XK Memory Expansion System

Your Computer

Spectrum 48K Television Services £20.95 The XK is available as a kit add-on or fitted to your Spectrum for £5 extra. What it does is hack the Spectrum's memory up into two 32K pages. It also allows you to add up to 128 external pages, each up to 32K, onto your machine. Each page of Ram can have a program running in it, and have a separate screen window dedicated to messages generated by that program. One major problem is that most of the more complex games such as Alien 8 and Lords of Midnight won't run on an XK Spectrum, and being a soldered-in modification, you can't quickly change back.

Sinclair User

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., [redacted].

Personal Computer News

Features 5/5

Documentation 5/5

Performance 5/5

Overall Value 5/5

John Lettice 5/5

MULTI-TASKING ON THE CHEAP It's now possible to have 4Mb of RAM added to your Spectrum. But you'll have to be a wizard with a soldering iron to install the XK expansion, says John Lettice. PRODUCT: XK Expansion System PRICE: £15.95 kit, £20.95 built AVAILABILITY: Television Services of Cambridge, [redacted] It may come as a surprise to you, but it's now perfectly feasible to have 4Mb of RAM fitted and working on a Spectrum. This would probably have come as a shock to Stephen Adams, who is responsible for the hardware that's made it possible, when he soldered his first ZX81 RAMpack years ago. We've all grown a bit since then, and the Spectrum is no exception. FEATURES The XK expansion system is a simple idea - or to be more precise, it's two simple ideas. And the beauty of it is that the entry level modification costs only £15.95 for, if you're lucky, an extra 16K of memory. 'If you're lucky' because some Spectrum aren't 48K at all - they're 64K, and this is a consequence of an early piece of cost-cutting on Sinclair's part. But the failure rate of 64K chips has dropped recently, so you may find you have extra memory you can't use. The XK is intended to give you access to this, and to RAM up to 4Mb, in banks of 32K. IN USE Stephen Adams says fitting the modification is dead easy. I reckon it would be a nightmare. Look at the picture and judge for yourself, but if you're not much cop at soldering, it'd make much more sense to pay the extra to have Television Services do it for you. Once the system's installed you still have a normal Spectrum, so there shouldn't be any problem loading commercial software. The clever bit, actually getting the XK working, is dealt with by the software. This has been written for the system by Andrew Pennell, and is called XP Basic - calling it a Basic may be a little overblown at the moment, but the idea was to get a working system out now, and develop the operating system later. The extended Basic adds a number of functions, but the system's core is its ability to handle extra pages of memory. These are basically 32K banks of RAM that can be switched in and out, and that can run separate programs, is multitask, through interrupts. Think of it this way. Say you want to run a program that ordinarily wouldn't fit in a Spectrum. You can divide it up into subroutines placed on different pages of your expanded memory, and instead of using GOSUB you'd RANDOMIZE USR 26003: PRINT XXX, where XXX is the page number. The program on that page is executed, then you return to the main program. Multitasking is controlled simply by chaining the pages to be multi-tasked together in command line. But wait, you say, if the pages are operating independently how can you update the values of parameters on a page when they may be changed by another page? This is allowed for. The area of RAM from 29000 to 32000 is for transferring data between programs, and it can be used simply by poking the value into this area then peeking it when you need it. Windowing is the other major feature of the new operating system. These scroll automatically, without asking you the Spectrum owner's favourite silly question, 'scroll'?' Obviously windows are important if you're going to be using a multi-tasking system, and these are perfectly usable, although limited. If you move a window over another, the data won't be refreshed when you take it away, but more expensive machines than the Spectrum lack this facility. The multi-tasking also has the odd rough edge, most notably the way that when one of your programs finishes, the others all suspend operation as well. This is fairly easy to deal with, however, and considering the system's low price you'd expect the odd cost-cutting fudge. True, the commands are a little unwieldy, but if you have Interface 1 you have the option to use shortened commands prefixed by '*'. As far as software is concerned, initially the system looks like being catered for by the small but thriving Spectrum business software houses. Andrew Pennell is looking at modifications of Tasword 2 (4Mb RAM disk? All this could be yours) and generally the business programs with a modifiable Basic attached shouldn't present too many problems. To use the system to best advantage, of course, you'll need RAMpacks. These come in 64K batches, and are a bit pricey at £100. If the system takes off, the RAMpack price may come down a little, but think of it this way - for £250 you can get a Spectrum with more user-memory than the QL. VERDICT I'm not going to start complaining about anything useful that costs only £20. The XK is a neat little system with great potential. With such a low price you don't have to find excuses for buying. That said, if a bit of work could bring considerable rewards and if it takes off sufficiently we should be seeing enhanced versions. Television Services was a bit cagey about my suggestion that they give me a custom-built 4Mb Rampack though...

The board fits snugly into the Spectrum - note the soldering to individual pins.