FORGET THE MEMORY BLUES
ONE of the problems with the Spectrum is that the Z80 CPU can only address 64K of memory. With 16K taken up with the ROM that only leaves 48K to play with.
The XK upgrade from Television Services of Cambridge goes a long way to solving the problem. Available as a kit, or fitted by the factory, it allows you to page the upper 32K of memory and, when fitted to a standard 48K Spectrum, gives you access to the unused side of the internal memory. The amount of extra memory gained in this way will vary from perhaps a few bytes to, if you are lucky, the full 32K.
In addition up to 128 pages can be added externally. More than two or three will need an extra power supply, which makes a 4Mb Spectrum a reality. As the system only uses A1 to page the memory it will clash with any Sinclair hardware such as Interface One, and, with a few exceptions, be transparent to software.
Fitting the kit is not for the nervous as not only do you have to solder direct to the Spectrum PCB but you also have to cut a number of tracks. That will play hell with your warranty.
The system can be used on its own but it is supplied with a Basic extension that gives you windows and multi-tasking. Each page can be assigned a window, only limited by the number of pages, and each can have a program running in it at the same time. The lower 16K can be used to pass information from one page to another.
The way the commands are used will depend on whether you have Interface 1 fitted. If so they take the form of, for example, *page n or *multi. which swops pages or calls the multitasking. Without Interface 1 RAND USR statements have to be used.
Although, the system should not be affected by commercial software some, notably the Ultimate programs SabreWulf and Atic Atac, cause it to crash. A loader program will soon be made available to overcome that.
For £15.95 for the kit, or £20.95 fitted, both inclusive of VAT and p&p, the system has a lot to offer. Provided more software is made available it could tempt users away from spending £400 on a QL. For more information contact Television Services of Cambridge Ltd., Chesterton Mill, French's Road, Cambridge CB4 3NP. Tel: 0223-311371.