk tools, together with MIDI, audio and PC video players. The appearance of the Windows 95 desktop can be tweaked and customised to your personal taste; click on the desktop with the right mouse button and go to Display Properties/Appearance, where you can adjust colour, layout and system fonts. From Background you may choose your favourite bitmap image as your desktop 'wallpaper'. Windows 95 also has good on‑line Help — a feature shared by nearly all Windows programs (one curious exception being Emagic Logic, which still relies on old‑fashioned paper). On‑line help, although very useful, rarely contains the detail found in the application's manual. Unfortunately, the current trend in software marketing has been to scrap the printed manual in favour of an electronic version on the program CD‑ROM. When I recently bought the otherwise amazing Adobe Photoshop v3.05, I discovered that the printed manual is only available as an optional accessory costing over £30!

Conclusion

The PC is now a powerful, affordable and effective platform for MIDI and digital audio applications. It isn't without its complications and frustrations, but now that the leading music software companies are making real efforts to provide stable, easy‑to‑install packages, life is a lot simpler than it was even a few months ago. If you go the PC route, you take advantage of the economies of scale that go with a mass‑produced, mass‑supported machine. As more people become PC owners for this reason, the user base should continue to expand and take manufacturer support with it. In the long term, this should increase competition and, in turn, drive prices down still further, which can only be to the benefit of all of us.