IDEAL HOME DISK DRIVE
IN RECENT months there have been a number of disc systems appearing for the Spectrum, not to mention the Microdrive. One of the first was the Viscount system from Interactive Instruments.
The system comprises an interface which plugs into the back of a 48K Spectrum and a 5.75in. Shugart disc drive, complete with connecting cable. Interactive can supply an extension cable if necessary if you want to add a printer interface, for example. Also the interface will support only one drive and that has only single-sided discs but it manages to squeeze more than 107K on to them.
Setting up the system is very straightforward. On power-up the contents of the EPROM is loaded into the upper 8K of memory and a number of extra variables are added; they occupy another 110 bytes. Those variables are used to call the various functions of the interface.
The first step is to format a new disc, which is done by entering the command PRINT USR nd. Once formatted the disc will have 40 tracks, each 2,816 bytes long. The first track is always taken up with the directory, so you are left with 39 tracks, a total of 109,824 bytes of storage.
Both Basic and machine code can be made to auto-run; code can also be made to load into a different area from the one from which it was saved. The way of filing f$ for arrays is a little complicated and arrays also have one major disadvantage.
Each time an array is saved you are limited to a length of 2,816 bytes, so if you were using a program which uses a string of 28,000 characters you would have to save it in pieces.
In use, the system is at least twice as fast as a Microdrive but the penalty is that it uses a good deal of RAM space.
That means that although it is ideal for business you cannot use programs such as Tasword or Masterfile on it. Transform Ltd, however, can supply some of its software on disc.
Overall, the system is ideal for home users who write their own programs or as part of a development system. The system can be obtained from the Spectrum chain of shops, costing £245 inc. or from the manufacturer, Interactive Instruments, Ltd, Unit 6, Pilot House, King Street, Leicester.