The recently launched Amstrad computer looks set to dominate the low cost micro market during the latter half of this year. With Gary Evans.

The Amstrad name is almost synonymous with low cost, rack hi-fi systems but the launch of the company's CPC464 computer means that, within a couple of months, the trademark will equally well be associated with one of the best value computer systems yet to appear in the UK. Alan Sugar, Amstrad's Chairman, has extended the marketing approach that proved to be so successful for audio products and has come up with a machine that offers remarkable value for money when compared to the current crop of home micros. In addition, the philosophy of selling a complete package is evident in the way in which the components of the CPC464 are packaged.

The base 464 system consists of the computer keyboard and processor unit, which features an in-built cassette data storage unit and a high resolution green screen monitor. The price for these two units is only £220. This is about the same price as some of their competitor's machines but those do not include either monitor nor cassette desk. For an extra £100 the 464 will include an RGB monitor but Amstrad predict that many people will opt for the lower cost package and use an optional £30 modulator that will display the computer's output on a standard colour TV for those occasions when a colour display is essential.

The specifications of the Amstrad machine combine all of the best features of the micros that have proved successful over the past year or so. 64K of RAM is standard as is a flexible and fast BASIC. The keyboard is a full travel "typewriter" style design, none of the cheap rubber keys that have often been the major downfall of systems designed down to a price. The video display offers features that should meet most requirements. An 80 column mode, ideal for word processing or spread sheets is supported by 40 x 25 and 20 x 25 modes. The colours available in the various modes range from 16 in the 20 col. mode, through four in the 40 col. display, to just two when operating with 80 cols. Expansion ports are well in evidence with both joysticks and Centronics printers catered for. In addition all of the Z80 processors control, data and address lines are buffered and made available on an edge connector at the rear of the 464. Each of the various features mentioned here deserves far more space than is available here but this is not meant to be a full review of the machine. However for many of those of us concerned with electronic music, the sound generating section of the computer is of most interest and the rest of this article will concentrate on this area of the computer.

Sounding Off

The sound generating section of the CPC464 is built around the familiar AY-3-8910 chip and it therefore comes as no surprise that the machine offers three tone channels and one noise output. However a nice touch is the way in which the three channels, designated A, B, and C have been mixed to give a pseudo-stereo output. The signal at the audio output features the A and ½C on the right channel although all the signals are combined for reproduction via the computer's internal speaker.

The primary command associated with sound generation is, and this will not come as too much of a shock, SOUND. The command takes the form:

SOUND G, H, I, J, K, L, M

This may look rather complex but in fact the only mandatory parameters are the G and H values. All the parameters are integer values and are responsible for controlling channel status (G), tone period (H), duration (I), volume (J), volume envelope (K), tone envelope (L), and noise period (M).

Some of the above options are self explanatory but others require rather more in the way of explanation, in particular the channel status parameter. This introduces the concept of a rendezvous. The facility allows the sounds produced by the various sound channels to be synchronised. It's useful when, for example, reseting the timing of continuous notes where a tune breaks or 'rests' do not occur simultaneously on the different channels. The envelope command can call on any one of 16 different envelopes of which 15 can be defined by the user-envelope. Nought cannot be modified and is set to produce two seconds of output at the currently defined volume level.

The command to specify an envelope takes the form:

ENV N, P1, Q1, R1, P2, Q2, R2, P3, Q3, R3, P4, Q4, R4, P5, Q5, R5.

Another daunting definition but once again only the envelope number and a minimum of one complete section is mandatory. The sections are defined by the parameters associated with the P, Q and R parameters. P defines the step count (range one to 127), the step size (range -128 to -127) and R for the pause time (range 0 to 255).

Combinations of these parameters allow the production of an almost infinite number of envelopes producing every conceivable type of sound.

The tone envelope has exactly the same format as the sound command with the P, Q, and R parameters of the former being replaced with Tn, Vn and Wn (in the range 0 to 15). This command creates small variations in the frequency of the note being sounded, in other words a form of vibrato.

Sound Design

The Amstrad offers a sound capability that is amongst the most versatile of those found on home computers. Similarly, its performance in other respects is as good as, or better than, the majority of the machines which are at present in the best seller lists. If Amstrad can get enough of the computers onto the high streets they are almost certain to have a winner on their hands. The reaction of other manufacturers, in particular the likes of Commodore, Dragon and Oric is likely to be an exercise in price cutting. It will be an interesting few months and there should be a lot of cheap computers available later in the year!