More facilities is the attraction of this device - the catch is that it costs more too. But it's worth paying extra, says Stuart Cooke

The Sinclair Spectrum has never suffered from shortage of add-ons - in fact, if anything it suffers from a surplus of peripherals. One of the latest fads in add-ons for the machine is fast/mass storage devices, ranging from Microdrives to the more expensive floppy disks. One of the latest disk systems is the Discovery 1 from Opus.

The Discovery is supplied as either a single or dual 3.5" system in a smart looking metal case. The Spectrum sits on a metal base and plugs into the edge connector on the unit, with only a single screw to hold it. The unit features a joystick port, parallel printer connector and video socket, as well as the usual through connector for other add-ons.

Setting up couldn't be simpler - just screw it onto the main unit. The Spectrum power supply is no longer needed, as the Discovery powers the micro. Its supple is built into the drive and has a moulded plug on the end for connecting it into the mains.

To get a picture from your Spectrum, you may want to plug it into a television. Unfortunately the back of the disk drive obstructs the TV socket on the computer, making it a tight squeeze. The same applies to the cassette leads, as their sockets are also obscured.

To be fair, the leads do fit but a lot of strain is put on the connectors. At the rear of the machine is a video socket, which allows you to plug your Spectrum into a composite video monitor.

The right-hand side of the disk drive holds all the interfaces. The plug for the joystick is the standard 9-pin Atari style, which means that almost every commercial joystick can be used. Before you load up a program however, you must remember to turn it on - rather annoying when you've just spent five minutes loading a program only to find that the joystick will not function!

The FORMAT command turns the joystick on and off and is read by use of the IN 31 instruction. Quite by chance, this happens to be the same as the Kempston joystick interface.

Next to the joystick connector is a parallel printer connector. Unfortunately, this is not a standard socket but an edge connector, which means that you will have to buy a special cable. A diagram of the connector is given in the manual so that you can make your own or find one easily. This port not only allows you to send data out to a parallel printer; it also reads data from the port, so you could connect your Spectrum to another machine or any other device with a parallel port.

Finally, the standard Spectrum edge connector allows you to connect other Spectrum peripherals without having to disconnect the drive.

The disk drive uses the increasingly popular 3.5" disks. Control is by means of the same commands as the Sinclair Microdrives. In fact, the only differences are that some of the commands have been extended to make use of the greater facilities offered by the Discovery.

If you have ever used a Microdrive you will feel at home with the Discovery. Programs that have a Microdrive option can be easily transferred onto the disk drive from tape. Tasword was transferred, following the instructions in the manual and the disk drive's increased speed, plus the ability to use the Spectrum with a monitor improved its performance.

Not only can you load and save programs to the drive but as with Microdrives, you can use it for file handling. A file can be OPENed to disk and data stored in it in a sequential format i.e. one character after another.

The problem with this method of file handling is that if you wish to find a sequence of characters stored in the middle of the file, you have to read every character till you find the one you want.

However, the Discovery does allow you to set up random access files, enabling you to read from any point in the file and make any alterations without having to read in the file. You must specify the length of every record that you are going to use and the length of the file, so the disk drive knows how much space it should allocate to your file. For example, using the command OPEN #5, "m";1;"fred" RND 10,10 would allocate the file fred ten records of ten characters. There's however a special format for setting up random access files - OPEN #5,"m"i;"fred" RND 10,-1 which would allocate half of the available disk space to the file fred allowing ten characters per entry.

Moving the pointer around a file is also extremely easy. An expansion to the POINT command, POINT #5,10 moves the pointer to the tenth record in the file associated with stream 5. This facility enables you to set up a database, and make any changes when needed without worrying about memory.

A RAM disk facility has also been provided. This allows you to use an area of the Spectrum's memroy as if it was a disk drive. Access to smaller files is extremely fast, as the Operating System doesn't have to look on the disk for the programs. To use the RAM disk, you must lower RAMtop on the Spectrum to its new value with the normal CLEAR command and then FORMAT the reserved RAM by calling it device number 5 in a FORMAT statement.

The Operating System is also completely compatible with tape. When you add a Microdrive to a Spectrum, a fair amount of the available memory is set aside by the Interface 1 for the Microdrive maps and system variables. The Discovery 1 appears to use none of the Spectrum's RAM. Commercial software should run with the drive present.

The Opus Discovery 1 is certainly one of the best add-ons around for the Spectrum and does the jobs usually achieved by adding several boxes onto it.

Features 5/5
Documentation 3/5
Performance 4/5
Overall value 4/5