LET'S GET FIZ-ICAL...

Richard Taylor gets to grpips with Primordial Peripheral's disc drive for the 48K Spectrum.

I suppose it was inevitable that someone, sooner or later would come up with a proper disc drive for the Spectrum. Even though Sinclair have launched their famous Microdrive, its distinct lack of availability (now being eased by limited shop sales) and relatively slow access speed (compared to a real disc system) have prevented its domination of the Spectrum mass storage system market.

There is something of a price gap, however, because the 'real disc system' under examination here will set you back nearly £250, close to the cost of two new 48K Spectrums, the only model this drive will work with.

The FIZ system (Floppy disc drive and Interface for the ZX Spectrum, would you believe) comes in two units; the drive itself and, connected by 50cm of ribbon cable, the interface box which plugs into the back of the Spectrum.

The interface contains quite a large assortment of chips powered by an extra voltage regulator - there to ease the load on the Spectrum's already overworked and overheated internal regulator. The disc unit (a Shugart for those who must know) has a separate mains connection, so you may need a 2-way mains adaptor if you're suffering from 'clogged-up' power sockets and what hacker isn't these days? The 9 volt plug from the Spectrum's own power supply goes into the back of the interface box, the old socket being concealed by the interface.

Switch on and the disc whirrs into life. Instead of the usual Sinclair copyright line the screen clears with the message FIZZ S3/540.4 OPERATING FIRMWARE © 1983 Macronics Systems Ltd. There's no loading or saving of the DOS (Disc Operating System) from tape as the necessary software is held in an EPROM.

On power up the contents of the EPROM is transferred to the top 4K of the Spectrum's RAM. With a further 4K being used by the DOS for temporary storage, the top 8K of RAM is technically rendered unusable.

This could've been a major drawback to the system, making useless many programs that rely on that top 8K for certain functions. However, Primordial supply a formatted-disc that carries a special program called 'lodos'.

The program is called up by the command an dos, thus the instruction PRINT USA dos transfers the DOS from high to low memory. Pretty neat.

The DOS itself relies heavily on BASIC variables and USR calls. After switching on the Spectrum the variables as, bs, cs, dir, back, al, bl, cl, zap and nd are initialised to the addresses of machine code routines in the DOS. So, for instance, PRINT USR dir gives a list of what is on the disc - as well as an indication of the amount of storage capacity and the main disc title. The USR statement returns the number of any error that might have occurred and there is a comprehensive and helpful set of error codes.

The DOS has facilities to save and load BASIC programs, machine code programs (there's an auto-run facility for machine code) and arrays. It is also possible to format new discs, erase files or make back-up copies of discs. Some commands need filenames or other parameters passed to them. This is done by assigning the BASIC variable f$ with the name before typing in the USR statement. For instance, LET f$ - = "Graph" : PRINT USR bs saves a BASIC program onto a disc called "Graph". The commands can be used equally as well in programs as they do as direct commands.

The drive uses single-sided, single density discs; each one capable of 109K of user-available storage. A disc is formatted using the nd command.

One of the 40 tracks on the disc is used by the DOS to store the directory, leaving the user with 39 tracks; each one with a capacity of 2816 odd bytes. One of the idiosyncracies of the system is that a file will occupy at least a complete track even if it is only a few bytes in length - therefore placing a maximum limit of 39 files per disc.

The actual operation of the disc was extremely fast and reliable. The documentation, although brief, was adequate and well presented.

The FIZ system represents value for money if you use your Spectrum for program development or for some sort of data handling. I suspect, however, that the majority of users do not desperately need the added flexibility (and expense) of a proper disc system and would probably do better with a Microdrive.

The system will come into its own when more software is available to run on it. Some games material is available but, as I said, the price tag makes the FIZ a games system in the 'executive toy' class. Primordial have recently announced a word processing disc (based on old 'Tasman' WP) and have an assembler in the works.

FIZ costs £249.95 from Primordial Peripherals Ltd., 89 Herne Road, Bushey, Herts, WD2 3LP. The interface unit can be bought as a separate item for use with other disc drives, price £79.95.