Memopak HRG

Sinclair User

Stephen Adams

ADVANCED GRAPHICS FROM MEMOTECH Memotech has been producing RAM packs for some time but also produces a keyboard for the ZX-81 and a hi-res pack. The keyboard does not require the user to dive into the machine to fit. Its interface module goes into the back of the ZX-81 like all the other modules and the keyboard is on a 7in. cable emerging from the end of the metal box. It provides only 40 keys - no space bar - and the keys tend to echo inside the box, but it works well. It would be very useful to the non-technical user and does net invalidate the guarantee. The hi-res pack - HRG - requires the use of at least a 16K RAM pack in which to store its, high-res pages. Depending on the size of memory, more than one 6,337-byte page can be stored. The pages must be stored outside the normal memory above RAMTOP. The routines to control the screen are in a 2K EPROM from 8K-10K and use certain reserved Basic variables to transfer information to the routines. Twelve variables are required to be set up to make full use of the syStem; one of the Z$ is used to contain one of 30 commands. The screen must first be set up by allocating variable V to the start of the video page, Z$ to 'STARCH' and calling the user routine via RAND USR 8912. That then sets up the screen, clears it and changes the screen from the Sinclair version. You can then see only the hires screen, no INPUTS or commands are visible, and PRINT, PLOT and the like will appear on the Sinclair screen. To return to the Sinclair screen you must either press the black button on the side of the hi-res unit or set Z$ to 'Basic' and call the user routine again. All commands are given in that way through the same USR call. X and Y variables determine the plot position, X being in the range 0-247 and Y is 0-191. Lines can be drawn from point P/Q to X/Y using "LINE";"UNLINE" unplots them. It is a useful device but one which is not easy to learn to use. Many variables have to be set and re-set during the program for it to work. Error codes are given but things like the scroll commands can crash the system if they are not used properly. The casing is stylish and strong and Memorech includes Velcro strips to stick the packs to the ZX-81 to stabilise them. All the Memotech packs are moulded to fit the back of the ZX-81 and each other. The Memotech keyboard costs £49.95 and the HRG pack £39.90. They can be purchased from Memotech Ltd, [redacted], or from larger W H Smith branches.

Memopak HRG